Willow ptarmigan complicated changes in plumage several times a year and the differing colour and pattern of the summer plumage: The willow ptarmigan often hybridises with the black grouse ("Tetrao tetrix") and the hazel grouse ("Tetrastes bonasia") and occasionally with the western capercaillie ("Tetrao urogallus"), the spruce grouse ("Falcipennis canadensis") and the rock ptarmigan ("Lagopus muta"). During the Pleistocene, the willow ptarmigan widely occurred in continental Europe. Authors who recognize paleosubspecies have named the Pleistocene willow ptarmigan "L. l. noaillensis" (though the older name "medius" might be the correct one). These marginally different birds are said to have gradually changed from the
Ptarmigan Pass (Sawatch Range) Ptarmigan Pass (Sawatch Range) Ptarmigan Pass (elevation 11,765 ft) is a high mountain pass in the Rocky Mountains of central Colorado in the United States. It is located on the crest of the northern end of the Sawatch Range, along the border of Eagle and Summit counties, south of Vail Pass. The pass is traversed by a jeep trail that is passable by four-wheel drive vehicles and on foot. 2WD vehicles will only make it to the summit from the west; the east side is rocky and boggy at times. The trail connects Interstate 70 east of Vail Pass with