And each male, as ornithologists' recordings reveal, has a slightly different version of the song. The danger call, the tremolo, sounds like a crazed human laugh and is the only call used both during flight and on water. Although loons prefer to avoid danger by diving underwater and resurfacing a safe distance away, they will defend their territory. If the tremolo doesn't warn intruders away, loons stand on the water by violently kicking their feet and flapping their wings. If the defensive penguin-dance doesn't work, loons may attack intruders by either flapping their wings and running across the water or by diving underwater and pecking interlopers with their sharp bills.
Loons spend most of their time in the open water.
They can be seen stretching their wings after a dive, rolling over on their backs and waggling one foot, or dozing with their heads resting on their backs. When they aren't preening or resting, they swim and feed with their heads underwater, peering for fish hiding under rocks, lily pads, or reeds. They, like grebes and auks, are diving birds. Their red eyes filter out the yellow, orange, and red light underwater, making locating and pursuing fish easier. And their daggerlike bills are excellent for grabbing and eating small trout, minnows, bluegill, smelt, and crappies.