Nest Parasitism - Common in Ducks and Other Precocial Birds

The drawing above shows a fundamental difference between waterfowl and most other birds – ducks have precocial young that feed themselves. (Altricial - left, Precocial, right)

Robins typically lay 4 eggs, which is an upper limit set by how many altricial young the parents can feed. Parasitic eggs laid by another robin are very costly to the host due to extra parental work and negative impacts on their genetic young. Accordingly, nests are very closely defended.

In ducks, extra eggs have far less detrimental impact as young feed themselves. Ducks typically lay close to 10 eggs and nests are not defended anywhere near a strongly as in altricial birds.

As a result, in many waterfowl females have an alternative reproductive strategy of laying parasitic eggs.

-Frank