Photo © Al Tuttle

Why study clutch size?

The topic of clutch size variation has been a source of fascination for generations of bird biologists. We know there is variation in clutch size both within and among species. We want to know more about what factors might influence this variation in clutch size. For example, within a given species, does the number of eggs a female lays per clutch vary with latitude? With altitude? Why do birds that are colonial or nest at relatively high densities often lay fewer eggs than their solitary-nesting relatives? Why do small species tend to have larger clutches than large species? It is almost certainly true that birds lay about the number of eggs that will produce the maximum number of surviving offspring over the parents’ reproductive lifetime. What ecological factors determine this number for different birds?

Increasing our understanding of the biological and ecological factors that affect clutch size allows scientists and wildlife managers to make better-informed decisions about bird conservation.