[单项选择]For over 30 years, Donald Kroodsma has worked to disclose such mysteries of bird communication. Through field studies and laboratory experiments, he’s studied the ecological and social forces that may have contributed to the evolution of vocal learning. Kroodsma has paid particular attention to local variation in song types, known as dialects. The Black-capped Chickadees (Parus atricapillus)on Martha’s Vineyard, for example, have an entirely different song than their counterparts on the Massachusetts mainland, he says. Birds that live on the boundary between two dialects or that spend time in different areas can become "bilingual," learning the; songs of more than one group of neighbors. Recently, Kroodsma discovered that the Three-wattled Bellbird (Procnias tricarunculata) is constantly changing its song, creating what he calls a "rapid cultural evolution within each generation. "This kind of song evolution is found in whales but, up until now, rarely in birds.
A professor of bio
A. whales are as constantly changing their song as birds, creating what is known
B. whales are seldom changing their song in the way we find in birds
C. birds are less often changing their songs than whales are
D. birds would never change their songs as whales would do