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Biologist's research discovers most promiscuous bird

January 5, 2010

Coastal Carolina University biology professor Chris Hill has discovered that the Saltmarsh Sparrow, a shoreline bird that populates the eastern coast, exhibits "extreme levels of multiple mating," making it probably the most promiscuous bird in the world.

The remarkable findings of the new research have been published in The Auk, the journal of the American Ornithologists Union. Hill collaborated with Chris Elphick of the University of Connecticut and Carina Gjerdrum of the Canadian Wildlife Service.

The sparrows, which mate and nest along the coast from Virginia to Maine, are characterized by "scramble-competition polygyny," according to Hill. When the females are ready to mate, they may mate with more than one male, and the males, instead of fighting each other openly for access to females, compete quietly to outmaneuver other males to fertile females.

Out of 60 broods tested, 57 of them had at least two chicks with different fathers. And 97 percent of the females were mating with more than one male.

"Frequently, every single egg in a nest would have a different father," says Hill, who conducted molecular analyses of paternity in his laboratory at CCU. Blood samples were gathered from chicks in the nest and from adults on the breeding grounds, then tested to determine paternity. Elphick and Gjerdrum conducted most of the field work.

Before Hill's study, the species had been known to lack the pair bonds common to most songbirds wherein the parents nest and raise the young together. Instead, the female sparrows nest and feed the young with no assistance from the males.

The sparrows, whose muted grey and brown markings help them blend into their natural environments, winter in similar habitat, sometimes along the coastline of the Carolinas. They spend their entire life in salt marshes, which makes them vulnerable to habitat loss as sea levels rise, notes Hill. This is a species whose future is in question. They need watching.? Hill was assisted by Scott Tomko and Katie Copenhaver, recent CCU graduates, and Whitney Bryan, a student from the South Carolina Governors School for Science and Math.

The sparrows are thought to be even more promiscuous than the previously known extremes of multiple mating, the Greater Vasa Parrot of Madagascar and the Superb Fairy-Wren of Australia.

Hill has been on the faculty at Coastal Carolina University for 10 years. An associate professor of biology, he earned a bachelor's degree from the University of Massachusetts, a master's degree from Eastern Kentucky University and a Ph.D. from the University of Washington.

Hill is currently studying the nesting ecology of Least Terns in South Carolina.