The Greater Racket-Tailed Drongo, a conspicuous black bird with a deeply forked tail, often forages in flocks comprised of up to a dozen different species of birds. The drongo perches above the flock, snatching insects that they disturb, and keeping an eye out for predators that might go unnoticed by its hunting flock-mates. The associated bird species seek out drongos, apparently relying upon them heavily for protection. Drongos feed more effectively when in such flocks, so the benefits go both ways.
Recent studies in Sri Lanka have revealed that, upon sighting a predator, a drongo will imitate the alarm calls of at least 4 other bird species (babblers, laughing thrushes, bulbuls and others), as well as the call given by the specific predator, i.e. a giant squirrel or eagle.
When unthreatened but hungry, the drongo will attract other birds to itself by imitating their calls – but this time it utilizes contact calls or mating calls. It very effectively forms a small foraging group in this manner. So, the drongo is not only choosing the calls of other species, but it’s using them in the correct context – hawk as opposed to snake, feeding as opposed to mobbing. In essence, the bird is a true linguist. When presented with a human intruder, one drongo improvised – after a very short “assessment” it gave forth the call of a Crested Serpent Eagle (perhaps because this is the largest predator it normally encounters?).
Male European Starlings, incidentally, mimic the calls of other birds in order to impress their mates. An individual I visited often as a child, kept at the American Museum of Natural History in NYC, was able to imitate several words as well.
Some parrots seem to exhibit a quite detailed knowledge of what they are saying.
An abstract of an article dealing with research similar to that mentioned above is posted at:
This image was originally posted to Flickr by Kai Hendry at http://flickr.com/photos/16105436@N00/99531708. It was reviewed on 09:53, 17 August 2007 (UTC) by FlickreviewR, and confirmed to be licensed under the terms of the cc-by-2.0.