Why do sparrows lay so few eggs?

Every species produces enough offspring to ensure the continuation of the species, under normal circumstances. An animal that produces relatively few offspring has a high survival rate - the odds of any one of the offspring surviving are good - and an animal that produces many offspring has a low survival rate - most of the offspring will die before reaching adulthood.

The "few eggs" produced by a sparrow may be misleading, however. In most of their range, sparrows produce more than one clutch of eggs per year. So even though a sparrow may have only three or four eggs in her nest, she may lay more than a dozen eggs in the course of the spring and summer.

Another possible consideration: Sparrows are often the victims of "nest parasites." I have often seen the nests of house sparrows holding only one egg, which was the egg of a brown-headed cowbird! The sparrow may have laid many eggs, but there was only one in the nest, as the cowbird removed the sparrow's eggs and laid her own for the sparrows to raise.

First answer by Chuckbonner. Last edit by Chuckbonner. Contributor trust: 91 [recommend contributor]. Question popularity: 7 [recommend question]