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Earth Matters : Why do animals communicate?

By David Spector

For many years my research brought me outside in May and June about an hour before sunrise to hear and record yellow warblers. Males in breeding season sang intensively for a half-hour or so, and, depending on their mating status, sang in a somewhat different style and less intensively well into the morning. Females often responded to male song with “chip” notes, and both sexes used a variety of short calls. Each vocalizing bird revealed its location, and often much more information — its species, its sex, its individual identity, its mating status, its willingness to fight if approached by another of the same species and sex, and perhaps more about its behavioral state. Such information is valuable, possibly affecting the bird’s survival. Why share it? How might sharing this information benefit the individual animal? I suggest three answers to these questions: leakage, manipulation and probing.