'Cheating' male flycatchers change their tune, and females can tell

Imagine if you could tell whether someone was already married just by listening to the way they talk.

Female pied flycatchers, small birds, can do something like that!

A male bird sometimes finds a mate and then moves to another area to try to find a second mate.

Scientists discovered that his song changes when he does this.

His song becomes shorter, and he repeats notes less often.

Female birds seemed to prefer songs from male birds that did not have a mate yet.

When scientists changed the bachelor songs to sound like songs of mated males, females no longer preferred them.

Scientists think shorter songs might help a male hide from his first mate, so she won't chase away the new female.

But the birds are not trying to trick anyone on purpose — their behaviour comes from nature and evolution.

So a bird's song can be a little clue about whether he already has a partner!