April 15 2009

12:00 LSB 2320

Charles Walcott
Dept. of Neurobiology & Behavior, Cornell University

Loony Tunes and Fatal Fighting: The breeding Ecology of the Common Loon


Common Loons, Gavia immer, establish breeding territories on fresh water lakes. Territories can be founded on vacant lakes, by replacing a missing pair member or by actively evicting a member of a pair. When an intruding female takes over a territory, the displaced female moves to an adjacent lake. In contrast, when the intruder is a male. About 30% of the territorial battles are fatal. If a loon is killed, it is always the resident male, never the intruder. We don't know why there is this asymmetry in the behavior of the two sexes. But since it is the male loon that seems to select the nest site with improving reproductive success every year, this may be the reason. Vocalizations, especially the male "yodel", play a role in territorial defense. Only the male gives a yodel, usually in response to the potential intrusion of another male. Each male has his own characteristic yodel that is stable from year to year. If, however, a male changes territory, it changes its yodel. And it always changes it to increase the difference between its former yodel and that of the previous resident of the territory. In addition to individuality, the pitch of the yodel reflects the mass and physical condition of the loon, and the lengthy of the yodel its willingness to fight.











































































































































































































































































































































































































































































































































































































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