Action: Use techniques to increase the survival of species after capture
- A small controlled study from the USA found that providing dark, quiet environments with readily-available food and water increased the survival of small birds after capture and increased the probability that they would accept captivity.
- A study from Hawaii found that keeping birds warm in a ‘mock’ translocation in Hawaii increased survival, although all birds suffered some loss of condition.
Translocations can be a stressful and potentially dangerous procedure, with birds being confined for potentially long periods of time after being captured from the wild. Techniques to maximise survival may therefore be an important part of ensuring the overall success of translocations. In addition, ensuring higher survival can help to reduce the impact of translocations on source populations by requiring fewer individuals to be taken.
Supporting evidence from individual studies
A small controlled study over the summers of 1986-1988 tested two transportation methods (prior to reintroduction attempts) from Michigan to Ohio, USA (Bocetti 1994) and found that Nashville warblers Vermivora ruficapilla were more likely to survive using a modified technique that provided dark, quiet environments, prompter delivery of food and water and reduced handling time. When the standard technique for introducing warblers to captivity was used, 79% of warblers appeared to adapt to the captive environment and five birds died. When the new technique was used, 88% and 96% warblers (1987 and 1988 respectively) adapted, significantly more than when using the standard technique. A total of 188 trips (612 km one-way) were made without fatality.
A small controlled study on Hawaii in December 1996 evaluated the effects of translocation on common amakihi Hemignathus virens and Japanese white-eyes Zosterops japonicas (Work et al. 1999). Birds kept overnight without thermal support had significantly higher mortality rates (4/10 birds in both species) than those provided with thermal support (0/10 common amakihi and 1/10 Japanese white-eyes), and birds that lost the most weight had the highest mortality. Birds were captured, transported by car for four hours and kept in captivity for 48 hours before release. All birds suffered weight loss, and fat and protein store depletion, with all deaths occurring within the first 24 hours following capture, regardless of whether the birds were quarantined and then transported or transported and then quarantined. Bird age, capture weight, or fat score did not affect survival rates.
- Bocetti C.I. (1994) Techniques for prolonged confinement and transport of small insectivorous passerines. Journal of Field Ornithology, 65, 232-236
- Work T.M., Massey J.G., Johnson L., Dougill S. & Banko P.C. (1999) Survival and physiologic responses of common amakihi and Japanese white-eyes during simulated translocation. The Condor, 101, 21-27