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Status: Population size: 1,250

Yellow-shouldered Blackbird
(Agelaius xanthomus)

This species was once widespread across Puerto Rico; now the population is small and fragmented due to cowbird parasitism, habitat loss, and other threats.

Identification
An entirely black bird with yellow shoulder patches, as its name suggests.

Distribution and Population Trends
It occurs in two forms: the monensis race is found on the offshore islands of Mona and Monito; the nominate race occurs on the mainland, primarily on the southwestern coast. This population declined about 80% from 1975 to 1985, dropping to just 300 individuals in 1982. Pre-breeding season roost counts have shown a 14% annual increase, on average. In 1998, estimates for this population were at 1,250 individuals. The species is still seen eastern coast as well, but there have been no breeding records since 1986.

Ecology
The species once inhabited mangroves, pastures, coconut and palm stands, cactus scrub, coastal cliffs, and on occasion, woodland areas. It has always been most common along the coast. Many now breed on the cays, offshore. The nest is cup-shaped and placed in cliff crevices, tree hollows or forks, and the bases of palm fronds. They lay two to four eggs, and breeding takes place from March to September. The species typically breeds in small colonies. They forage in trees as well as on the ground, eating seeds, nectar, and insects, especially moths and crickets.

Threats
Brood parasitism by the Shiny Cowbird has been a major factor in the Yellow-shouldered Blackbird’s decline and has led to the birds’ breeding offshoreThey are also threatened by Caribbean Martins which take over their nesting sites, by nest predation by the Pearly-eyed Thrasher, and extensive habitat loss to agriculture.

Conservation
The species was federally listed as Endangered in 1976. Since 1982, an artificial nest program has been ongoing, and nest success is now being closely monitored. The same conservation program is also working to control cowbird populations, as well as rat and nest mites. The Boguero’n Commonwealth Forest is a mainland stronghold for the Yellow-shouldered Blackbird.

What Can You Do?
The Endangered Species Act has helped protect Yellow-shouldered Blackbird and made it possible to learn critical information about its biology. Audubon continues to work to ensure that this vital legislation is being used to protect our publicly-owned wildlife resources. Check out http://www.audubon.org/campaign/ to learn of the latest news about the Endangered Species Act and how you can help. To learn more about other species protected under this legislation, visit: http://endangered.fws.gov/

Support protection or acquisition of habitat on Puerto Rico by conservation agencies and organizations.

Become a member of the Society for the Conservation and Study of Caribbean Birds. See http://www.nmnh.si.edu/BIRDNET/SCO/.

Audubon is the U.S. representative of the global BirdLife International alliance. Our BirdLife partners in the Caribbean are developing Important Bird Areas programs to identify and conserve critical habitats that support birds and other wildlife. For more information on BirdLife IBA efforts throughout the Americas visit: http://www.birdlife.net/sites/index.cfm

For information about birds of Puerto Rico, including the Yellow-shouldered Blackbird, you can visit the website of the Sociedad Ornitologica Puertorrique?a: http://www.avesdepuertorico.org/main.htm

References
BirdLife International. 2000. Threatened Birds of the World. BirdLife International and Lynx Edicions, Barcelona and Cambridge, United Kingdom.

BirdLife International (2006) Species factsheet: Agelaius xanthomus, Yellow-shouldered Blackbird http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=9714&m=0

Raffaele, Herbert, et.al. 1998. A Guide to the Birds of the West Indies. Princeton University Press, Princeton, NJ.