Resplendent egss of Great Tinamou, which has a geometric mean clutch size
of 4.2.
Photo / Cagan Sekercioglu
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Half the world birds lay two eggs, some even ten; UC San
Diego study brings clarity
9 December 2008
Author Summary
Why do some bird species lay only one egg in their nest, and others
ten? The clutch size of birds is one of the best-studied life-history
traits of animals. Nevertheless, research has so far focused either
on a comparative approach, relating clutch size to other biological
traits of the species, such as body weight; or on a macroecological
approach, testing how environmental factors, such as seasonality,
influence clutch size. We used the most comprehensive dataset
on clutch size ever compiled, including 5,290 species, and combined
it with data on the biology and the environment of these species. This approach enabled us to merge comparative and macroecological
methods and to test biological and environmental factors together
in one analysis.
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With this approach, we are able to explain a
major proportion of the global variation in clutch size and also
to predict with high confidence the average clutch size of a bird
assemblage on earth. For example, cavity nesters, such as woodpeckers,
have larger clutches than open-nesting species; and species in
seasonal environments, especially at northern latitudes, have
larger clutches than tropical birds. The findings offer a bridge
between macroecology and comparative biology, and provide a global
and integrative understanding of a core life-history trait. ...
read
the full story from the Press Room of University of California,
San Diego.
Research Article
The
Worldwide Variation in Avian Clutch Size across Species and Space
Jetz W, Sekercioglu CH, Böhning-Gaese K (2008)
PLoS Biology Vol. 6, No. 12, e303 doi:10.1371/journal.pbio.0060303
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