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A song is a stereotyped vocalization that is usually long and complex and is used to defend territory and/or attract a mate. Notice the word 'usually'. There are many birds that have short, simple songs -- Henslow's sparrow and the least flycatcher are examples. But, we still call these simple vocalizations songs, because the birds use them in the same way that a song sparrow uses its song, for example.
Calls are basically all of the vocalizations that a bird makes other than its songs. Calls are usually short, simple vocalizations that are used in many contexts such as predator alarm, feeding, courtship, aggression, and social contact. Once again, notice the word 'usually'. Some calls really are simple (chip calls, for example), but others, such as the black-capped chickadee's namesake call -- chickadeedee --, are complex. Many birds make the same basic call in a variety of ways; a crow uses many versions of the basic caw, for example. Some calls may be made by only one sex, but other calls may be made by both sexes.
Scientists sometimes use other definitions of songs and calls for their research, but these are widely accepted ones.
Some birds sing only one song, some have a repertoire of many songs, while others don't have a song. The size of an individual bird's repertoire depends on its species, sex, age, and sometimes who its neighbors are. In some species a bird has its full repertoire when it is one-year old, while in other species a bird seems to add (and maybe lose) songs throughout life. The repertoire size and the pattern of singing are given for several species of North American birds in the following table.
|Species||Repertoire Size||Singing pattern and comments|
|Cedar waxwing||0||A songbird that has no song.|
|Black-capped chickadee||1||Each male has only one song type, but he may change pitch.|
|White-crowned sparrow||1||Shares song with neighbors giving rise to local dialect.|
|Ovenbird||2||Sings only one song during the daytime, but sings a different song at dawn and sometimes at night.|
|Dark-eyed junco||3-7||Repeats a song many times before singing another.|
|Chestnut-sided warbler||about 10||Has two types of songs: about 4 category I songs that are sung during the day and used to attract and keep a mate, and a half dozen category II songs that sung at dawn and during the day when interacting with males and are used to keep territory. Repeats a song many times before changing to another; an individual may know several songs but favor one of them.|
|Song sparrow||4-12||Usually repeats a song many times before changing to another. May share songs with a neighbor.|
|Red-eyed vireo||13-117||Moves immediately from one song to another and usually sings many songs before repeating one.|
|Northern mockingbird||53-150||Usually repeats song or song phrase several times before changing to another song. Gifted mimic.|
|Gray catbird||up to 400||Moves immediately from one song to another and usually sings many songs before repeating one.|
|Brown thrasher||1500-2000+||Largest known repertoire. Usually sings a song twice and then sings a different one. Does he improvise?|
Females of at least 40 species birds sing at least occasionally, but in most species males seem do all the singing. A female northern cardinal will sometimes countersing with her mate. A female red-wing blackbird sings a simple song to defend her nest territory from other females in her mate's harem. Females of several species of wood-warblers sing occasionally. Female song is thought to be more common in tropical species, and since very few have been studied carefully, female song is probably more widespread than we think.
A duet is just what you might think; two birds of the same species singing in a distinctly coordinated manner. Duetting birds may sing synchronously (at the same time), alternately (taking turns) or simply one right after the other. The two songs may be so well coordinated that it sounds like one bird singing. Here are three different synchronous duets by Hunter's cisticola, a small African bird. While duetting the pair of cisticolas perch near each other on a shrub; one bird sings a rolling trill while the other whistles a piping accompaniment.
Flight calls are simply the calls made by birds while in sustained flight. The term is somewhat misleading, however, as birds often make the same calls while perched or on the ground. In fact, the use of flight calls to identify night-flying migrating birds is based, in part, on recordings of perched birds. Migrating birds may use flight calls to keep contact with other members of the flock