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Bird Ecology and ConservationA Handbook of Techniques$

William J. Sutherland, Ian Newton, and Rhys Green

Print publication date: 2004

Print ISBN-13: 9780198520863

Published to Oxford Scholarship Online: September 2007

DOI: 10.1093/acprof:oso/9780198520863.001.0001

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Conservation management of endangered birds

Conservation management of endangered birds

Chapter:
(p.269) 12 Conservation management of endangered birds
Source:
Bird Ecology and Conservation
Author(s):

Carl G. Jones

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780198520863.003.0012

Abstract and Keywords

This chapter describes how conservationists can intervene to help save endangered species. The approaches used include supplementary feeding; disease control; predator control; and intensive management of nesting birds, such as manipulating the clutch or brood, reintroductions, and translocation.

Keywords:   nest sites, disease control, nest manipulations, reintroductions, tranlocations

12.1 Introduction

There is a long history of managing endangered birds. Techniques were first developed for game bird management and later adapted from falconry and avi-culture to a wide range of species. Endangered birds have usually been managed at the population level by enhancing habitats, providing artificial nest sites or food, or controlling predators and pathogens. Manipulating the productivity of breeding birds has a more recent history and techniques are still being developed, especially in North America, New Zealand, and Mauritius.

In Mauritius and New Zealand, work on endangered birds on the mainland and on small offshore islands has involved habitat restoration and whole ecosystem management. This has led to integrated restoration programs addressing the ultimate environmental (e.g. habitat destruction and degradation), and the proximate demographic factors (poor survival and reproduction) that cause endangerment.

12.2 Process in the restoration of endangered species

The restoration of an endangered bird population usually starts with a synthesis of existing knowledge of the species, its life history and numbers, followed by an evaluation of the problems it faces. Research is often necessary to fill important gaps. The goal of the conservation effort is to alleviate the factors that prevent the population's recovery. With Critically Endangered and Endangered species, that by definition have small populations, it is important to increase the population as rapidly as possible and hence address the proximate limiting factors while at the same time working toward rectifying the ultimate causes of the species rarity.

(p.270) The level of intervention and management is dictated by the rarity of the species. The IUCN criteria for threatened species; Critically Endangered, Endangered, and Vulnerable (IUCN 1994) provide a guide to the degree and intensity of management required. The process of restoration goes through several stages when the emphasis and priorities may change. Five broad overlapping stages provide a conceptual framework in which to develop restoration work.

12.2.1 Stage one: know your species

For many endangered species, we still know only cursory details of their life history and biology. Several early attempts to restore populations failed because not enough was known about their ecology to address, in an effective manner, the problems they were encountering. Thus the first stage is to know the life history, ecology, distribution, and numbers of the species concerned. A study of a small number of pairs will answer questions about the diet, habitat needs, and nest success. Studies of captive individuals have often been used to supplement studies in the wild, if necessary using related species to develop techniques and train staff.

12.2.2 Stage two: diagnose causes of population decline and test remedial action

There are several approaches to this problem (see Green 1995, 2002; Sutherland 2000 for useful background). Collation of existing knowledge is essential to assess previous distribution and population trends, especially information on mortality, productivity, causes of breeding failure, age structure, survival in different habitats, the impacts of weather, and other factors of possible relevance. Review any ecological changes that may have impacted upon the species, especially those brought about by recent human action.

From these exercises and information learnt in stage one, it is possible to list all the possible reasons for decline and to propose hypotheses on causes of rarity that can be tested in the field. For species where nest-sites might be limiting, this possibility can be tested by providing artificial sites or enhancing natural ones. Where food might be limiting, the provision of supplemental food, and monitoring the response of the population can give an indication of the extent and nature of the problem. (For details of previous experiments involving food and nest manipulations see Newton 1994, 1998).

For many threatened bird species on islands, it can be assumed a priori that known exotic mammal predators (often rats and feral cats) are likely to be affecting bird populations. On the basis of past experience, these species can be considered guilty until proven innocent, but data must be collected during any control program to evaluate its effect, and management should be modified accordingly. All management needs to be based on evidence.

(p.271) It is often useful to keep a close watch on wild pairs, monitoring their behavior, anticipating and reacting to problems that may affect them. Such activities help to provide insight into the problems wild pairs face, and may enable the rescue of eggs and young from failing nests. They may also give evidence on how factors such as food, weather, and parasites affect the birds involved.

This is the stage when hypotheses are proposed and tested empirically, in order to identify the threats and to evaluate different approaches to improving productivity and survival. Staff are trained in the techniques of intensive management. These are the preliminaries to the next two stages.

12.2.3 Stage three: intensive management

Usually only applied to critically endangered populations, this stage is aimed at addressing limiting factors identified in stage two. The focus is on maximizing the productivity and survival of each individual, in order to increase numbers as rapidly as possible, and at the same time maintain as much genetic diversity, and where possible to avoid inbreeding. Intensive management may involve captive breeding and release, translocating birds onto predator free islands (where they can be carefully managed), and egg and brood manipulations. Intensive management requires great attention to detail, and may need help from avian pediatricians, veterinarians, reintroduction specialists, and other experienced support personnel (climbers, trappers, predator control, and captive-breeding personnel).

12.2.4 Stage four: population management

Populations that have not reached critically low levels can be managed without resorting to any form of intensive care, assuming that management actions enable numbers to recover to safe and sustainable levels. Management is undertaken at the population level, and is aimed at increasing a population's growth by addressing previously identified limiting factors. Typical approaches would include protection against human persecution, provision of habitat or secure nest-sites, supplemental feeding, predator or disease control, translocations to more suitable areas (but without the intensive management of Stage three). This is the stage when numbers are sufficient for detailed research to identify the most important factors that limit the population. Management is driven by these findings, and for many bird species may have to be long-term. The staff need to include researchers.

12.2.5 Stage five: monitoring

It is important to carefully monitor populations of conservation concern, both during and after restoration, so the impacts of the management can be evaluated. Consistent long-term population monitoring requires, at the least, continual (p.272) assessment of numbers and distribution, and if possible also of productivity and survival.

These various components of species restoration may seem self-evident, but a surprisingly large number of restoration projects have proceeded without a clear and coherent knowledge of the problems and a plan of how to address them. Often the ultimate goal is clear but the intermediate steps are less evident. A clear step-by-step approach to species conservation allows managers to plan the work as a series of short-term achievable goals, where the roles of managers, technicians, consultants, and scientists can be clearly defined.

12.3 Broad population management approaches

Within their particular habitats, most bird populations are naturally limited by a relatively few variables, of which availability of food and safe nest-sites, predation, competition, and disease are among the most important (Lack 1954, 1966; Newton 1998). In the absence of human impact, it can be assumed that one, or an interaction of several such factors, will be limiting the size of most bird populations. The species may respond to a broad approach simultaneously addressing several of the more likely limiting factors. In declining or very small populations, productivity or survival may be enhanced by management without fully understanding the causes of population decline. This approach was applied to the Chatham Island Black Robin Petroica traversi and Echo Parakeet Psittacula eques restoration programs. The species' extreme rarity was addressed by providing some supplemental food, enhancing and protecting nest-sites, controlling/excluding predators, competitors, and parasites around nest-sites (Butler and Merton 1992; Jones and Duffy 1993). These management actions were implemented, even though it was not known at the time what was limiting Black Robin and Echo Parakeet populations, and which actions were the most important. In very small populations, empirical evaluation of the factors affecting numbers can often be the most efficient approach for understanding the causes of decline or rarity, reacting to problems as they are identified. The Chatham Island Black Robin, Mauritius Kestrel Falco punctatus, Pink Pigeon Nesoenas mayeri, and Echo Parakeet had declined to such low numbers that there was no other option available.

