A study published in January found that male Song sparrows sing a repertoire of up to 12 two-second songs in sets lasting about 30 minutes – repeating a single song many times in a row within each set. During the next set, the males repeat the same 12 songs, but this time, vary the length of each individual song.
It was thought that the variation in song lengths was random, but this new study, conducted by researchers from Duke University, found that males vary their song lengths according to a specific pattern. If a song was repeated ten times in one set, it is sung only once or twice in the next set, and a song that was sung only a few times in the first set was sung much more often in the next.
Whether or not this variation is intended to make their sets more interesting to potential mates, it does mean that male Song sparrows can retain a memory of their song lengths and order for at least 30 minutes. This is more 360 times longer than was previously thought. The former record-holder for retaining song-length memory was the canary, which varies its songs only within a five-second time span. Song sparrows truly are the sparrows of song.