There's been a decline in the numbers of some migratory songbirds that breed in the forests of North America. One reason for the decline may be that fewer baby birds are making it out of the nest. For some animals, a songbird's nest is a meal in a bowl. Snakes, raccoons and other birds eat eggs and nestlings.
Cowbirds also cause problems.
A mother cowbird lays her egg in a songbird's nest, leaving the songbird parent to raise the cowbird chick at the expense of the songbird's own offspring. Although nest robbing is nothing new, it seems to be on the rise. A study by the U.S. Forest Service suggests that it's partly because of changes in the songbird's forest breeding grounds. A songbird's nest built at the edge of the forest is more likely to get robbed than a nest deep in the forest. That's because nests at the forest edge are more exposed to predators and cowbirds.