This is Birdnode.

This bird has a problem.

The red-backed ferry ran is a tiny, perky songbird that lives in the scrublands of northern

and northeastern Australia.

It's highly territorial, both males and females vigorously defend their territory

from intruders.

The problem is that red-backed ferry runs are highly promiscuous, so it's difficult

for a male to be sure that the eggs in his nest are his own.

One way to avoid this predicament is for the male to physically challenge any rivals

who approach his territory by roughing them up.

Another way to deal with it is to sing.

Red-backed ferry ran pairs will sing a duet in order to deter rival males from intruding

on their territory.

Research published in 2016 found that the pairs that sang together had many more of their

own genetic offspring in their nests than pairs where the resident male had spent most

of his time beating up the intruder.

So for the male, aggression might not accomplish the goal of ensuring paternity, but singing

a spirited duet with a partner could.

For Birdnode, I'm Michael Stein.