UNIVERSITY PARK, Pa. -- State waterfowl experts have forecast that hunters and bird watchers will see a similar number of ducks migrating over and stopping briefly in Pennsylvania this fall as in recent years, with one exception. The number of black ducks is expected to be down.

Dwindling numbers of migrating wild ducks had been a concern for wildlife managers for decades, but their populations traveling the Atlantic flyway have stabilized in recent years. Researchers in Penn State's College of Agricultural Sciences have found that the growing scarcity of black ducks is not due to habitat problems in northern nesting grounds, but rather to them successfully breeding -- with mallards.

"Black ducks and mallards are morphologically and behaviorally similar," says Margaret Brittingham, professor of wildlife resources, who conducted the study along with Judith Mank and John Carlson from the School of Forest Resources at Penn State. The research was published in a recent issue of the journal Conservation Genetics. "Until relatively recently, black ducks were an isolated offshoot of the much larger mallard population. Since 1940 or so, hybridization of black ducks and mallards has resulted in fewer black ducks."

According to Brittingham, habitat alteration that accompanied European settlement in the Northeast and game farm mallard releases in the last 200 years have enabled mallards to colonize territory east of the Appalachian Mountains, where they had only been rare wanderers before. "By 1969, mallards outnumbered black ducks in the Atlantic flyway," she says. "This population trend has continued to the present day and has resulted in hybrid progeny that backcross into the parental populations, leading to fewer and fewer black ducks."

Some scientists argue that black ducks were never a true species, but rather a color morph or subspecies of the mallard population. "We could not answer this question by looking at present day mallards and black ducks," Brittingham says. "By studying modern specimens alone, we can't tell if the present-day genetic similarity of mallards and black ducks is an ancestral condition or the result of secondary gene flow from repeated hybridizing." However, by looking at museum specimens of black ducks and mallards collected before mallards were common in the East and comparing them with modern specimens, the researchers could determine if mallards and black ducks were always genetically very similar or whether this similarity had occurred recently.

The Penn State scientists conducted DNA tests on 135 duck wings obtained from the Atlantic Flyway parts count done by the U.S. Fish & Wildlife Service. The wings, collected from hunters from Maine to South Carolina, came from 45 mallards, 42 black ducks and 48 hybrids. To examine DNA from ducks taken before 1940, researchers collected feathers from museum specimens.

"What we found from DNA testing was that historically mallards and black ducks were very different genetically, and they have become much more similar in recent decades due to hybridization," says Brittingham. "Because the mallard population is so much bigger to begin with, the effect is greatest on the black-duck population. In looking at the DNA of modern specimens, black ducks are no longer very distinct from mallards, and we are losing the unique species known as the black duck. We believe that's why we are seeing fewer of them, and we are concerned that without preventing hybridization, conservation of black duck habitat will not be sufficient to preserve this species."

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EDITORS: Contact Margaret Brittingham at 814-863-8442 or by e-mail at mxb21@psu.edu.

Writer/Editor: Jeff MulhollemOffice 814-863-2719