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Behavioural and corticosterone responses to capture and confinement of wild blackbirds ( Turdus merula )

By N. J. Adams, M. J. Farnworth, J. Rickett, K. A. Parker, J. F. Cockrem

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Capture and temporary confinement of wild birds are integral parts of wildlife management practice and research used, for example, during translocation or reintroduction initiatives. We report here on the behavioural and stress hormone (corticosterone) responses of wild blackbirds (Turdus merula) to capture and short-term confinement, partly consistent with some translocation protocols. We examine also the relationship between behaviour and plasma corticosterone concentrations. Acute capture induced responses in corticosterone concentration, integrated over 60 min, at the commencement and conclusion of a 22-day confinement in aviaries were similar at 669.1+or-66.6 (mean+or-1S.E.) and 678.2+or-115.8 ng/mL/min respectively. However, base levels of corticosterone were higher at final release than at initial capture (6.8 and 2.2 ng/mL respectively, P<0.001). This may reflect that the 3-week period of confinement is a chronic stressor. There was an increased propensity for locomotory behaviours (P=0.001), maintenance behaviours (P=0.032) and alarm vocalisations (P=0.04) over the period of captivity. The frequency of alert behaviours (P<0.001) decreased, probably related to habituation to captivity and possibly an associated decrease in perceived predation or starvation risk. Individual behavioural responses were generally repeatable across all observation days, with locomotory behaviours showing the highest repeatability (Repeatability=0.592+or-0.084, P<0.0001). Significant repeatabilities were also detected for corticosterone concentrations measured at 60 min after capture (Repeatability=0.619+or-0.166, P=0.0007) and corrected integrated corticosterone (Repeatability=0.368+or-0.166, P=0.039) measured on initial capture and on release. We used principle component analysis to generate a composite measure of locomotory, alert and vocalisation behaviours. This measure was positively correlated with corrected integrated corticosterone response at release (P=0.019) when behaviour was summed across all observation days. Corrected integrated corticosterone response at initial capture (P=0.049) was also correlated with this behavioural measure at 20 days after capture. This, in combination with the consistency in the behavioural and corticosterone responses across the period of captivity, may reflect individual differences in coping abilities to confinement that may ultimately predict post-translocation survival.

Date 2011
Publication Title Applied Animal Behaviour Science
Volume 134
Issue 3/4
Pages 246-255
ISBN/ISSN 0168-1591
DOI 10.1016/j.applanim.2011.07.001
Language English
Author Address Department of Natural Sciences, Unitec Institute of Technology, Private Bag 92025, Auckland, New Zealand.
Cite this work

Researchers should cite this work as follows:

  1. Animal behavior
  2. Animal ecology
  3. Animal nutrition
  4. Aviaries
  5. Behavior and behavior mechanisms
  6. Biological resources
  7. Birds
  8. Blood
  9. Cages
  10. Corticosteroids
  11. peer-reviewed
  12. Pets and companion animals
  13. Physiology and biochemistry
  14. practices
  15. predation
  16. repeatability
  17. starvation
  18. survival
  19. temperament
  20. translocation
  21. Wild animals
  22. wildlife
  23. wildlife diseases
  24. wildlife management
  25. Zoology
  1. peer-reviewed