White-tailed ptarmigan and willow ptarmigan are two species of ptarmigan that live in northern regions. Ptarmigans are medium-sized birds in the grouse family. They are the only bird species that stay in northern mountainous areas year-round. Both white-tailed ptarmigan and willow ptarmigan have feathers that change color to camouflage with the seasons. In winter, their plumage turns completely white as camouflage against the snow. However, there are some key differences between these two ptarmigan species in terms of their physical characteristics, habitat, distribution, diet, breeding, and conservation status.
Physical Characteristics
The most noticeable physical difference between white-tailed ptarmigan and willow ptarmigan is in their plumage.
Plumage
In summer, white-tailed ptarmigans have reddish-brown plumage on their head, neck, breast, back, and wings. Their bellies are white. As their name suggests, these birds have a distinctive white tail year-round.
Willow ptarmigans have feathering that varies from brown to grey in summer. Their bellies are also white, but their tails remain brown/grey all year.
Size
White-tailed ptarmigans are slightly larger than willow ptarmigans. White-tailed ptarmigans reach lengths of 13-16 inches compared to 11-15 inches for willow ptarmigans.
Weight
White-tailed ptarmigans are also heavier than willow ptarmigans. White-tailed ptarmigans weigh 1-1.25 lbs compared to 0.75-1.1 lbs for willow ptarmigans.
Habitat
White-tailed ptarmigans and willow ptarmigans live in different alpine habitat types:
White-tailed Ptarmigan Habitat
White-tailed ptarmigans inhabit rocky mountainsides and ridgelines above treeline. They tend to live at higher elevations than willow ptarmigans.
Willow Ptarmigan Habitat
Willow ptarmigans prefer lower elevations in willow thickets and shrubby vegetation. They are often found in valley bottoms and wet meadows.
Distribution
White-tailed ptarmigans and willow ptarmigans have overlapping but different distributions:
White-tailed Ptarmigan Distribution
White-tailed ptarmigans are found along the mountainous spine of western North America from British Columbia to New Mexico. Their range extends as far east as South Dakota.
Willow Ptarmigan Distribution
Willow ptarmigans have a more northerly distribution than white-tailed ptarmigans. They are found throughout Alaska, Canada, and the northernmost parts of the contiguous United States. Their range extends farther north into the Arctic tundra.
Diet
Both white-tailed ptarmigans and willow ptarmigans are herbivorous, but they consume slightly different plant material:
White-tailed Ptarmigan Diet
In the summer, white-tailed ptarmigans eat buds, leaves, flowers, and seeds of alpine plants including dwarf willow, avens, saxifrages, and heathers. In winter, they switch to eating willow and birch buds and catkins.
Willow Ptarmigan Diet
Willow ptarmigans aptly get their name from eating mostly willow buds and twigs year-round. They also consume other shrubs, herbs, and berries from the valleys and tundra where they live.
Breeding
White-tailed ptarmigans and willow ptarmigans both have similar breeding behaviors, but on different schedules:
White-tailed Ptarmigan Breeding
White-tailed ptarmigans breed earlier in the spring once the snow melts in their rocky mountain habitat. Males begin displaying for females in late April or May. Females lay 6-8 eggs in nests on the ground in May to June. Hatching starts in June and chicks fledge in early July.
Willow Ptarmigan Breeding
Since willow ptarmigans live farther north, they breed later in the summer as the snow melts in their Arctic habitat. Males display for females starting in May. Females lay 5-10 eggs in nests on the ground in June. Chicks hatch in July and fledge in August.
Conservation Status
While both ptarmigan species have declined in numbers due to habitat loss, white-tailed ptarmigans are more threatened:
White-tailed Ptarmigan Conservation Status
White-tailed ptarmigans are listed as Near Threatened on the IUCN Red List. Climate change has caused their alpine habitat to decline. Other threats include human recreation disturbance and predators.
Willow Ptarmigan Conservation Status
Willow ptarmigans are still listed as Least Concern on the IUCN Red List. Their Arctic habitat has remained relatively intact so far. But climate change may threaten their habitat in the future.
Key Differences Summary
Character | White-tailed Ptarmigan | Willow Ptarmigan |
---|---|---|
Summer Plumage | Reddish-brown head, neck, breast, back, and wings; white belly and tail | Brown to grey overall plumage; white belly |
Size | 13-16 inches long | 11-15 inches long |
Weight | 1-1.25 lbs | 0.75-1.1 lbs |
Habitat | Rocky mountainsides and ridgelines above treeline | Willow thickets and shrubby vegetation at lower elevations |
Range | Western North America mountain spine | Northern North America and Arctic tundra |
Diet | Alpine plant buds, leaves, flowers, and seeds | Willow buds and twigs, other shrubs and herbs |
Breeding Season | Late April to July | May to August |
Conservation Status | Near Threatened | Least Concern |
Conclusion
In summary, while white-tailed ptarmigans and willow ptarmigans are both northern grouse that turn white in winter, they differ significantly in their size, exact plumage, habitat preferences, range, diet, breeding season, and conservation status. Knowing how to distinguish these two species is important for bird identification and understanding their distinct ecology in the alpine and Arctic regions they inhabit. Their differences highlight the diversity of northern bird life.