Male and female cardinals recognize each other during breeding season not by their plumage, but by differences in their songs, a Columbia University researcher has discovered.
Both male and female cardinals learn their songs, a trait that is exceedingly rare in the animal kingdom, and is also found only in parrots and other avian mimics, dolphins and whales. Scientists study these species to discover more about how songs are learned, information that could show how human babies acquire speech -- a process that is still not fully understood.
By working with baby cardinals, Ayako Yamaguchi, postdoctoral research scientist at Columbia, found that male birds can learn songs from adult females, and females from males. But as the birds grow, their songs become different, probably as the result of hormonal changes.
"If they are learning to sing, how is it that all males sound one way, and all females sound a different way?" Dr. Yamaguchi asked. Her work appears in the August issue of Condor magazine.
Cardinals, which had previously ranged from Central America to Florida and Arizona, have become common in North America only in the last century, mainly because humans have provided food that allows the hardy bird to survive the winter. The male is bright red, the female brown with a pinkish orange head.
Ornithologists had never distinguished between male and female cardinal songs, since there is no distinction between the two to human ears and because most scientists assumed that female cardinals, like the females of most songbird species, don't sing at all. Dr. Yamaguchi was intrigued that cardinals sing only during breeding season from early spring to midsummer, and reasoned that, since the birds normally inhabit dense underbrush that hides them from view, their songs might provide the cue that alerts a bird to the presence of another bird.