Why do some bird species lay only 1 egg?
Why do some species of birds lay only one egg in their nest, while others lay 10 or more? A global study of the wide variation among birds in this trait, known as the “clutch size,” now provides biologists with some answers. The study, published in the current issue of the journal PLoS Biology, combined data on the clutch sizes of 5,290 species of birds with information on the biology and environment of each of these species. “With this approach, we were able to explain a major proportion of the global variation in clutch size and also to predict with high confidence the average clutch size for types of birds living and breeding in certain environments,” said Walter Jetz, an associate professor of biology at UC San Diego and the senior author of the study. “For example, cavity nesters, such as woodpeckers, have larger clutches than open-nesting species. And species in seasonal environments, especially those living at northern latitudes, have larger clutches than tropical birds.” Clutch
