Willow Grouse - Behaviour

Behaviour

Male Willow Ptarmigan's are territorial birds. Males arrive in the breeding areas and set up territories in April and May, aggressively defending them against male interlopers. When the females arrive a few weeks later, the male performs courtship displays such as aerial manoeuvres, strutting and tail-fanning. When she has chosen a mate and a nesting site, the female lays a clutch of six to ten eggs in a shallow depression in the ground. The nest site is usually in a hidden location at the edge of a clearing.

A small minority of male Willow Ptarmigan are polygynous but most are monogamous. They are assiduous at guarding both nest and mate, particularly early in the incubation period and when the eggs are nearly ready to hatch. During this time, the greatest danger may be from conspecifics. In most other species of grouse, only the female takes care of the young, but the male Willow Ptarmigan also helps with feeding the brood and protecting them. He may take over completely if the female dies. In particular, the male defends the young from predators and both he and his mate can dive-bomb intruders or lure attackers away by pretending to have a broken wing. Nevertheless, the chicks face many dangers which range from attacks by foxes or birds of prey, getting separated from the rest of the brood, bad weather and coccidiosis. Fewer than 35% of chicks survive to eleven months and only a minority of these reach maturity. Despite this, in favourable seasons, many juveniles may survive and the population of Willow Ptarmigan is prone to wide fluctuations in size.

Willow Ptarmigans are hardy vegetarian birds, but insects are also taken by the hatchling young. The main diet of the adults at all times of year is willow, with leaves being eaten in summer and buds, twigs and catkins supplying the main nutritional needs in winter and early spring. Berries also form part of the diet when available. By September, families begin to form flocks. The females and young migrate to lower altitudes and may overwinter 100 miles (160 km) from their breeding grounds in wooded valleys and hilly country. The males also congregate in small groups but do not usually travel as far as the females.

Widespread and not uncommon in its remote habitat, the Willow Ptarmigan is classified as a species of "Least Concern" by the IUCN. This is because, even if, as is suspected, numbers are declining slightly, it has a very wide range with a total population estimated at forty million individuals.

• Adult female in summer plumage, Trollheimen (Norway)

• Adult female in summer plumage, near Saranpaul in the northeast Urals (Beryozovsky District, Khanty-Mansi Autonomous Okrug, Russia)

• Adult male L. l. alascensis in autumn plumage, Lake Clark National Park (Alaska, USA)

• Adult male in summer plumage, Denali National Park and Preserve (Alaska, USA)

• Juvenile, Denali National Park and Preserve (Alaska, USA)