Study

Calcium availability limits breeding success of passerines on poor soils

  • 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.

Actions

This study is summarised as evidence for the following.

Action Category

Provide calcium supplements to increase survival or reproductive success

Action Link
Bird Conservation
  1. 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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