Not really gross, but actually quite beneficial!
Through my camera’s lens, I thought this sweet little Song Sparrow was hopping around with a breakfast of leaves until downloading the photos. Rather, his mouth is stuffed with what appears to be the larvae of the Winter Moth, those annoying little green caterpillars that dangle from trees, which pupate into the dreaded adult Winter Moths, which are destroying trees and shrubs throughout the region. So, thank you Song Sparrow!
The Song Sparrow was most likely bringing the caterpillars to its nestlings. Although adult Song Sparrows prefer seeds, to a newly hatched bird a plump juicy green caterpillar is easy to digest and rich in nutrients. As a matter of fact, most songbirds rear their young on insects. The Song Sparrow photo illustrates yet another reason why it is so important not to spray trees with pesticides and herbicides. When a landscape is pesticide free, a natural balance returns. Insects are bird food!