Common loons defend breeding territories on fresh water lakes in
the northern US and Canada. While a great deal is known in
general about their breeding biology it was the advent of
banding that enabled identification of individual loons. Cornell
professor of neurobiology and behavior Charles Walcott and
colleagues Walter Piper and Jay Mager have been studying a
banded population of loons near Rhinelander, WI for the past 18
years. They have found that loons are quite faithful to the
lakes on which they breed returning for an average of 5 years.
Loons looking for a breeding site will either pick a vacant
lake, replace a missing breeder or actively displace a pair
member. Female fights are relatively benign with the winner
taking over the territory and the resident male, the loser
moving to another lake in the vicinity. For males, fights are
more serious; in 30% of such fights a male is killed. And if a
male is killed it is always the resident, never the intruder.