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Providing evidence to improve practice

Individual study: A review of ex situ and in situ conservation techniques for bald eagles Haliaeetus leucocephalus at a wildlife research centre in Maryland, USA and across the eastern USA

Published source details

Wiemeyer S.N. (1981) Captive propagation of bald eagles at Patuxent Wildlife Research Center and introductions into the wild. Raptor Research, 15, 68-82


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Foster eggs or chicks of raptors with wild conspecifics Bird Conservation

A replicated study in the eastern USA in 1977-80 (Wiemeyer 1981) found that, of 12 captive bred bald eagle Haliaeetus leucocephalus nestlings (ten hand-reared and two parent-reared) fostered to wild nests when they were 2.5-5 weeks old, 11 were accepted by the foster parents. The remaining nestling was killed by a foster parent shortly after being introduced to the nest. Wild nests all had either eggs (including dummy eggs designed to induce continued incubation) or nestlings, which sometimes remained in the nest and were sometimes transferred to other wild nests. All foster pairs had histories of reproductive failure. In addition, in 1978-9, six captive-produced eggs were transferred to wild nests in the Chesapeake Bay area of Virginia and Delaware. Only one of these hatched and the eaglet was successfully raised and fledged. It is not known whether the other eggs were fertile, but the authors suggest that they may have been chilled after foster parents took a long time to return to the nest after the introduction of the new eggs. A further two eaglets were removed from the wild as eggs, hand-reared (described in ‘Artificially incubate and hand-rear birds in captivity’) and returned to more successful wild nests. Both eaglets were seen in advanced stages of development and were presumed to have fledged. This study also describes several ex situ interventions, discussed in ‘Use captive breeding to increase or maintain populations’, ‘Use artificial insemination in captive breeding’ and ‘Release captive-bred individuals’.

 

Use artificial insemination in captive breeding Bird Conservation

A small study in a breeding centre in Maryland, USA, in 1980 (Wiemeyer 1981) found that an artificially inseminated, wild-bred, female bald eagle Haliaeetus leucocephalus laid two eggs, but both were infertile. The sperm was taken from one wild-bred male and one captive-bred male and mixed and the female was inseminated within an hour. The authors suggested that repeated inseminations would have been preferable, but that the disturbance caused by capturing and inseminating the female risked disturbing other breeding birds nearby. This study is also discussed in ‘Use captive breeding to increase or maintain populations’, ‘Release captive-bred individuals’ and ‘Foster birds with wild conspecifics’.

 

Artificially incubate and hand-rear raptors in captivity Bird Conservation

A replicated study in a breeding centre in Maryland, USA, in 1978-80 (Wiemeyer 1981) found that, of 16 bald eagle Haliaeetus leucocephalus eggs removed from captive breeding pairs (in a total of 11 clutches) and artificially incubated, 11 (69%) hatched. All 11 chicks were successfully raised until they were transferred to foster nests (see ‘Foster birds with wild conspecifics’). They were incubated at 56% humidity under one 37.6oC (‘dry’) bulb and one 30oC (‘wet’) bulb and turned every two hours. Once hatched, the chicks were fed on chopped meat and fish and provided with vitamin and calcium carbonate supplements. A further five eggs were removed from eagle nests with poor reproductive histories and artificially incubated. Three of these hatched and two of the eaglets survived hand-rearing to be fostered by more successful wild pairs. This programme is also discussed in ‘Use artificial insemination in captive breeding’, ‘Use captive breeding to increase or maintain populations’ and ‘Release captive-bred individuals’.

 

Use captive breeding to increase or maintain populations of raptors Bird Conservation

A small study at a wildlife research centre in Maryland, USA (Wiemeyer 1981), found that, between 1976 and 1980, between one and five pairs of captive bald eagles, Haliaeetus leucocephalus, incubated 31 eggs. Of these, 15 were fertile (48%) and 14 hatched (45% of all, 93% of fertile eggs). The one failure was possibly due to a wild bird disturbing the pair and causing them to cease incubation. The main cause of infertility appeared to be lack of matings between pairs, with each pair producing infertile clutches the first year they were paired. Clutches averaged 2.5 eggs for first clutches and 1.9 for second. This study is also discussed in ‘Use artificial insemination in captive breeding’, ‘Artificially incubate and hand-rear birds in captivity’, ‘Foster birds with wild conspecifics’ and ‘Release captive-bred individuals’.

 

Release captive-bred individuals into the wild to restore or augment wild populations of raptors Bird Conservation

A replicated study of bald eagle Haliaeetus leucocephalus reintroductions from a breeding centre in Maryland, USA (Wiemeyer 1981), found that all eleven captive-bred, parent-reared birds hacked at two sites in New York and Georgia, USA, successfully reached independence. This study is also discussed in ‘Use captive breeding to increase or maintain populations’, ‘Use artificial insemination in captive breeding’ and ‘Foster birds with wild conspecifics’.