When attempting to restore a population, the temptation to focus exclusively upon the causes of past decline may not always be necessary (Goss-Custard 1993; Green 1995). This might in any case not be correctable in the short-term, as with habitat loss. But a species that is declining due to high adult mortality may be saved by boosting its productivity, and this may be achieved by improving its food supply or nest-sites.

(p.273) In restoring critically endangered species, the initial aim is to address the proximate causes of population decline to prevent extinction and to boost numbers to a more viable level, while the long-term goal is to address the ultimate cause of decline and rarity, such as habitat destruction. Many projects flounder by failing to differentiate between the proximate and ultimate limiting factors, because the remedial actions required to address them are different.

12.3.1 Supplemental feeding

Supplementary feeding has shown a range of effects upon wild bird populations, including:

  • Increasing the percentage of birds breeding

  • Improving the productivity of individuals by inducing earlier laying, increased clutch size, or increased chick survival

  • Improving juvenile and adult survival.

Such responses clearly demonstrate the importance of food supply in influencing individual performance, and can in turn lead to increased numbers (Newton 1998). Not surprisingly, supplemental feeding has been a main component in many bird restoration projects, often implemented alongside other measures. In particular, it may help to support other forms of management. Some Mauritius Kestrel pairs, that had been given foster young to rear, were provided with extra food (dead passerines), which allowed them to rear larger broods than normal. At Peregrine Falcon Falco peregrinus nests, when one of the pair was killed, the partner still managed to rear the young when given dead Coturnix quail (Craig et al. 1988; Walton and Thelander 1988).

The recovery of the central North America population of the Trumpeter Swan Cygnus buccinator is attributed to supplemental feeding during the winter. This population declined to about 130 birds in the 1930s. The swans fed on submerged aquatic vegetation and in late winter, when most ponds froze over, many swans died from food shortages. Annual supplemental feeding of grain was started in 1936. The level of winter mortality dropped dramatically and within 20 years the population had increased to about 600 birds (Archibald 1978a).

Winter feeding programs have also greatly benefited populations of cranes. A nonmigratory population of Red-crowned Cranes Grus japonensis in southeast Hokkaido was stable at about 30 birds. In the winter these cranes used to feed along streams, but in the unusually cold winter of 1952 the streams froze and so the cranes were given grain to prevent them from starving. This winter-feeding became a tradition and within 15 years the population had increased to about 200 birds, and has stayed around that level ever since. Similar population (p.274) increases have been recorded in response to winter feeding programs in Hooded Cranes G. monacha and White-napped Cranes G. vipio (Archibald 1978b).

Some species, such as the Trumpeter Swan and cranes may be easy to feed, because they readily take grain. However, others are more difficult: attempts to feed wild Echo Parakeets, for example, were surprisingly largely unsuccessful. After trials with a range of food types offered in various ways, the best that was achieved was to feed a small number of individuals for a few weeks only (Jones and Duffy 1993). Captive-reared and released Echo Parakeets proved easier to feed and took a pelleted diet from hoppers. Young ones reared by released birds learned to use the hoppers, and thereafter some wild birds also started using the hopper, presumably through social facilitation. Birds feeding at the hoppers reared larger broods than the other wild birds, and readily accepted and reared fostered young. Even lone female parakeets successfully reared young.

Supplementary feeding has proved important in the restoration of the New Zealand Kakapo Strigops habroptilus. The females fed from hoppers placed in their home ranges, each female being individually managed. It is hoped that the provision of supplementary foods will promote and sustain regular breeding (James et al. 1991; Powlesland et al. 1992), and so far it has increased breeding frequency and enhanced chick survival (Elliot et al. 2001).

12.3.2 Enhancing nest-sites and the provision of nest-boxes

In many bird populations, nest-sites are limiting, especially for species that nest in tree cavities or on cliff ledges (Newton 1998). In addition many birds have only poor sites, which do not protect them against predators or adverse weather. Many species have increased in numbers after the enhancement of existing nest-sites or creation of new ones, thus demonstrating the limiting effect of nest-sites on breeding density and success (Newton 1998). Many different artificial nest-sites have been successful, such as nest ledges and cavities for cliff nesting species, platforms, and artificial stick nests for tree nesting species, artificial burrows for terrestrial hole nesters, rafts for wetland birds, and nest-boxes for a whole range of cavity nesting species.

In the absence of high quality nest cavities, Echo Parakeets and Mauritius Kestrels tried to nest in sites prone to predation, flooding, or overheating. Consequently, it became policy to improve nest cavities that were considered suboptimal. At cavities frequented by kestrels any debris, such as old nest material or loose rocks lying on the cavity floor, was replaced with washed gravel. If necessary, the cavity entrance was modified by placing rocks to provide landing spots or perches for the kestrels, and in exposed sites rocks were arranged to provide shade and shelter. Pairs subsequently raised young in many of the modified (p.275) cavities. Sites that were unsuitable because they were easily accessible to predators were permanently blocked (Jones et al. 1991). The use of nest boxes has greatly increased the numbers of breeding kestrels on Mauritius by providing nest sites in areas previously lacking them. In one subpopulation exposed to a shortage of natural cavities in the 2002–03 season, 27 (63%) out of the 43 known pairs used nest-boxes.

Nest cavity modification has been a major feature of the Echo Parakeet restoration work. Cavities were modified according to the characters of the most secure and successful sites, with changes to every occupied cavity, and others where parakeets were seen prospecting. In the 2002–03 season, there were 21 breeding pairs, 17 in modified tree cavities and 4 in nest-boxes.

Any nest-sites in rotten trees that were in danger of falling were destroyed, while others were reinforced and repaired. In sites that flooded in wet weather, drainage holes were inserted, or weather guards were placed around the entrance to keep out driving rain. Shallow cavities are deepened to at least 70 cm. An entrance door was built into the side of every cavity, so that field-workers could gain access to eggs and young. The substrate was changed in all cavities before the breeding season, and again every week or two during the nesting period, in order to maintain hygiene and to prevent the build up of nest parasites.

In some cavities, the size of the entrance hole was reduced to exclude White-tailed Tropic Birds Phaethon lepturus, (which have plenty of other sites), in order to increase the numbers available to parakeets. At some cavities a network of branches was placed near the hole, to prevent long-winged, non-perching tropic birds from gaining access to the cavity, but to provide perches for adult and newly fledged parakeets. In all nest trees, predator guards in the form of smooth plastic sheeting wrapped around the trunk were fixed and any interlocking branches from neighboring trees were pruned off to discourage monkeys and rats. Between 1987 and 2002, 45 modified cavities were used between one and seven times.

Nest-site enhancement has been an important component in the restoration of the Puerto Rican Parrot Amazona vittata. For this species nest-sites were found to be in short supply and accessible to predatory Pearly-eyed Thrashers Margarops fuscatus, a recent colonist of Puerto Rican forests (Snyder 1978; Wiley 1985; Snyder et al. 1987). Some cavities were used for 20 years or more, as good sites that were both secure and of suitable size were scarce. The modification of nest cavities was also a component of the California Condor Gymnogyps californianus restoration project, where cliff cavity floors were leveled and rock baffles built for protection (Snyder and Snyder 2000).

The Echo Parakeets on Mauritius would readily accept modified cavities, but for many years refused to use nest-boxes, until at last a design was found that was (p.276) acceptable to some wild birds. Released parakeets, and wild males paired to released females, have readily accepted nest-boxes. The reluctance with which the wild Echo Parakeets have accepted nest-boxes is mirrored by the experience of others working with wild parrots. For example, efforts with three Amazona parrot species in Mexico, with St Lucia Parrots Amazona versicolor and Puerto Rican parrots have almost all failed (N. Snyder personal communication). However, by contrast, Blue and Gold Macaws Ara ararauna readily accepted nest-boxes (Munn 1992) as did Green-rumped Parrotlets Forpus passerinus(Beissinger and Bucher 1992). Nest-boxes increased the number of breeding pairs of the Green-rumped Parrotlet, and were more secure than natural holes. Birds nesting in boxes had more frequent and larger broods. This is a common finding with nest-boxes where predation rates are often lower. In addition cavity size may influence clutch and brood size.

