Transcript:

Calling All LoonsHere's a program from our archives.ambience: Loon wail callAccording to a Native American legend, this call of the loon is the woeful cry of a warrior who's been denied passage into heaven. Well, to scientists, it's the sound of one loon denying the passage of another loon to its territory. I'm Jim Metzner, and this is the Pulse of the Planet.Dave Evers is a conservation biologist with the Biodiversity Research Institute. He tells us that during the summer, adult loons compete for mating territory on the lakes of Canada and the United States. Evers: The male is searching for another loon at this point. It thinks there's a loon on its territory and an intruding loon can be very dangerous to territory holders. An intruding loon wants to get on that territory, wants to have a home. An intruding loon is a non-breeding bird that's wandering around, hoping to find a place where it can set up shop and find a mate and nest. So as an established male, he needs to find out is this intruder a dangerous bird.Without a place on the lake, the loons can't mate. And that means that by competing for territory, only the stronger birds have the opportunity to reproduce.Evers: An intruding loon coming into a territory, he's kind of testing the waters, in many ways. And he's testing to find out is there another loon there. If there is, then he has to decide, do I stay, or should I just go? And a lot of times the intruder will stay. It'll actually take part in what's called a circle dance with the pair so you have three birds in a circle, evaluating each others' fitness. The intruder loon is trying to find out: is this loon better than me? If it is, I'm going to leave. If the loon isn't as fit to be in this territory as I am, then I may have a chance to win this territory. And not just territory is at stake. Whichever loon prevails will win the resident mating partner as well. Additional funding for Pulse of the Planet has been provided by the National Science Foundation. I'm Jim Metzner.