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First published online November 30, 2007
Journal of Experimental Biology 210, 4368-4378 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.007104
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Physiological, morphological and behavioural effects of selecting zebra finches for divergent levels of corticosterone

M. L. Roberts1,*, K. L. Buchanan2, D. Hasselquist3, A. T. D. Bennett4 and M. R. Evans1

1 Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus, Penryn, Cornwall TR10 9EZ, UK
2 School of Biosciences, Main Building, Park Place, Cardiff University, Cardiff CF10 3TL, UK
3 Department of Animal Ecology, Lund University, Ecology Building, Sölvegatan 37, 22362 Lund, Sweden
4 School of Biological Sciences, Woodland Road, University of Bristol, Bristol BS8 1UG, UK

* Author for correspondence at present address: Max Planck Institute for Ornithology, Vogelwarte Radolfzell, Schlossallee 2, 78315 Radolfzell, Germany (e-mail: roberts{at}orn.mpg.de)

Accepted 8 October 2007

The effects of environmental stress on the physiology and behaviour of higher vertebrates has become an important avenue of research in recent years. Evidence from recent studies has suggested that the avian stress-related hormone corticosterone (CORT) may play a role in immunocompetence and sexual selection. We tested whether CORT is immunosuppressive by studying humoral and cell-mediated immune responses in populations of captive zebra finches selected for divergent peak levels of CORT. We also investigated whether selection for peak CORT has an effect on the quality of several sexually selected regions of the male zebra finch; in addition we compared morphometric parameters and the dominance ranking in males from the different selection lines. We also tested whether different components of the immune system compete for limited resources. We found that selection for divergent levels of peak CORT had little effect on humoral immunity, male sexual signal quality or dominance ranking. However, contrary to expectations, we did find a positive relationship between CORT titre and cell-mediated immunity, as well as a greater cell-mediated response in the birds selected for high CORT titre than those selected for low CORT titre. Consistent with predictions, significant negative relationships were found between both testosterone and CORT titre on humoral immunity. Birds from the low CORT lines were significantly larger in terms of skeletal size than those from the high CORT lines. Overall, our results suggest that the cell-mediated immune response is associated with a reduction in the humoral response, but only in males, and that there is no simple relationship between peak CORT levels and immune function.

Key words: corticosterone, glucocorticoid, zebra finch, selection experiment, stress, dominance, immunity, skeletal size, sexual signals, testosterone






© The Company of Biologists Ltd 2007