Artificial ledges and cavities have been successfully constructed for many cliff nesting bird species, including Northern Bald Ibis Geronticus eremita (Hirsch 1978) and various raptors. In Germany artificial sites suitable for Peregrine Falcons Falco peregrinus have been made in quarries and cavities have been blasted in cliff faces (Hepp 1988) so that about 80% of eyries in the Black Forest area were in artificial sites, where breeding success was “distinctly higher than in natural nests” (Brucher and Wegner 1988).

Competition over cavities can be severe. The size of the entrance hole is often important, and for most species the smallest hole through which they can enter is the safest, since this excludes larger species. Minimizing the entrance hole was used to exclude White-tailed Tropic Birds, which were competing for nest-sites with the smaller and much rarer Bermuda Petrel Pterodroma cahow (Wingate 1978). The exclusion of the tropic birds led to improved breeding success and numbers of petrels, with pairs increasing from 18 in 1962, when management first started, to 26 in 1977 (Wingate 1978) and an estimated 180 birds (53 breeding pairs) by 1997 (Stattersfield and Capper 2000).

Nest-boxes are widely used in Europe and have resulted in increases in populations of many hole-nesting birds, including Pied Flycatcher Ficedula hypoleuca, Collared Flycatcher F. albicollis, Redstart Phoenicurus phoenicurus, various tits Parus spp., Tree Sparrow Passer montanus, and Starling Sturnus vulgaris (Newton 1994). In North America nest-boxes have resulted in a steady increase in the populations of Bluebirds Sialia spp. (Zeleny 1978, Newton 1998). Nest-boxes represent an alternative to natural hollows, but are not always an adequate replacement because they do not reflect the diversity of natural hollows (Gibbons and Lindemayer 2002). Some species prefer natural cavities to nest-boxes (e.g. Treecreeper Certhia familiaris), and for these more research is needed on nest-box design.

(p.277) 12.3.3 Disease control

Parasitic disease was once considered to have little impact on most bird species, only in exceptional circumstances being a major cause of mortality (Lack 1954, 1966). We now know that disease is an important component in the population limitation of many birds (Newton 1998), while the role of pathogens in threatened bird populations has been reviewed by Cooper (1989). Introduced diseases may have profound impacts on native hosts, a well known example being the introduced avian malaria and pox in Hawaii, which limits the endemic honey-creepers to upland areas where mosquito densities are low (Van Riper et al. 1986). The Pink Pigeon on Mauritius suffers high nestling mortality from trichomoniasis, caused by a flagellate protozoan believed to have been introduced to Mauritius with exotic doves (Swinnerton 2001).

A knowledge of the disease profile of the focal species is often useful so that:

  • The likely effect of disease upon the survival and breeding of the species can be understood.

  • The disease can be combated as a cause of poor breeding or survival.

  • New diseases can be excluded by quarantine measures.

A health audit of a wild population of a managed critically endangered species needs to be implemented during the early stages of the project (Stage 2). Surveys of disease, and knowledge from similar surveys on related species, provide useful indicators (Joyner et al. 1992; Gilardi et al. 1995). It is important to find what diseases are present, how these may be influencing survival and productivity, and how they can be managed to minimize their impact.

The species should be screened for diseases known to be important to closely related species (where such information is available). For example, pigeons are prone to trichomoniasis and parrots to several viral infections such as psittacine beak and feather disease and poliomavirus. There also needs to be a more general screening for parasitic diseases to look for ecto-parasites, blood parasites, and endo-parasites. Fecal samples should be screened for pathogenic bacteria, with selective culture for fungi, yersinia, and chlamydia. All dead adults, chicks, and eggs should be postmortemed in an attempt to understand the causes, and also the patterns of mortality (Greenwood 1996).

A careful health audit of both wild and captive birds enables measures to be taken to avoid transmission of disease from captive to wild populations and vice versa, or from one species to another. Where there are in situ captive facilities ideally these should be for single species only, and where other species are held in the same place, they should be screened to avoid transmission of disease to the (p.278) focal species. Young captive Pink Pigeons reared by domestic pigeons Columba livia died when they contracted pigeon herpesvirus from their foster parents (Snyder et al. 1985).

Birds intended for reintroduction should be raised and kept away from unnecessary contact with other captive birds, which may be carrying a disease to which the population is naive. Concerns about the risks of introducing disease into the wild by restocking with captive bred birds need to be set against a background of disease in the existing population. If a disease is already present, we may be less concerned about introducing that disease from captivity (Greenwood 1996).

There are disease risks associated with many management procedures, although these risks are often small. Fieldworkers may transmit parrot viruses on their clothes. Many of the problems can be minimized by good hygiene. Supplemental feeding stations need to be kept clean and only good quality food used. The spread of salmonellosis among British wild birds concentrated at garden feeding tables is well recognized (Wilson and Macdonald 1967). At the supplementary feeding stations used by free-living Echo Parakeets and Pink Pigeons, the hoppers have been designed to exclude most other species. A high incidence of trichomoniasis in young Pink Pigeons was believed to have been exacerbated by exotic doves drinking and feeding from the same hoppers (Greenwood 1996). The incidence of trichomoniasis decreased when the exotic doves were excluded.

Disease management can reduce mortality and some parasitic diseases can be treated in the field, especially at nest-sites. Tropical Nest Fly Passeromyia heterochaeta larvae feed on nestling Echo Parakeets and can be major source of mortality (Jones and Duffy 1993). This problem was eliminated by the addition of an insecticide dust (5% carbaryl) to the nest substrate at the beginning of the season, and every 2 weeks during the nestling period. Similarly, insecticide powder was applied to Black Robin nests to reduce the build-up of mites that, if unchecked, could cause brood desertion and mortality (Butler and Merton 1992). At Echo Parakeet nest cavities, the substrate was also treated with the abendazole to control fungal diseases such as aspergillosis.

12.3.4 Predator control

Predator control is a component of many bird restoration projects. When causes of predation are unknown, the approach should be protective, to minimize the possible impact of predators, and reactive, responding to any detected predation. The indiscriminate killing of even common predators is not recommended, as it may lead to unforeseen problems. An exception is when dealing with exotic predators known to be a problem elsewhere. In restoring native bird species on (p.279) islands, introduced rats Rattus spp., feral cats Felis catus, Small Indian Mongoose Herpestes auropunctatus, Stoat Mustela erminea, Mink M. vison, foxes Vulpes, and Alopex all are potential problem species (Merton 1978).

On mainland or continental areas, predator control is usually a localized or a short-term option where it is best focused around areas where the focal species is most vulnerable, that is, nest-sites, roost sites, feeding areas, supplementary feeding stations, and release sites. Long-term predator control over large areas is usually not sustainable. However, in New Zealand biologists are experimenting with managed areas of up to 6000 ha in which smaller core areas are intensively managed. These areas are termed “Mainland Islands.” Within these areas large herbivores are shot from helicopters and the exotic rats and Brushtail Possums Trichosurus vulpecula are controlled by the aerial distribution of toxic baits, and in the intensively managed areas trapping grids are set for exotic mammals including mustelids and feral cats. Mainland Islands have been successful in providing secure habitat for a range of native species and numbers of kiwi Apteryx spp. and Kokakos Callaeas cinerea have increased (Innes et al. 1999). A more sustainable long-term option is to eradicate exotic predators on islands, which can then be used as reintroduction sites for endangered bird species (see Translocations) or to enclose areas in predator proof fences.

