Abstract
Current research in birds suggests that a conflict should exist during reproduction for the role of the glucocorticoid corticosterone (CORT). While elevated levels have been correlated with the increased energetic demand of raising offspring, elevated CORT levels have traditionally been implicated in reproductive abandonment. We examined the relationship between CORT and nest desertion in breeding wild female European starlings (Sturnus vulgaris) incorporating analyses of both total circulating levels and 'free', unbound CORT through analysis of corticosteroid-binding globulin (CBG). Free baseline CORT levels of nest-abandoning birds were significantly higher than nonabandoning birds within each stage, with chick-rearing birds exhibiting the highest free baseline CORT levels, while concurrently remaining the most resistant stage to nest desertion. Elevated free baseline CORT levels in chick-rearing birds were not due to increased total CORT secretion, but rather to a decrease in CBG levels. Overall, our results suggest that CORT and CBG interact to play a role in mediating the increased energetic demand of offspring, while minimizing the chances of nest desertion, thereby alleviating any potential behavioral conflict for CORT during reproduction. Furthermore, these results demonstrate that the traditional view of the role of CORT during reproduction is much more complex than previously appreciated. Together with mounting evidence, we suggest that elevated corticosteroid levels are an inherent and necessary part of reproduction in nonmammalian tetrapods.
| Original language | English |
|---|---|
| Pages (from-to) | 59-65 |
| Number of pages | 7 |
| Journal | Hormones and Behavior |
| Volume | 46 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jun 2004 |
Funding
We wish to thank John Wingfield for the generous use of his laboratory during sample analysis for corticosterone and Lynn Erkman for her assistance with sample analysis. We would also like to thank Haruka Wada and John Shyu for their extensive assistance during sample analysis of CBG and two anonymous reviewers for invaluable comments and contributions that greatly improved this work. Finally, we would like to thank Tom Scott and Lee Struthers from the Pacific Agri-Food Research Center for providing the field laboratory. This research was funded by an operating Natural Sciences and Engineering Research Council of Canada (NSERC) grant to T.D.W., a National Science Foundation (NSF) research grant (IBN-0202676) to C.W.B, a NSF research grant (OBN-9905679) to John Wingfield and postgraduate funding to F.V. from NSERC and Fonds pour la Formation de Chercheurs et l'Aide à la Researche (FCAR).
| Funder number |
|---|
| OBN-9905679, IBN-0202676 |
Keywords
- Corticosteroid-binding globulin
- Corticosterone
- European starling (Sturnus vulgaris)
- Nest desertion
- Reproduction