Calcium availability limits breeding success of passerines on poor soils
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Published source details
Graveland J. & Drent R.H. (1997) Calcium availability limits breeding success of passerines on poor soils. Journal of Animal Ecology, 66, 279-288.
Published source details Graveland J. & Drent R.H. (1997) Calcium availability limits breeding success of passerines on poor soils. Journal of Animal Ecology, 66, 279-288.
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This study is summarised as evidence for the following.
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Provide calcium supplements to increase survival or reproductive success Action Link |
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Provide calcium supplements to increase survival or reproductive success
A cross-over study in a mixed forest on calcium-poor soils in the Netherlands from 1990-2 (Graveland & Drent 1997) found that female great tits Parus major supplied with supplementary calcium were more likely to lay eggs (0-3% of supplemented nests empty vs. 10-15% of controls, 622 nests studied) and less likely to desert them (15-25% of supplemented clutches deserted vs. 40-70% of controls, 339 clutches studied). Eggs from supplemented females were less likely to have defective eggshells (15-25% vs. 40-70%, 360 clutches) and a higher proportion of eggs from successful, supplemented nests hatched (80-95% of eggs vs. 55-80% for controls, 204 clutches). There were no significant differences in laying date or clutch size between treatments. This resulted in 5-9 hatchlings/nest for supplemented nests and 2-4 hatchlings/nest for controls. Calcium was provided in the form of 500 mm2 snail shells or chicken eggshells provided three times a week from early March, in feeding cups on the outside of nestboxes. Birds took supplements mostly during the egg-laying and chick-provisioning stages of reproduction.
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