Canadian Researchers have found that closely related birds that share the same habitat tend to look and sound different.
This evolutionary rule of thumb seems to help birds to identify members of their own species.
Dr Paul Martin and his team studied 250 bird species throughout the world. With the help of the Macaulay Library of birdsong, they were able to compile a database of where the birds lived and what they looked and sounded like.
“We found, repeatedly, that birds that [live in the same location] with a close relative have more divergent songs and colour patterns,” Dr Martin told BBC Nature.
“So it looks like costs of sharing a location with a relative drives some of the amazing variation we see,” he pointed out.
Dr Martin said that he was drawn to studying birds precisely because he was fascinated by their variety.
For a bird species, being distinct could actually be crucial for survival.
“Being different in songs and colour is really important to identify your own species and to avoid mating outside your own species,” explained Dr Martin.
“Colour patterns and songs are traits that are really used for mate attraction and choice… so these are the traits we would expect to diverge.”
Being different could also help ensure that birds are not inappropriately “picked on” during competition for food and territory.
Dr Martin presented the findings at the First Joint Congress for Evolutionary Biology in Ottawa.