During the long, dark polar winter, all birds leave Spitsbergen for more southern, warmer area’s with more sunlight. Some of them, like the Ivory or Glaucous Gull, stay nearby and only follow the edge of the pack ice, while others fly all the way to Antarctica, like the Arctic Tern. There is, however, one birdspecies that stays on the archipelago year round: the Spitsbergen Ptarmigan. They do move around a little, spending more time on the tundra in summer and on the higher, windswept ridges in winter, but they never leave the archipelago.
The Spitsbergen Ptarmigan is a subspecies of the Rock Ptarmigan and is endemic to Spitsbergen. They are slightly larger and heavier as the Rock Ptarmigans on Scandinavia, but I doubt you’ll notice as you are highly unlikely to ever see them together. In winter they are pure white (though they do get a bit dirty at times). In summer they get a brownish colour, which blends in perfectly with the tundra although the males keep at least some of their white feathers until quite late in the season.
This means that the beginning of summer (around June) is the easiest time to find Ptarmigans. Especially the males stick out on the already green tundra with their white feathers. And this is also mating time, making them much more focal. Later in the season, in July and August, they can be notoriously difficult to find. Sometimes you only notice them when you’re only a few meters away from them. When you have found them, they can be really tame, giving great opportunities to take pictures.