We received an email from Larry & Angie in Innisfail a while ago, asking for help identifying a bird in their yard. They were confused because this bird was acting like a baby sparrow, being fed by an adult sparrow but appeared to be bigger than the adult. Their photogenic picture does a wonderful job of showing a juvenile Brown-headed Cowbird in action, and the difference in size between the two species.
As Matthew mentioned in his July Cowbird Catastrophe post on this blog, Cowbirds do not look after their own eggs, but lay them in the nests of other species. This poor Chipping Sparrow has already been outsized by this demanding youngster, and continues to burn up energy finding enough food for it. As Cowbird eggs hatch sooner than those of other birds and fledglings are known to eject the nest occupants, it’s likely this Chipping Sparrow did not raise any of his own young this year.
Posted by Pat Bumstead