gREATER sCAUP (Aythya marila)
The colloquial term for scaup, “bluebill,” was coined by wildfowlers who hunted over deep-water decoys in the Atlantic Flyway. Conventional wisdom held that Greater Scaup, being the more coastal of the two scaup species, would not be expected in Montana. Indeed, most Greater Scaup migrate and winter along seacoasts, and some of the earlier Montana reports may have been dismissed as coming from people who were inexperienced in separating them from the highly similar Lesser Scaup. As it turns out, however, Greater Scaup regularly occur inland on freshwater lakes and large rivers in the n. interior of the U.S. They breed in the Old World from Iceland and Scandinavia east across n. Siberia to Kamchatka. Their breeding range in the New World is more restricted, occurring from the Aleutian Is. and Alaska Peninsula across n. Alaska and then patchily from n. Yukon Territory to the Ungava Peninsula and Gulf of St. Lawrence; isolated breeding has occurred in the s. prairie provinces of Canada (Kessel et al. 2002).
Subspecies: A. m. nearctica
Status and Occurrence: Considered rare until the early 1980s, but now known to be a fairly common to locally abundant migrant and winter visitor. Most sightings are from reservoirs on the Missouri R. near Helena and Great Falls west to Flathead Lake, although sightings are scattered eastward to the Tongue R., lower Yellowstone R., and Fort Peck. Hundreds occur during migration at Church Slough, an oxbow of the Flathead R. near Kalispell, where they outnumber Lesser Scaup in Mar and Apr (D. Casey, pers. obs.). They are also the most common scaup in winter, with hundreds in mixed flocks of diving ducks on Flathead Lake at Dayton and in Kalispell Bay between Bigfork and Somers. The earliest specimen is a female mounted by Kalispell taxidermist Harry Wilson on or before 1946 and probably taken on Flathead Lake (UMZM 7797; Hoffman and Hand 1962). Two others are females from near Ronan, 13 Oct 1975 (UMZM 15957), and near Dixon, 3 Dec 1977 (UMZM 16254).
The Bigfork CBC recorded an average of 99 (max. 548) Greater Scaup from 1989-2007. They were reported 13 times on four other CBCs during that period (Great Falls, Libby, Ninepipe NWR, and Livingston), with a high count of 30 in Livingston in 1993. The species is much rarer during the late spring and summer months, but pairs have been seen twice in w. Montana in June: Georgetown Lake, 28 Jun 1993, by Ed Harper (AB 47:1129); and near Browning, 15 Jun 1993, by Dan Casey. The nearest breeding areas are in s. Alberta, although all records are from the early 1900s (Kessel et al. 2002).
Habitat: The species forages almost exclusively in the shallower bays and edges of large lakes and major rivers such as the Flathead, Clark Fork, and Missouri, feeding opportunistically on submerged plants, mollusks, and crustaceans (Kessel et al. 2002). To a lesser extent, it also uses smaller shallow wetlands west of the Continental Divide and along the Rocky Mountain Front (e.g., Freezout Lake).
Conservation: At the continental scale, the Greater Scaup has been classified as “Moderate” priority in the 2004 North American Waterfowl Management Plan; the population estimate for North America is 800,000 birds. Conservation efforts have focused on protecting and restoring key coastal wintering areas.
Each of the three Joint Ventures that overlay Montana has committed to protecting and restoring critical wetland habitats that serve as breeding, migration, and wintering areas for waterfowl. ABC is working with the Intermountain West Joint Venture to document the importance of w. Montana wetlands to this and other priority waterfowl species and to protect key sites that have been identified.
Historical Notes: Scaup were known as “black heads” in the 19th century. Elliott Coues (1874b: 573) clearly had difficulty separating the two species, stating that “I frequently saw Black heads in Dakota and Montana, especially during the migrations, but whether this species [Greater] was with the succeeding [Lesser] was not determined.” The earliest sight record for Montana was by George Bird Grinnell (1868: 368), who noted that they were “Abundant on the lower St. Mary’s Lake [Glacier Co.] late in October, 1887.” Within Glacier NP, Vernon Bailey found them “scattered over Lake McDonald from one end to the other in both large and small flocks, aggregating at least hundreds” on 21 Apr 1918 (Bailey and Bailey 1918: 121). Saunders (1921: 173) placed the species on his hypothetical list, noting “While I do not doubt that this species occurs as a migrant in Montana, all the records based on specimens prove to be M. affinis, and the two species are too nearly alike to admit one to the list on sight identification only.”
Contemporary Work: In 2008, ABC surveys documented that Church Slough supported a minimum of 6,962 use days by this species in March (out of a total of 52,356 waterfowl use days at the site). Knowledge about the distribution and status of Greater Scaup in Montana will increase as more observers become skilled at separating the two species of scaup in the field.
Copyright Notice: © 2008. Jeffrey S. Marks. All Rights Reserved