Approaches available include close guarding, the provision of safe nest-sites, predator guards around nest trees, and the placement of supplemental feeding, and release sites in safe fenced locations. An advantage of close guarding is that it may reveal unknown predation problems. The first young Mauritius Kestrels released spent time on the ground, where they were susceptible to mongoose and cat predation, which explained losses of up to 25% of young at some sites. A close guarding and trapping program around some nest-sites and most release sites reduced the losses to these predators (Jones et al. 1991, 1995; Cade and Jones 1994).

The removal of introduced predators from islands may allow native birds that still exist to recover rapidly. On Little Barrier Island, New Zealand, fewer than 500 Stitchbirds Notiomystis cincta remained, but after the eradication of cats the population recovered within a few years to 3000 (Veitch 1985). Similarly on Raratonga in the Cook Islands, the endemic flycatcher Pomarea dimidiata declined to 29 birds in 1989, due primarily to nest predation by Black Rats Rattus rattus. Rat control with poison laid out on a grid system throughout the habitat, together with rat-proofing of nest-trees with predator guards, resulted in an increase in the population to 189 over the next 10 years (Bell and Merton 2002).

The Aleutian Canada Goose Branta canadensis leucopereia declined after Arctic Foxes and Red Foxes Vulpes vulpes were introduced to the islands where they bred. The breeding geese were reduced to just one fox-free island. (p.280) Foxes were removed from several islands and the goose population recovered to its former densities, helped by some reintroductions (Springer et al. 1978; Byrd et al. 1994).

The restoration of islands that can be used as refuges for endangered birds is a well-proven technique and is successful because harmful predators can be completely eradicated. On mainland areas, all that is usually possible is localized control or the fencing out of some problem species. Fencing technology is becoming increasingly sophisticated and the New Zealand “super fence” keeps out all mammals including rats and mice. The Karori Wildlife Sanctuary, Wellington has been surrounded by 8.6 km of fencing and threatened species that may formerly have occurred there such as the Little Spotted Kiwi Apteryx owenii are being re-introduced within the fenced area (Bell and Merton 2002; J. Mallam personal communication).

Predator control raises issues of ethics and welfare and should always be carried out to the highest standards. Although the science of predator control and eradication is well established, a great deal of experience is usually needed before trappers become efficient. Good trappers approach the subject with meticulous detail and a keen intuition and consequently may catch many more animals than a novice.

12.4 Intensive management of focal pairs

12.4.1 Close guarding and monitoring of nests

The main purposes of close guarding are to:

  • Monitor the progress of the focal pairs and to build a body of knowledge on the biology and behavior of the species.

  • Assess the suitability of the watched pair for possible clutch and brood manipulations.

  • Monitor the results and progress of any manipulations.

  • React to problems that threaten the pair or their nesting attempt (e.g. nest-site enhancement, supplemental feeding, control of parasites, predators, and competitors).

  • Rescue clutches and broods from failing nesting attempts, or if necessary hand-feed and re-hydrate ailing chicks.

In the most critically endangered species 24-h guarding and monitoring has sometimes been undertaken. Some are monitored by video systems (Kakapo project) or by teams of volunteers (California Condor, Pink Pigeon, Echo Parakeet projects), but there must be clear guidelines on procedures if the nest (p.281) shows signs of failing. Close guarding has been an important component in restoration programs for the Kakapo, Chatham Island Black Robin, Californian Condor, and Echo Parakeet. It has enhanced the productivity of focal pairs (e.g. Butler and Merton 1992; Jones and Duffy 1993; Jones et al. 1998; Merton et al. 1999; Snyder and Snyder 2000; Elliott et al. 2001).

12.4.2 Clutch and brood manipulations

The purposes of clutch and brood manipulations are to increase the productivity of focal pairs, providing the birds concerned will tolerate the intrusion. In most species of birds, the number of fertile eggs laid is considerably greater than the number of young that leave the nest. There are losses during incubation and rearing that can often be minimized by careful management, and the eggs or young can be harvested without increasing the overall loss.

In some species, if eggs are harvested one at a time or as whole clutches, replacement eggs, or clutches are laid, thereby increasing the number of viable eggs produced. The harvested eggs can then be hatched in other ways, and the young reared by hand or fostered in other nests. Brood manipulations increase or decrease the number of young in the nest, but can also involve cross-fostering, fostering, or supportive care to the chicks and parents.

Harvesting and rescuing eggs

These techniques have been applied to many species to minimize the loss of viable eggs. The Whooping Crane Grus americana normally lays two eggs but only one young usually survives. The “surplus” eggs were harvested for captive rearing. Of 50 eggs harvested from the wild, 41 (82%) hatched and 23 (56%) of the chicks were reared to at least 6 months old (Kepler 1978). These were used to establish a captive population to provide eggs and young for reintroduction.

An important egg harvesting study involved Peregrine Falcons in North America. The falcons had poor breeding success due to DDE contamination (from the insecticide DDT) that was causing the females to lay thin-shelled eggs. Most pairs failed because the incubating adults accidentally smashed the eggs, and this caused populations to decline. In one study, the hatch rate of thin-shelled eggs under the wild birds was only 7% (Craig et al. 1988). In a sample of 661 harvested eggs, 536 were apparently fertile and alive when harvested, 386 (72%) hatched, and 356 (92%) chicks were reared to fledging. The majority of these were released by fostering and hacking (Burnham et al. 1988; Walton and Thelander 1988). The latter is a procedure that allows young to fly naturally from an artificial nest-site, to which they can return for food until they have learned to hunt for themselves about a month later.

(p.282) Fostering of eggs

Eggs may be fostered to nests to add to those already there or to replace non-viable eggs. Fostered eggs should be at the same stage of development as the rest of the clutch.

Clutch augmentation is used with captive birds where pairs may incubate and hatch larger clutches than normal, but is limited by the number of eggs that the incubating bird can effectively cover. Wild birds on clutches larger than normal are likely to succeed in rearing larger broods only when natural food is not limiting or when extra food is provided.

Egg augmentation and replacement is an easy way to ensure that all nests in a population have the possibility to hatch young, and is an useful technique to introduce captive–produced eggs into a wild population.

Sequential egg removal

If an egg is removed soon after it is laid, the bird keeps laying further eggs in an attempt to complete a clutch, sometimes producing more eggs than the usual. This technique only works on birds that have an indeterminate clutch size. It is a technique most often used on captive birds, where the laying of eggs can be carefully monitored. Captive Sandhill Cranes Grus canadensis have exceptionally laid 18 and 19 eggs in succession, yet the normal clutch size does not exceed four. Single egg removal resulted in an average of 6.4 eggs per bird per year compared with 5.3 if the birds were “double clutched” (i.e. removal of a complete clutch to stimulate the laying of another). These egg removal studies did not have any marked effect upon egg viability (Ellis et al. 1996).

Multiple and double clutching

Many species of birds that normally produce only one clutch per season can lay a replacement clutch if the first nesting attempt fails, and some species can lay several clutches in a season. This ability to recycle can be exploited by removing the first clutch, and sometimes successive clutches, for artificial rearing (or fostering) and then leaving the pair with a final clutch to incubate and to rear themselves.

This technique was used for California Condors in the wild prior to the last birds being brought into captivity. Californian Condors lay single egg clutches and if they successfully rear a chick it is dependent on its parents for so long that they do not breed the following year; hence successful wild Condors can produce only a single independent young every other year. Between 1983 and 1986, 16 eggs were taken for artificial incubation from five different pairs. Thirteen (81%) of the eggs produced surviving chicks, far exceeding the 40–50% fledging success of wild (p.283) pairs. Of ten pairs whose first clutch was removed, six relayed; and following removal of these second clutches, three pairs went on to lay a third time in the one season. The condors were retained to establish the captive-breeding program for the species (Snyder and Hamber 1985; Snyder 1986; Toone and Wallace 1994; Snyder and Snyder 2000).

