Plate 84 – Blue-grey Flycatcher

The bird in North America that is the most notorious for brood parasitism is the Brown-headed cowbird (Plate 99). Among the 240 or so different nests that the Brown-headed cowbird will target are those of the Blue-grey Flycatcher. The current common name for the bird is the Blue-gray gnatcatcher. That the Blue-gray gnatcatcher would mistake the egg of the Brown-headed cowbird with one of its own is highly unlikely. The Blue-gray gnatcatcher lays an egg that is about the size of a blueberry. The color of the egg is pale blue and has spots that are reddish or dark brown. The Brown-headed cowbird lays an egg that is more like the size of a large grape. The color of a Brown-headed cowbird egg is white or a grayish white and has spots that are brown or gray. Yet breaking all of the rules of survival of the fittest that Charles Darwin proposed in On the Origin of Species (1859), Blue-gray gnatcatchers will incubate the egg and complete all of the other acts of duty and sacrifice to raise and care for the unrelated chick.