Why do hens lay so many eggs while other birds don't?

Simple answer (and true) is they have been bred to. Coturnix Quail, see: Japanese quail, lay about as many (I kept them in the 1960's). Domestication changes a species. A wolf and a Chihuahua are the same species. read more

As a general rule, birds keep laying eggs until the number of eggs in the nest "looks about right" to them (where "about right" varies from one species to another). If you keep removing the eggs, the birds will keep laying. read more

Men has selectively bred these fowls over many years and kept the ones hat laid more and more eggs, this can be achieved with even wild birds by removing any other than the first 2 eggs laid, she will often continue laying and is indeed a valuable tool to save some species from extinction. read more

5. Certain Breeds Don’t Lay As Many Eggs. Certain breeds just don’t lay as well as others and we sometimes forget this, especially when we read about how great other peoples eggs are. Breeds such as Rhode Island Reds or Buff Orpingtons can lay more than 200 eggs per year. read more