Double clutching of wild Peregrine Falcons became routine in the Western United States (see Harvesting and rescuing eggs) (e.g. Burnham et al. 1988, Walton and Thelander 1988). The clutch was typically removed 7–10 days after completion. The delay in removal was to allow some natural incubation, which increased the subsequent hatchability in incubators, compared to eggs in incubators throughout. In one sample of 13 removed first clutches, all pairs laid a second clutch, usually after about 12 days. Second clutches were sometimes smaller and averaged 3.2 eggs, compared to 3.5 eggs in first clutches (Craig et al. 1988).

Double clutching was tried on Echo Parakeets, but with poor success. First clutches were removed, or lost, from wild pairs on 18 occasions, and in twelve (67%) of these a second clutch was laid. The second clutch was started 19–21 days (once about 30 days) after the loss of the first clutch. It was difficult to predict in Echo Parakeets if a pair would renest, and repeat nesting attempts were not as successful as first ones. Only 23% of eggs from second clutches resulted in fledged young (Jones and Duffy 1993; Jones et al. 1998). In view of this poor success, double clutching was stopped.

Many species respond to loss of a clutch by moving to another nest-site, so clutch removal has been used to move Peregrine Falcons from unsuitable nest-sites to secure ones (Craig et al. 1988) and to move Mauritius Kestrels from cavities that were accessible to predators to predator-proof nest-boxes.

Because egg quality often declines in replacement clutches, there are tradeoffs in management that have to be considered. A protocol for the harvesting of eggs from wild pairs of Mauritius Kestrels was developed, in which no pair was made to lay more than one extra clutch in a season. Harvested eggs of many species of wild birds have a better hatchability in artificial incubators if they have received some natural incubation, yet the birds recycle more readily if the eggs are harvested soon after the first clutch has been laid. In Mauritius Kestrels, the eggs were harvested about 5–7 days after clutch completion. Following the removal of the clutch, Mauritius Kestrels would usually move nest-site, so alternative nest-boxes were provided. First time breeders were left with their first clutch and not encouraged to lay additional eggs. It was considered important that young birds should rear young if they were to become good breeders in future years (Jones et al. 1991). Similar protocols have been applied to Peregrine Falcons (Walton and Thelander 1988).

(p.284) Fostering

Three main types of fostering can be distinguished:

  • Augmentation. The addition of young, thus increasing the size of the brood.

  • Replacement. The replacement of a clutch of eggs with a brood of young, or the replacement of one brood with another.

  • Swapping. The swapping of young between broods, so that all the young are about the same size, thus reducing the risk of mortality.

Fostering has been widely practiced in captivity in a range of species from many different orders. Work on wild birds has been limited, and the most detailed and successful studies have involved birds of prey.

In general, the more experienced the pair, the more liberties can be taken. Some pairs are poor at rearing and can never be trusted with their own or fostered young. The young to be fostered should not have developed fear reactions or they may refuse to accept food from the adults. In species that produce altricial young, fear reactions do not usually develop until the second half of the nestling period. Fostering attempts with species that produce precocial young are usually done as eggs since the young form attachments to their parents soon after hatching.

Augmentation fostering.

The candidates for augmentation fostering are usually birds with a smaller than normal broods. The fostered young should be close to the age and size of the young that the adults are rearing.

The enlargement of normal brood size by adding extra chicks to the nests of altricial species has given variable results. In 11 out of 40 brood enlargement experiments reviewed by Dijkstra et al. (1990), enlarged broods suffered greater mortality and yielded fewer fledglings than control broods, suggesting that in these cases food was limiting. In the remaining 29 experiments, the enlarged broods produced more fledglings, on average, than control ones, showing that many species were able to raise larger than normal broods. If birds are to be given extra young, extra food provision is a good precaution.

Replacement fostering.

The replacement of whole clutches of eggs with young is usually applied to birds that have been incubating non-viable eggs or whose eggs are needed for other purposes. The young do better if they are several days old and hence are stronger and easier to feed than newly hatched chicks. Large falcons accept young up to about 3 weeks old (Fyfe et al. 1978). In Echo Parakeets the optimal age for fostering is 4–7 days, although experienced females will accept and rear younger or older chicks.

(p.285) Experience with wild Mauritius Kestrels and Echo Parakeets has shown that, if birds fail in breeding, but are going to be required to foster young later, then they can be given dummy eggs, even for up to 5 days after the young have hatched. They will incubate these for up to 5 days and when given the foster young will look after them.

Swapping.

In some species, such as raptors and parrots, where hatching is asynchronous, the smaller young have poorer survival. The swapping of young between broods, so that all in each brood are about the same size, can enhance the survival of the compromised young and increase brood size at fledging. This has worked with several species including Kakapo, Echo Parakeet, Mauritius Kestrel, Pink Pigeon, and Spanish Imperial Eagle Aquila adalberti (Meyburg 1978).

Cross-fostering of eggs and young.

Cross-fostering the young (or eggs) from one species to another has been tried in many taxa. Usually a common species is used to rear the young of a rarer species, freeing up the rarer species to lay additional clutches. Sometimes, however, the young of a common species have been fostered to a rarer species to test parental abilities and to provide rearing experience before a fostering attempt with a conspecific.

For centuries strains of domestic chickens have been used to incubate the eggs and rear the chicks of captive game birds and waterfowl. Domestic Bengalese Finches Lonchuria striata have been used to rear rarer estrildid finches, especially Gouldian Finches Chloebia gouldiae. But most of the conservation-orientated cross-fostering studies on wild birds have involved diurnal birds of prey and the Chatham Island Black Robin, where cross-fostering has been attempted using a common species to rear the young of a rarer species. Olendorff et al. (1980) and Barclay (1987) review cross-fostering studies in raptors involving 12 different species.

Intra-generic cross-fostering.

McIlhenny (1934) pioneered cross-fostering as a successful conservation technique on wild birds. Snowy Egret Egretta thula eggs were harvested and cross-fostered to the nests of the commoner Little Blue Herons E. caerulea and Tricolored Herons E. tricolor. The Snowy Egrets recycled and were left to incubate their second clutches and rear the young. The cross-fostering was successful and the Snowy Egret population rapidly increased.

Subsequently the cross-fostering of wild birds was attempted in ethological studies. Schutz (1940 quoted by Cade 1978) placed the eggs from a tree-nesting colony of Common Gulls Larus canus in the nests of Black-headed Gulls L. ridibundus among reeds. On reaching sexual maturity, the Common Gulls returned to their hatching and rearing location and formed a small colony within the Black-headed Gull colony. The Common Gulls adopted a new breeding (p.286) location and apparently paired preferentially with their own species rather than with Black-headed Gulls.

Harris (1970) swapped the eggs of the Lesser Black-backed Gulls Larus fuscus with Herring Gulls Larus argentatus on Skokholm Island, Wales. Some 496 Lesser Black-backed Gull eggs were placed in the nests of Herring Gulls and 389 Herring Gull eggs were placed in the nests of Lesser Black-backed Gulls. Cross-fostered gulls were subsequently found breeding on Skokholm and, of these, 71 were in mixed species pairs and 44 were breeding with their own species. Harris found that cross-fostered females usually mated with the males of their foster parent while the males mated with either species.

In an attempt to reintroduce Peregrine Falcons into their former range, young were fostered in several areas into the nests of Prairie Falcon Falco mexicanus. In California 113 nestling Peregrine Falcons were fostered into nests of wild Prairie Falcons, and all or most fledged. About ten of these cross-fostered Peregrines were later found breeding normally in the wild and none was seen mated to a Prairie Falcon (Walton and Thelander 1988; Cade and Temple 1995).

