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Accession Number 5004433

Title North American Cowbird Advisory Council

Project Description The North American Cowbird Advisory Council serves as an authoritative source of guidance and

information on ecology and management of parasitic cowbirds. Three cowbird species are found in

North America: (1) the Brown-headed Cowbird (Molothrus ater) has a national range and presently

causes the most problems; the South American Shiny Cowbird (M. bonariensis) invaded Florida

10 years ago and is becoming established in the southern peninsula; the Central American

Bronzed Cowbird (M. aeneus) invaded Texas atleast 10 years ago and is well established in the

Rio Grande valley. The North American Cowbird Advisory Council was established to serve the

DOI agencies as well as state and local agencies with responsibilities for land and resource

management. A particular focus is the regional monitoring and control program run by DOI

agencies (FWS, NPS, BLM, BOR)in 5 southwestern states to protect the newly listed

Southwestern Willow Flycatcher. The council's members include experts on the biology of cowbird

parasitism and on the biology of the endangered species for which cowbird parasitism has been

identified as a problem in the recovery plans. Council members include representatives of the

university scientific community, federal agencies, and private environmental community. Co-chairs

are Caldwell Hahn, PWRC, and Stephen Rothstein, UC Santa Barbara. These invasive cowbird

species are a cause for management concern because of their extraordinary capacity for range

expansion in conjunction with human development and because of the large number of songbirds

that are affected by their parasitism. The Brown-headed Cowbird has expanded its range from the

Great Plains to the entire continent over the course of the European colonization of North

America. It has had a serious negative impact on 4 endangered species as well as on numerous

other songbirds. The Brown-headed Cowbird is a complex species to characterize ecologically

because it is an extreme host generalist, parasitizing 200 species and exploiting a staggering

array of habitats. There is growing uneasiness at the high expense and indefinite duration of the

large number of cowbird control programs that have been initiated across the nation as well as at

the lack of information about basic cowbird breeding biology necessary to estimate the cowbird's

impact on declining species. The two other cowbird species that have invaded the US much more

recently are not as well studied or understood, but they are invading areas where songbirds are

already subject to loss of habitat and heavy pressure from human development. The degree to

which the 3 parasitic cowbird species will overlap and parasitize hosts in the same communities

is unknown.

Keywords biological control, brood parasitism, ecosystem science, endangered species, information

transfer, invasive species, monitoring, rangeland management, standards and protocols, status

and trends,

Principal D. C Hahn, USGS Patuxent Wildlife Research Center:;


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