Shiny Cowbird – McCuration

Shiny Cowbird

Molothrus bonariensis

The Birds of the World website introduces the Shiny Cowbird with this descriptive information: Shiny Cowbirds are generalist brood parasites. Their arrival in North America raises concerns for potential host species. In the West Indies, this concern has fostered studies of the endangered Yellow-shouldered Blackbird (Agelaius xanthomus) and island endemic Puerto Rican Vireo (Vireo latimeri) and their interaction with Shiny Cowbirds. Opportunistic in its feeding behavior and choice of hosts, the Shiny Cowbird is in many respects the South American counterpart of the Brown-headed Cowbird. Shiny Cowbirds usually are associated with open, disturbed areas such as agricultural regions, and often ride on the backs of cattle, horses, and sheep while feeding. It appears to differ from the Brown-headed Cowbirds in being more insectivorous, and in feeding higher off the ground. In some regions, it may specialize in parasitizing marsh-nesting blackbirds, particularly Agelaius species. It also more frequently parasitizes cavity-nesting hosts. What little is known about the mating systems of the Brown-headed and Shiny cowbirds suggests that both species are labile, varying from monogamy to polygamy-polygyny, depending perhaps on host availability.

I met my first Shiny Cowbird on Thursday morning, August 31, 2023. Our Jeff Parker Tour group was staying at Southwild’s Pouso Alegre Lodge and on this morning I was hanging out at the main feeder at the Lodge. Our guide Liko was kind enough to explain to me the three types of Cowbirds in terms of their size. The Screaming Cowbird is the smallest, the Shiny Cowbird is in the middle, and the Giant Cowbird is by far the largest. All three of these cowbirds were present at the feeder. For details of my Brazilian trip that include the sighting of this bird, look here. Below are a couple of my photos of this bird. In each of the photos, the Shiny Cowbird is the larger black bird on the right, with the bluish tint.