In the Mauritius Kestrel, inexperienced wild pairs were, on four occasions, given pipping eggs of Common Kestrels Falco tinnunculus to gain experience of hatching and rearing. One pair proved competent enough for the Common Kestrels to be replaced with Mauritius Kestrels (Jones et al. 1992). Similarly, Chatham Island Tits Petroica macrocephala were fostered under the rarer Chatham Islanc Black Robins to give the robins rearing experience (Butler and Merton 1992).

The cross-fostering of Chatham Island Black Robins has been the most successful use of this technique for the conservation of a critically endangered species. Black Robin eggs and young were cross-fostered under Chatham Island Tits and Chatham Island Warblers Gerygone albofrontata, a procedure which encouraged Robin pairs to lay replacement clutches. Although the warblers hatched the eggs and reared the young robins successfully for the first week, they could not bring sufficient food to rear them beyond 10 days old. Subsequently, if warblers were used as foster parents, the young were moved back to robins after a week. The tits could rear the Black Robins successfully to fledging, but these young imprinted to, and attempted to breed with tits. This was overcome by: (1) swapping the cross-fostered young back to robins before fledging so that they developed the appropriate species fixation; and (2) translocating robins that fledged under tits to an island lacking tits so that the robins had no option but to breed with each other, which they did with some initial reluctance. Of 180 black robin eggs incubated by tits, 156 (87%) hatched-a figure comparable to that from eggs incubated entirely byrobins (Butler and Merton 1992).

(p.287) Cross-fostering should proceed with care because of the very real problems of sexual imprinting to the foster species (Immelman 1972). Due to the taxonomic closeness of species within the same genus there is the possibility that they would produce fertile hybrids. For example, Scarlet Ibises Eodocimus ruber were introduced to Florida by cross-fostering the eggs to White Ibises E. albus. This procedure resulted in considerable hybridization, producing “pink” ibises (Long 1981).

Inter-generic cross-fostering.

After a series of cross-fostering experiments in captivity, Fyfe et al. (1978) experimented by placing broods of Prairie Falcons under three species of Buteo hawks. This was done to test the suitability of these different Buteo species as foster parents, but also to see if the procedure could be used to extend the Prairie Falcon's distribution. Two paris of Ferruginous Hawks Buteo regalis raised four out of five young, three pairs of Red-tailed Hawks B. jamaicensis raised ten out of eleven young and a pair of Swainson's Hawks B. swainsoni raised four out of five young in a single brood. Subsequently three pairs of Prairie Falcons were found breeding near to the cross-fostering sites but outside of the natural range of Prairie Falcons; they were assumed to have been the young from the cross-fostering experiments. One pair even nested for two seasons in an old Buteo nest, the first time this behavior had been recorded in prairie Falcons. Clearly this trial, although modest in terms of sample size, demonstrates the potential of the technique. Similarly, in Germany Common Buzzards Buteo buteo, Goshawks Accipiter gentilis, and Common Kestrels nesting in trees have been used to rear young Peregrine Falcons in an attempt to re-establish a tree nesting tradition in the latter species (Saar 1988). Several pairs of Peregrine Falcons have subsequently nested in trees in the area concerned (Cade 2000).

Where possible, cross-fostering should be of whole broods so that the siblings can socialize with each other. Where single young are raised by foster parents of another species, then the only possibilities of early socializing and sexual imprinting are with the foster parents, as indeed happened when Whooping Cranes were fostered under Sandhill Cranes Grus canadensis (Ellis et al. 1996). Cross-fostering has worked well in some inter-generic attempts, where hybridization between the species was highly unlikely, as demonstrated by the successful rearing of young falcons by Buteo and Accipiter hawks.

There are clear behavioral constraints on which species will tolerate the young of another species. In small passerines, neither domestic Bengalese Finches (Estrildidae) nor domestic Canaries (Fringillidae) reared the young of Madagascar Fodies Foudia madagascariensis (Ploceidae) even though they incubated and hatched the eggs. Neither species responded to the begging cries and gaping of the young fodies. The Bengalese Finches did, however, rear the young of the (p.288) congeneric Spice Fince Lonchura punctulata even if they were not themselves either incubating or rearing young at the time (C.G. Jones, unpublished).

Chick rescue

Some species of birds hatch more young than they successfully rear, and in any restoration project opportunites may arise to rescue failing chicks. Rescued chicks are likely to be under-weight and dehydrated, with reduced survival chances, but some survive for release to the wild.

The young of several species of eagles engage in siblicide or “cainism,” where one chick may kill its siblings. Studies on Lesser Spotted Eagles Aquila pomarina, Spanish Imperial Eagles and Madagascar Fish Eagles Haliaeetus albicilla have all demonstrated that the productivity of these eagles can be increased by removing the weakest chick for hand-rearing, fostering or cross-fostering (Meyburg 1978; Watson et al. 1996; Cade 2000). This approach has potential to boost the productivity of rare eagles.

Rescuing chicks that are not growing well has been a valuable technique in the management of the California Condor (Snyder and Snyder 2000) and Echo Parakeet. Wild parakeets lay clutches of 2–4 eggs but usually only rear one chick, sometimes two, aparently because insufficient food is available. To avoid this loss, wild parakeets are allowed to hatch their eggs and keep the young for the first 5–8 days. Young were then removed and either hand reared or given to foster pairs that had failed to hatch their own young. Of 38 chicks rescued when starving, 29 (78%) fledged, while of 14 chicks removed earlier, all subsequently fledged.

Supportive care of young birds in the nest

Providing supportive care to young birds in the nest during periods of temporary food shortage, when the adults are having difficulty feeding them, may improve their survival chances. Young birds fostered under inexperienced adults, in replacement of a clutch of eggs, may need some hand-feeding while the parents learn how to feed them adequately. During inclement weather, when adults have difficulty foraging, it has sometimes proven necessary to feed and re-hydrate young Mauritius Kestrels and Echo Parakeets in the nest to help them through a brief period of food shortage. However, it is usually more efficient to feed the adults, if they will accept supplemental food, and let them pass it on to the young.

12.5 Reintroduction and translocations

12.5.1 Reintroduction

Reintroduction is usually defined as the release of captive-breed or captive-reared birds into an area which was once part of their range but from which they have (p.289) become extirpated (IUCN 1998), but can also include the addition of individuals to an existing population. This latter category of reintroductions is often treated separately as re-enforcement or supplementation (IUCN 1998), but since both types of reintroduction are often used in the same project, they are here treated together.

Reintroductions have received a great deal of attention due to their high profile nature (Fyfe 1978; Cade 2000). The reintroduction of some species works well (birds of prey), and others have proven problematic (parrots, hornbills, and some passerines). Successes are becoming more frequent, as we learn more about the needs of different species. There are several different release techniques, of which fostering and cross-fostering of eggs and young have already been described. Other release processes can be divided into hard or soft releases. The hard release (also termed abrupt release) is when the bird is released without any preliminary conditioning to the area and is not given any support thereafter, on the assumption that it will be able to look after itself. Many early reintroductions were of this type and were characterized by a high failure rate. As a rule, hard releases are best avoided.

In soft release (also called gentle release), the birds are habituated to the area before release and are provided with some form of support during the release process. Usually the birds are provisioned after release with food and water, so that they can become independent of human care gradually. Soft releases are more successful than hard-releases. For example, post release survival to 1 year was 12% of 51 Sandhill Cranes that were hard-released, and 68% of 238 cranes that were soft-released (Nagendran et al. 1996).

