Late Changing Plumage of Rock Ptarmigan

by Bryce W. Robinson


Male Rock Ptarmigan- Lagopus muta, still in basic plumage. June 21, 2013. Prudhoe Bay, Alaska

My exposure to Ptarmigan this past summer was not limited. Although I haven’t been able to track down the White-tailed Ptarmigan, I have had a lot of experience with both the Willow and Rock Ptarmigan.

Without hesitation I’d say that the easiest way to distinguish the two species is by call. This is very helpful in early summer, when males are traipsing around the open tundra, full of hormones, calling and chasing one another constantly. But what about later in the season, when birds are more cryptic? What about females?

The differences in plumage are subtle, and so far I feel I could only distinguish females in alternate plumage if they were side by side.

Shape is a helpful tool. Richard Crossley asked me how I distinguish between the females of the two species. My response was head shape, but he persisted and exposed my lack of confidence with the parameter. I feel like I have head shape down, but I’ll need more practice this coming summer as I chase the Gyrfalcon around the Seward Peninsula.

I chose to share the above photo as it shows a Rock Ptarmigan in late June. In late may, male Willow Ptarmigan already have full reddish necks, as they have started their pre-alternate molt. Interestingly, male Rock Ptarmigan do not begin their pre-alternate molt until early July. This makes for a simple identification tool. I’ve yet to research any answers to this difference in timing of molt between the two species. I of course, encourage any discussion on the matter.