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Screaming Cowbird Molothrus rufoaxillaris

  • Order: Passeriformes
  • Family: Icteridae
  • Monotypic
  • Authors: Peter E. Lowther


Geographic Variation

No described variation.

Related Species

The five species of "true cowbirds" (Molothrus) are brood parasitic; Bay-winged Cowbird (Agelaioides badius) of southern Brazil, Bolivia, and northern Argentina is non-parasitic. Herbert Friedmann's (1929) proposed phylogeny of the cowbirds placed the non-parasitic Bay-winged at the base, and the morphologically similar Screaming as the most "primitive" parasitic cowbird. He presented a seemingly reasonable ordering of cowbird taxa showing development of brood parasitism from a nest parasite to specialized one-host brood parasite to other more generalized brood parasites. More recent biochemical studies have shown the need to re-think cowbird systematics and the evolution of brood parasitism among the Icteridae. Phylogenetic analysis of mitochondrial DNA sequence data indicate that the five species of parasitic cowbirds comprise a natural (= monophyletic) group which does not include Bay-winged Cowbird (Lanyon 1992). The Screaming Cowbird is at the base of this cowbird clade, and the Bay-winged Cowbird is not actually Molothrus in the strict sense (Lanyon 1992; Johnson and Lanyon 1999). Analysis of restrictive enzyme cleave sites in mitochondrial DNA produces a tree in which Screaming Cowbird is not a sister-group to any other Molothrus (Freeman and Zink 1995). Combining restriction site data with sequence data generates the phylogenetic topology of Lanyon (Freeman and Zink 1995).  (Data for presence/absence of 161 restriction sites for 49 icterids – including all Molothrus species – are included in Freeman and Zink 1995.)

Recommended Citation

Lowther, P. E. (2011). Screaming Cowbird (Molothrus rufoaxillaris), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.