If you're walking in the woods, you're probably going to get more annoyed by a loud, screeching bird call than a soft, complex birdsong. But dark-eyed juncos are just the opposite. These birds will find and fight their soft-singing peers.
Now, lest we think of dark-eyed juncos as simply the philistines of the animal kingdom who go about brawling with any bird that inject a little creativity into its birdsong - which, I'll admit, is a most entertaining thought - there's a more straightforward logic at play here. As with most things, it's all about mating and reproduction.
Males juncos will let out a loud, boisterous call when they're asserting their territory, but they'll favor a softer, more melodic song when they're trying to attract a mate. Researchers at Indiana University found that, when they played these two different songs for some male juncos, the birds completely ignored the loud song but actively searched for whoever was making the softer call.
In the wild, any male junco that goes hunting for the fellow junco behind that song is basically looking for a fight. It appears the birds are far more interested in maintaining their access to potential mates than they are protecting their territorial claims. They may not be philistines, then, but it does appear the juncos care far more about sex than land...which I suppose, as these things go, it's a fairly sensible decision.
Lead researcher Dustin Reichard explains:
"Communication researchers have long argued that whispered, low-amplitude songs are produced at a low volume to avoid being heard by eavesdroppers. What we have shown in juncos is that males who are overheard singing short-range song in their neighbor's territory will likely evoke a very aggressive response from the territory owner, making it very advantageous to be quiet.
"Low-amplitude songs are far more common among songbirds and other animals than most people realize. Our knowledge of low-amplitude songs has been improving in recent years and will continue to expand with technological advances in our recording abilities and renewed interest in what function these enigmatic signals serve."