The process of a soft release falls into three stages: (1) pre-release training and conditioning; (2) the release process; and (3) post-release support. Birds intended for release have to be correctly socialized, with due care taken to ensure that the stimuli during the early learning stages are appropriate. For most releases, parent reared, or foster raised birds are to be desired because they will have experienced normal imprinting and socialization. If hand-raised birds are being used, it is important that they are raised with siblings to ensure socialization with conspecifics or, if they are being raised alone, that they are fed with the aid of puppet that mimics the adult so that they young birds imprint upon an appropriate image (Wallace 2000). Puppet rearing has been used with Californian Condors, and Takahe Porphyrio mantelli. For cranes, the rearer wears a full body crane suit. Attention also needs to be given to early learning of nest-site characteristics, and all individuals should be provided with opportunities to develop physical and survival skills (Wallace 2000).

Birds of prey are usually released using a soft release technique called “hacking” (Sherrod et al. 1981). The birds are placed in an artificial nest-site once they are homeothermic and are old enough to feed themselves from provisioned food. (p.290) The birds fledge from the artificial nest-site at the usual fledging age and develop their flying and hunting skills gradually at ages comparable to wild-reared birds. During this learning period, food is provided on or near the nest until it is no longer taken.

The hacking technique is not suitable for some other groups of birds that are incapable of feeding themselves from provisioned food until after fledging. Hence, they are usually kept in captivity until they have been fully weaned, and released.

Released birds are unlikely to do as well as young reared in the wild. There are exceptions, however, for survival of released birds of prey is very high and in Mauritius Kestrels is comparable to that of wild fledged birds. Survival in reintroduced captive-reared Takahe was also equal to that of wild reared birds (Maxwell and Jamieson 1997), as was that of Pink Pigeons, although for the pigeons additional food was provided and predators were controlled (Swinnerton 2001).

For most species, the earlier in the post-fledging period they can be released, the better their subsequent survival. In the Pink Pigeon, 68% of 196 birds released before reaching 150 days survived for at least a year post-release, compared to 56% of 52 birds released at a greater age (Swinnerton 2001). Griffon Vultures Gyps fulvus were unusual in that birds released as adults survived better than those released as juveniles (Sarrazin et al. 1994). In this social species, the released vultures joined previously released birds from which they presumably learned their survival skills. These vultures were artificially provisioned with food (Terrase et al. 1994). In all social species, releases seemed more successful if there were other birds from previous releases nearby from which newcomers could learn.

Once the birds have been free for a designated period, food and water are gradually reduced and the birds are left to fend for themselves. The degree of post-release care is variable between projects and some also provide close guarding, individual monitoring, veterinary backup, and predator control. Some species need to be supported long-term following release, especially if the release environment is sub-optimal in some way. Some social species, such as parrots and hornbills may, in some cases, have to be supported for at least a generation post-release, especially if there are no wild or previously released conspecifics established in the area to pass on appropriate social and survival skills.

12.5.2 Translocations

Translocations involve the movement of wild birds from one area of habitat to another. The most appropriate birds to move are usually juveniles, using the same release and post-release management as for captive-raised birds. Adults are more (p.291) likely to have the necessary survival skills, but are also more likely to leave the release are and return to their site of origin. An early successful translocation was of 3100 Snowy Egrets that were moved from Louisiana to Florida in the United States in 1909. They were held captive for several months and then released. These birds helped to re-establish the species in Florida (McIlhenny 1934).

Translocations that have worked well include island endemics moved onto other islands from which introduced mammalian predators have been eradicated. The New Zealanders are the pioneers in this type of management and have successfully translocated the Eastern Weka Gallirallus australis, North Island Weka G. a. greyi, the two races of saddleback Philesturnus carunculatus (Merton 1975), Chatham Islands Snipe Coenocorypha aucklandica pusilla, Black Robin, Brown Teal Anas aucklandica chorotis, Kakapo, Kokako Callaeus cineria, North Island Brown Kiwi Apteryx mantelli and Little Spotted Kiwi, Stitchbird Notiomystis cincta and Takahe (Bell and Merton 2001). In the Seychelles, the Magpie Robin Copsychus sechellarum (Watson et al. 1992) and Seychelles Brush Warbler Acrocephalus sechellensis (Komdeur 1994) have been successfully moved to other islands. In western Australia, the Noisy Scrub-bird Atrichornis clamosus has been succcessfully translocated from its last natural stronghold in the southwest of the state to a number of mainland sites and one island (Bell and Merton 2002).

Some of these translocations have probably ensured the survival of the species involved. In New Zealand, many of the endemic birds cannot coexist with the introduced predators that now exist on the mainland, and the two races of saddleback, Eastern Weka and Kakapo all now exist on islands beyond their natural range (Bell and Merton 2002).

12.6 Supportive management for bird restoration projects

12.6.1 Role of captive facilities

Captive breeding projects that are established near to wild populations have the advantage that the movements of birds and eggs from the wild to captivity and vice versa is relatively easy. In addition, skilled personnel can be readily moved from the captive-breeding program into the field for the application of avicultural techniques to the wild birds, while field researchers can be used in the captive-breeding program.

Captive breeding has played an important role in the restoration of several critically endangered species and populations. The restoration of Peregrine Falcon populations in North America, Sweden, Germany, and elsewhere relied almost exclusively on captive-produced birds (Cade et al. 1988), as did the (p.292) restoration of the Hawaiian Goose Branta sandvicensis (Black and Banko 1994), Whooping Crane (Ellis et al. 1996), and Pink Pigeon (Jones et al. 1992). However, captive breeding is not essential if the free-living populations can be closely managed, as in the Kakapo and Black Robin (Bell and Merton 2002). In the Kakapo, harvested and rescued eggs and young were brought into captivity for artificial incubation and hand-rearing, with subsequent reintroduction to the wild. Avian pediatric medicine and care are proving to be important for most intensively managed bird populations.

Captive-breeding facilities have a role in the development of techniques, and training personnel for use in future bird restoration projects. Some of the intensive management techniques can best be learnt on captive birds. We need to know which clutch and brood manipulations work for which species, and what are the costs and benefits of each technique in terms of lifetime reproductive output.

12.6.2 Model or surrogate species

Closely related surrogate species, which similar ecology to the target species may serve a number of functions.

  1. 1. Development of techniques before being applied to the rarer species. these may include captive breeding, artificial incubation, hand-rearing, and release techniques. For example, on Mauritius, Ring-necked Parakeets Psittacula krameri were released to develop techniques for the Echo Parakeet releases, and in California, Andean Condors Vultur gryphus were released (and later recaptured) to test release techniques for Californian Condors (Wallace and Temple 1987).

  2. 2. Staff training. Staff can learn handling and management techniques on a commoner species before they are applied to the focal species.

  3. 3. Foster parents for cross-fostering in captivity (e.g. Ring-necked Parakeets for Echo Parakeets and Barbary Doves Streptopelia risoria for Pink Pigeons).

The use of surrogate species, both in the wild and captivity, has been extensive in North America. For example, the Patuxent Wildlife Research Center worked first on Sandhill Cranes in order to develop captive breeding and management techniques applicable to the rarer Whooping Crane (Kepler 1978). Similarly Prairie Falcons were experimentally manipulated in the wild and kept in captivity by both The Peregrine Fund and the Canadian Wildlife Service to train personnel and to develop management techniques for application to the rarer Peregrine (Fyfe 1976).

12.6.3 Artificial incubation and hand-rearing

Avian pediatrics has primarily been developed in captive-breeding facilities and is most advanced in groups of birds of greaters commercial value: ratites, raptors, (p.293) waterfowl, parrots, and passerines, although the number of experienced personnel is small.

Artificial incubation and hand-rearing provide supportive captive management for clutch and brood manipulations. In established projects with experienced personnel and good facilities, hatchability of fertile eggs is likely to reach 80%, and rearing success 90% in many groups of birds.

