Incubation typically lasts 21 days, and the downy chicks are able to leave the nest within a day of hatching. The female tends her young, but they feed themselves, and are able to fly at about 10 days. Chicks are independent at 10 to 12 weeks old. Behavior The Rock Ptarmigan may migrate short distances, leaving highland nesting ground behind in winter and flying southward in flocks toward lowland wintering grounds, but it does not leave the tundra. Sexes separate during winter, forming single sex groups.
Flocks disassemble in early spring.
At that time males choose and vigorously defend large territories. High speed aerial chases with much vocalization are common when territory is threatened. The territory display includes elaborate song flights. These begin with the male leaping into the air and flapping. He then flies vertically until he reaches stalling speed, at which point he spreads his tail and parachutes to the ground, making a gutteral, staccato call.