REALLY?

Does bird mating ever cross the species line?

“Many birds occasionally mate with members of other bird species, producing hybrid offspring,” said Irby J. Lovette, director of the Fuller Evolutionary Biology Program at the Cornell Lab of Ornithology.

In fact, Lovette said, about 10 percent of the world’s 10,000 bird species are known to have bred with another species at least once, either in the wild or in captivity. For example, in the eastern United States, native black ducks have hybridized so often with the more abundant mallard ducks that pure black ducks have become rare.

Hybridization tends to occur between species that are closely related, Lovette said, but an individual from one genus may occasionally form a pair with a bird from an altogether different genus, separated by many millions of years of evolutionary divergence.

Some groups of birds are particularly prone to hybridization, he said, adding:

“Experienced bird watchers know to watch out for the occasional hybrid gull or duck that exhibits an odd mix of its parents’ colors and behaviors. Often, however, hybrids die young, and even when hybrid offspring survive until adulthood, they may be sterile or have trouble attracting mates.”

When hybrid offspring do not pass on their genes, the mating that produced them cannot be considered totally successful, Lovette said. Indeed, much of the entrancing diversity of the avian world, like colors, plumes, songs and bizarre mating displays, “has arisen in part because these differences help female birds avoid accidental matings with a male of a different species,” he said.