Willow ptarmigan a range of lower plant species. It is also believed that the greening of parts of the Arctic is affecting Willow Ptarmigan populations by altering the shape and size of the shrubs they are able to feed on. Male willow ptarmigans 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
Winter white dwarf hamster sungorus sungorus". Today Winter white dwarf hamsters and Campbell's dwarf hamsters are considered separate species with the Winter white officially known as "Phodopus sungorus". The coat of the Winter white hamster is less woolly than that of Campbell's dwarf hamster, and apart from the normal colouring, they can be coloured sapphire, sapphire pearl, or normal pearl. The head length of the Winter white hamster is 70–90 mm, the length of the tail is 5–15 mm, and the hind legs are 11–15 mm. The body weight changes dramatically throughout the year. It is at its lowest during the winter. In males,