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Molothrus rufoaxillaris

Screaming Cowbird

  • Order: Passeriformes
  • Family: Icteridae
  • Monotypic

Authors: Lowther, Peter E

Molothrus rufoaxillaris

Matador/Bom Retiro, SC, Brazil; 26 July 2008 © Cesar Dario Lins

The Screaming Cowbird is a specialist brood parasite, parasitizing almost exclusively the Bay-winged Cowbird (Agelaioides badius). This host-parasitic relationship was first realized on 12 April 1873 by W. H. Hudson (1874, 1920) when he collected, from a flock of Bay-winged Cowbirds, young Screaming Cowbirds, which were molting from their "Bay-winged" juvenile plumage to the "Screaming Cowbird" adult plumage. Hudson then understood that the "extra" eggs in Bay-winged Cowbird nests must be those of the Screaming Cowbird -- "the eggs of the two species are identical in form, size, and coloration, and that, stranger still, the mimicry is as perfect in the young birds as in the eggs" (Hudson 1874: 162; see also Hudson 1920: 104). Because of this in-the-nest similarity, information of both species are presented for comparative purposes in some sections of this account.

Recommended Citation

Lowther, Peter E. 2011. Screaming Cowbird (Molothrus rufoaxillaris), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online: http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=34766

This map provided by Robert S. Ridgely.

  • Migration/Movement:Resident (nonmigratory)
  • Primary Habitat:Second growth scrub
  • Foraging Strata:Terrestrial
  • Foraging Behavior:Glean
  • Diet:Terrestrial invertebrates
  • Sociality:Solitary/Pairs
  • Mating System:Monogamy
  • Nest Form:Nest Parasite
  • Clutch: -
  • IUCN Status:Least Concern