What is the largest North American passerine thought to have hosted the egg of a brood parasite?
In North America north of Mexico, we immediately think of the cowbirds when we think of brood parasites–birds that lay their eggs in the nests of other birds, of the same or a different species. While the cowbirds are the only North American species that breed only by using this fascinating strategy, many others–”facultative” brood parasites–are known to have given it a whirl.
Both Black-billed and Yellow-billed Cuckoos, for example, occasionally deposit their eggs in alien nests, as do their relatives the roadrunners. The largest passerine to have hosted such an egg is the largest passerine in North America, a Common Raven whose nest held the egg of an ambitious Greater Roadrunner.