12.7 Integrated management

Some of the most marked recoveries of critically endangered species entailed a range of management practices, some of which were applied simultaneously. In Table 12.1 the management procedures that were applied to the Mauritius Kestrel, Pink Pigeon, Echo Parakeet, and Black Robin are all listed. All these species recovered from tiny populations and management involved the whole population.

The Mauritius Kestrel recovered from a wild population of four known birds in 1974 to between 600 and 800 in early 2003; the Pink Pigeon from 10 wild birds in 1990 to about 350 free-living birds in 2003, the Echo Parakeet from 8 to 11 known birds in 1987 to 175-200 free-living birds in 2003; and the Black Robin from 5 birds in 1980 to about 300 in 2001. In all these species, the genetic variance in the tiny remnant populations must have been small, yet they recovered to give large free-living populations (Groombridge et al. 2000). For some of these, however, continued management may be necessary in the future.

12.8 Discussion

In effect, species are rare or declining because of poor productivity and/or reduced survival, whatever the ultimate cause. The application of intensive management techniques to small and declining populations offers high chances of a rapid increase. However, because these techniques are intensive they are less appropriate for use on widespread populations, and many of the most successful examples are from relatively tame island species. Moreover, they are unlikely to succeed long-term unless the ultimate causes of poor status are addressed, whether these are loss of habitat and food supply, predation from people or introduced predators, new diseases or other factors.

The application of techniques, such as fostering, and cross fostering of eggs and young, works best with species that have high nest success (e.g. raptors, cranes, and parrots). With many other species the levels of nest failure in the wild are too high to justify the investment of time and energy. A broader approach to population management is often more appropriate, including, for example, (p.294)

Table 12.1 The management techniques used in the restoration of four Critically End angered island endemics

Management technique

Mauritius Kestrel

Pink pigeon

Echo parakeet

Block Robin

Supplemental feeding of free-living adulds

*

**

**

**

Supplemental feeding of released birds

**

**

**

N/a

Supplemental feeding of depented young

*

*

**

Nest site enhancement

**

**

**

Provision of artificial nest sites

**

*

**

**

Egg manipulations

**

**

**

**

Fostering of young

**

*

**

**

Cross fostering of young

*

*

*

**

Nest guarding

**

**

**

**

Rescue of eggs and young from failing nests

**

**

**

**

Captive breeding

**

**

**

N/a

Release of captive bred/reared young

**

**

**

N/a

Translocation of free-living birds

*

**

**

Predator control in breeding areas

*

**

**

Predator control at supplemental feeding sites

**

**

Predator control at release sites

**

**

**

N/a

Predator exclution (fencing)

**

control of nest competitors

*

**

**

Discase control

*

**

**

**

control of disease vectors

*

Genitic management

**

**

**

**

Habitat restoration

**

**

**

* = Management technique used experimentally or on small scale and did not have a significant effect on the population.

** = Technique used extensively and is thought to, or known to have had a beneficial effect on the population.

N/a = Not applicable.

For details of these techniques and their application see Cade and Jones (1994), and Duffy (1993), jones et al. (1991, 1992, 1995, 1999),Jones and Hartley (1995) and Jones and Swinnerton (1997), Butler and Merton (1992).

(p.295) Predator control, supplemental feeding, nest-site management, together with reintroductions, and translocations.

To be effective, endangered species management has to be focused. It is possible only with teams of dedicated personnel, long-term commitment from supporting organizations, and access to skilled technicians.

Programs for the four species considered in Table 12.1 followed the steps discussed in Section 12.2. From the first conservation oriented field studies (Stage 1) to the start of intensive management (Stage 3) took between 8 years for the Black Robin and 20 years for the Echo parakeet. The intensive management stage took about 9 years for the Black Robin (Butler and Merton 1992), 10 years for the Mauritius Kesterel (Jones et al. 1995) and 10 years for the Pink Pigeon (Swinnerton 2001). The Echo Parakeet is still at Stage Three and is likely to be intensively managed for a total of 10–12 years. Hence, these data suggest that it can take from 17 to 30 years to restore a population from being Critically Endangered (and poorly studied) through to the stage at which it requires minimal further management. For large, long lived, slow breeding species (Kakapo, Californian Condor, Whooping Crane), this time is likely to be much longer.

As we learn more about bird management, it should be possible to compress States 1 and 2 to a few years. But it seems likely that the restoration of Critically Endangered bird populations will always be a relatively long-term commitment. It is also likely that, with the increasing loss and degradation of habitat, it will be necessary to manage some bird populations in perpetuity if they are to survive, providing safe nest-sites, and food and managing predators.

A basic premise of intensive management is that it address proximate rather than ultimate causes of endangerment (Temple 1978). A population may be rescued in the short term by intensive management but long-term survival is best guaranteed if this management is coupled with efforts to address the ultimate problems, often related to habitat loss or degradation (Cade and Temple 1995). Intensive management often helps to clarify which environmental problems are causing the species' rarity, and it is recovery work that may drive the efforts to address the ultimate problems.

On Mauritius, species restoration has driven habitat restorations. The political will to establish a National park arose as a direct result of restoration work on the endemic birds. Similarly, in New Zealand the restoration of many offshore islands has been done primarily to provide refuges for endangered birds.

Most critically endangered species would probably respond favorably to intensive management. Gurney's Pitta Pitta gurneyi had a known population of nine pairs in 1997 due primarily to habitat destruction (Stattersfield and Capper 2000). In June 2003 a survey revealed 31 birds of which 18 were males and an estimate of (p.296) 15–20 pairs (A. Owen personal communication). The species was also rediscovered at four sites in neighboring Myanmar where there were 10–12 pairs at one site, although none of these sites are officially protected. While there may be possibilities for habitat restoration or to establish additional populations, in the long-term the immediate concern is to improve productivity and to use “surplus” birds derived from clutch and brood manipulations, to establish managed and or captive populations. Captive pitas of other species readily lay repeat clutches and there is every likelihood that Gurney's Pitta would also do so. The clutch size is usually 3–4, but nest predation is frequent and nest success low, with brood size at fledging usually being one or sometimes two (Lambert and Woodcock 1996). With a high level of natural egg and chick mortality, this productivity would be improved by close guarding and the application of clutch and brood manipulations.

Released animals can be managed at liberty and this offer opportunities for re-establishing species that may otherwise be difficult to reintroduce. The Spix Macaw Cyanopsitta spixii is now extinct in the wild, but there are about 70 birds in captivity. It has been proposed to release captive bred birds but this may prove difficult, because large parrots may rely to some extent on cultural transmission of information across generations, and with no wild birds left such learning will not be possible. Intensive management of released birds, with close guarding and provision of food, nest-sites and predator control may help their survival and breeding success. It is likely that the high level of management that would be necessary to establish Spix Macaws at liberty could be reduced as successive generations become more self sufficient.

Management of released birds also allows the possibility of maintaining populations in areas that would normally be unsuitable or marginal. This approach has resulted in the establishment of populations of formerly critically endangered species (Pink Pigeon, Hawaiian Goose) or species extinct in the wild (Kakapo). It opens up possibilities for the management at liberty of species that haves critically endangered wild populations but have thriving captive populations (Northern Bald Ibis and the Bali Mynah Leucopsar rothschildi). Managed reintroduced populations of Bali Mynah and Northern Bald Ibis would provide data that could help in understanding the needs of the wild birds and increase the public profile of these species. In the long-term, having free-living birds with a low level of management would be more desirable than having the species existing only in captivity.

Applied population management offers potent possibilities for the restoration of most species of endangered birds, but is time consuming and may be expensive.

Acknowledgements

I thank the staff of the Mauritian Wildlife Foundation for help with this chapter in particular Kirsty Swinnerton, Jason Mallam, Steve Cranewell, Tom Bodie, and (p.297) Nancy Bunbury. Drs Andrew Greenwood and Diana Bell commented and greatly improved the manuscript.

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