Effects of Brown-headed Cowbirds on the nesting success of Chipping Sparrows in southwest Colorado

Article Abstract:

Research is presented concerning the parasitism of Chipping Sparrow nests by Brown-headed Cowbirds in Colorado. Although 17 out of 77 nests were parasitized the main cause of nest failure was predation.

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The head-down display in shiny cowbirds and its relation to dominance behavior

Article Abstract:

The head-down display ofthe shiny cowbird is thought to be an interspecific appeasement behavior. Therewere no differences in the frequency of this display between captive and free-ranging cowbirds. The displays were directed at other species but never ata cospecific, and occurred throughout the year. This behavior is thought to increase the fitness of practicing cowbirds by allowing them to dominate other birds and assist into their integration into potential host flocks.

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Does Brown-headed Cowbird egg coloration influence Red-winged Blackbird response towards nest contents?

Article Abstract:

The importance of Brown-headed Cowbird egg coloration and maculation in the acceptance or rejection of variousobjects placed in the nests of Red-winged Blackbirds was studied. Red-winged Blackbird nests were located and marked with coded flagging tape. Various objects were then added to the nests prior to the time when Brown-headed Cowbirds normally lay their eggs. Results revealed that cowbird egg coloration helps conceal the objects so that they are eventually accepted by Red-winged Blackbirds.

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