One of the most abundant birds visiting my feeders right now is the brown-headed cowbird. I find it remarkable this bird is so common since it does not build a nest or raise its own young; these tasks are left to others. Indeed, it is the epitome of a nest parasite.
Biologists tell us the brown-headed cowbird has been documented laying its eggs in the nests of more than 220 species of birds. This includes the likes of the northern cardinal, warblers, brown thrasher, eastern phoebe, sparrows, tanagers, gray catbird, northern mockingbird, and even hummingbirds. In addition, 140+ species of birds are known to have raised young cowbirds.
During the nesting season, a female brown-headed cowbird lays an egg per day over a period spanning forty days. Rarely does she lay more than one egg in a nest.
The photo depicts a female (the drab bird) and male brown-headed cowbird.
One the average only three percent of the young cowbirds will successfully fledge. While this may not sound like many, at this rate a cowbird population can double itself every eight years.
If the number of cowbirds currently visiting my feeders is any indication of the numbers of cowbirds that have successfully fledged during the past few years, the brown-headed cowbird population is definitely on the rise in my corner of the world.