Present address: Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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What causes the decrease in haematocrit during egg production?
Article first published online: 14 MAY 2004
DOI: 10.1111/j.0269-8463.2004.00829.x
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How to Cite
WILLIAMS, T. D., CHALLENGER, W. O., CHRISTIANS, J. K., EVANSON, M., LOVE, O. and VEZINA, F. (2004), What causes the decrease in haematocrit during egg production?. Functional Ecology, 18: 330–336. doi: 10.1111/j.0269-8463.2004.00829.x
Publication History
- Issue published online: 14 MAY 2004
- Article first published online: 14 MAY 2004
- Received 4 September 2003; revised 6 October 2003; accepted 22 October 2003
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Keywords:
- Aerobic performance;
- cost of reproduction;
- egg-laying;
- hematocrit
Summary
- 1Anaemia has been reported in wild animals, typically associated with traumatic events or ill health. However, female birds routinely become ‘anaemic’ during egg-laying; we sought to determine the causes of this reduction in haematocrit.
- 2Haematocrit in female European Starlings (Sturnus vulgaris Linnaeus) decreased between pre-breeding and egg-laying in 3 out of 4 years (the decrease was marginally non-significant in the fourth year). This was independent of changes in ambient temperature altering the metabolic requirements for thermoregulation.
- 3There was a positive relationship between haematocrit and plasma levels of the yolk precursor vitellogenin among egg-laying birds, supporting the hypothesis that the initial reduction in haematocrit is caused by increased blood volume associated with osmoregulatory adjustments to elevated levels of yolk precursors.
- 4However, haematocrit did not always recover upon cessation of egg production, remaining low at clutch completion (2 of 4 years), incubation (1 of 2 years) and chick rearing (1 of 4 years), suggesting an additional cause of the prolonged reduction in haematocrit.
- 5Given the magnitude and prolonged nature of the changes in haematocrit we report, and the interannual variation in haematocrit even during chick-rearing (47–54%), we suggest that ‘anaemia’ associated with egg production might have implications for aerobic performance during later stages of breeding.