The Complex Call of the Carolina Chickadee
What can the chick-a-dee call teach us about communication and language?
Parids and Chick-a-dee Calls
Toward the end of summer, many songbirds in temperate regions of the Northern Hemisphere migrate south to overwinter in more favorable climates. But some species stay put. One of the most common groups of resident songbirds is the chickadees and titmice of North America and the tits of Europe and Asia. These small songbirds (they typically weigh less than 30 grams) live in a wide range of habitats, often in heterospecific flocks—mixed-species groups that include other songbird and woodpecker species. Conspecific—composed of a single species—flocks of parids are often territorial and are reported to range in size from two (as in oak titmice, Baeolophus inornatus, which occur only as female-male pairs) to dozens of individuals (as in great tits, Parus major, which form large assemblages with fluid membership). Parids that form flocks do so in the late summer months and often remain in them until the following spring, when female-male pairs establish breeding territories. Such a flock structure, with stable groups of unrelated individuals, is atypical for songbirds and, as we argue below, may be an evolutionary force affecting vocal complexity in these species.
Vocalizations in birds are often divided into two categories: songs and calls. Songs are typically given in the mating season and are directed toward mates or potential rivals. Calls are any other vocalization, and they fall into functional categories, such as food calls, contact calls, mobbing calls or alarm calls. In almost all songbirds, songs are complex and calls are simple. Not so with parids: Many species have relatively simple songs (for example, the fee bee song of black-capped chickadees, Poecile atricapillus, and the peter peter song of tufted titmice, Baeolophus bicolor), but at least one very complex call system—the chick-a-dee call. The name “chickadee” for the North American Poecile group of parids is the onomatopoeic rendition of this call. Interestingly, it is labeled the si-tää call in willow tits, Poecile montanus, which are native to parts of Europe and Asia. When spoken in Swedish, Norwegian or Latvian, si-tää sounds quite similar to the birds’ call.
In winter months in many regions, the only bird sounds you may consistently hear are chick-a-dee calls. The source of those calls is likely to be a group of parids interacting with one another and with any number of other species of birds. Parids are commonly the nuclear species—the core members of mixed-species flocks; they are often joined for periods of time by satellite species such as nuthatches, kinglets, woodpeckers, goldcrests and treecreepers. The behavior of these nonparid species is affected by the presence or absence of parids and also by the parids’ chick-a-dee calls. As such, understanding social cohesion and group movement of these mixed-species flocks requires an understanding of parid signaling systems.