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.


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.


Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 18

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust