White-tailed Ptarmigan (Lagopus leucura)
Subspecies: Four subspecies were described between 1901 and 1939, but their validity is doubtful (Braun et al. 1993). If valid, Montana birds would be L. l. altipetens or L. l. leucura (see AOU 1957).
Status and Occurrence: Uncommon to fairly common permanent resident at and above tree line in Glacier NP, the Mission Mts., the Swan Mts., and the Flathead Range within the Bob Marshall Wilderness Complex south to at least Scapegoat Mt. One in winter plumage photographed by Bill Pomeroy on 17 Apr 1981 near Robinson Mt. is the sole report from the Purcell Mts. (see Wright 1996). Without question, more people have seen them at Logan Pass in Glacier NP than anywhere else in the state. Eggs are laid from early Jun to early Jul and hatch about 24 days after a clutch is completed; downy chicks have been observed throughout Jul, and females have been seen with older juveniles through mid-Sep. The state’s first specimen was an adult female collected on McDonald Peak in the Mission Mts. on 2 Aug 1949 (UMZM 1678; not 1 Aug as reported by Wright and Conaway 1950).
Habitat: In summer, White-tailed Ptarmigans are birds of alpine tundra and fellfields at or above tree line. They prefer terrain that is flat or gently sloping in snow-accumulation areas, often near running water and rocks. Ground cover usually consists of dwarf willows and other plants that are <30 cm high, although the birds also use patches of krummholz conifers (Choate 1963b, Scott 1982). Nests are shallow depressions on the ground, sometimes in exposed sites but often partially protected by rocks or low shrubs (Weydemeyer 1931a, Choate 1960). Winter habitat is poorly known in Montana but includes taller willow and heath above tree line and thickets of subalpine willow and aspen as snow depths increase (Choate 1963a). Willow buds and twigs are a major winter food.
Conservation: Level III Priority and Species of Concern in Montana because of its restricted range and apparent scarcity. Although its alpine habitat is largely secure, the species is vulnerable to effects of climate change, especially reduced winter snow pack and upward encroachment of tree line, which would result in lower numbers of birds and long-term loss of alpine habitat (Wang et al. 2002). White-tailed Ptarmigans are hunted in Alaska, Canada, Utah, California, and Colorado but not in Montana (Braun et al. 1993). The global population estimate is two million birds (Rich et al. 2004).
Historical Notes: The first published report from Montana was by George Bird Grinnell, who found White-tailed Ptarmigans to be common at and above tree line near St. Mary Lake in the fall of 1887. Grinnell (1888: 368) noted that they were in “full winter plumage” by 11 Nov and provided an accurate description of vocalizations: “As I walked toward them one of them walked up and down on a flat rock…and cackled shrilly, the note being exactly that of a domestic hen when frightened….The tones in their manner of utterance reminded me somewhat of one of the calls of the Sora Rail, but the notes were fuller, broader and louder.”
Florence Merriam Bailey believed that the White-tailed Ptarmigan was “One of the most interesting birds of the world” (Bailey and Bailey 1918: 139). During the summer of 1917, she searched for a nest that had been reported along the Granite Park trail in Glacier NP. Bailey failed to locate the nest but succeeded in finding a female with a brood of newly hatched chicks near Swiftcurrent Pass, her observation providing the first documented breeding record for the state. Over the next month, Bailey found broods in widely scattered locales along the Continental Divide, but no nests. Indeed, nests remained undiscovered by ornithologists until Winton and Donald Weydemeyer found a female incubating four eggs at Logan Pass on 29 Jun 1930 (Weydemeyer 1931a). Lloyd Parratt found the second known nest, also at Logan Pass, on 23 Jun 1955. It contained three eggs when discovered and four eggs when revisited a week later (Edwards 1957).
Contemporary Work: Choate (1963b) found that numbers of adult ptarmigans at Logan Pass increased each summer as a result of immigration, from 30-45 in mid-Jul to 70-80 by early Sep. The birds were closely tied to areas with short vegetation where melting snow provided moisture for plant growth, and large rocks offered protection from inclement weather and predators. Clutch sizes ranged from three to nine eggs at 10 nests, the largest clutches resulting from egg-dumping by second females (Choate 1963a). Birds followed retreating snow throughout the summer and ate new shoots of heaths and mosses until mid-Jul; buds and flowers of Salix nivalis, Claytonia lanceolata, and Ranunuculus eschscholtzii through Aug; and leaves and stems of Salix nivalis, seed heads of sedges and grasses, and leaves of Mimulus through fall.
Studying individuals captured at Logan Pass, Johnson (1968) determined that ptarmigan plumage provides great insulation but that the birds are inefficient in using evaporative cooling to lower their body temperature. In short, they are well adapted to the cold but are intolerant of high temperatures. They avoid heat stress in summer by moving to cool sites along watercourses and snow banks. Johnson and Lockner (1968) found that White-tailed Ptarmigans have the smallest ratio of heart mass to body mass of the three ptarmigan species, which is counter to expectation given that they live at high elevations. The adaptive significance of this trait (if any) is unknown.
On 22 Nov 1979, Scott (1984) photographed a White-tailed Ptarmigan in Glacier NP that had black rectrices on the left side of its tail. He suggested that the bird was either a Willow × White-tailed hybrid (albeit unlikely), or a “genetic throwback” that expressed ancestral black feathers that are typical of the other two species of ptarmigan. Regardless of the explanation for this anomaly, the point is that on rare occasions, one may encounter a White-tailed Ptarmigan that does not have a completely white tail!
Expanding on previous studies, Benson (1999) argued that ptarmigan numbers at Logan Pass are declining owing to reduced late-summer immigration and poor habitat quality, both of which have resulted from a warmer and drier climate; areas used by ptarmigans continue to be close to running water and snow, which are now less abundant than in the early 1960s. Moreover, corticosterone levels of males were elevated in late summer, which is consistent with thermal stress. Benson (2002) also showed that Logan Pass birds tended to be genetically monogamous, with only 5% of chicks and 17% of clutches resulting from extra-pair copulations.
Distribution in Montana remains of interest because ptarmigans continue to be reported from locales outside their known range. Scott (1982) surveyed 13 mountain ranges, finding ptarmigans only in Glacier NP and the Mission Mts. He concluded that only small, local populations could occur in Montana outside of these two areas. A handful of ptarmigan observations during the 1980s and 1990s from the Swan and Flathead ranges in the Bob Marshall Wilderness, including the discovery by Mike Schwitters of a female on a nest at Headquarters Pass in Jun 1988 (Wright 1996), documents their presence in areas where Scott overlooked them. Also of interest is the absence of ptarmigans in the Beartooth Range, which contains the largest expanse of alpine habitat in the state. Braun and Pattie (1969) posited that the limiting factor for ptarmigans in the Beartooths is the absence of suitable breeding habitat. Prime breeding habitat in Colorado includes tundra near Engelmann spruce-willow krummholz, and windblown areas that become snow-free early in the spring. These features are absent from the Beartooths, the krummholz there being nearly devoid of willows. In Braun and Pattie’s estimation, separation of the few windblown areas in the Beartooths from willows renders these areas unsuitable for breeding.
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Copyright Notice: © 2012. Jeff Marks, Dan Casey, Paul Hendricks.