Brown-headed Cowbird (Molothrus ater) is widely distributed across the U.S. Bronzed Cowbird (Molothrus aeneus) is a southwestern species that wanders as far east as Florida. Males and females have different plumage, but bill shape and thick neck are good field marks. Only Bronzed Cowbirds have the red eye. Cowbirds are nest parasites: female lays eggs in nest of other species after removing original eggs; chicks grow faster and larger than host's own offspring and out feed and kill rivals. Yet somehow young raised by forster parents don't imprint and know they are cowbirds. All images made at various locations in AZ.