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 May, 1914 BIRDS OF NORTHERN MONTANA 127 LIST OF SPECIES Colymbus holboelli. Holboell Grebe. Migrant. Observed at Lubec, September 25-27, 1911. A carcass found at Priest Butte Lakes in the fall of 1912. Colymbus nigricollis californicus. Eared Grebe. Summer resident. Breeds commonly in sloughs that are overgrown with rushes. No nests found, but the birds were seen frequently with broods of young. Migration dates: September 4, 191], and May 1, 1912. Podilymbus podiceps. Pied-billed Grebe. Seen rarely in summer. Probably breeds with the above species. Gavia immer. Loon. Rare migrant. Observed once on Priest Butte Lake, May 26, 1912. Larus delawarensis. Ring-billed Gull. Migrant and summer resident. Adult birds are seen commonly all summer about the alkaline lakes and ponds, but 1 doubt if they breed, as I have never seen young birds until late in the fall. Fig. 40. I'UDSONIAN AND ALPINE ZONES, IN MOUNTAr'S AT HEAD OF BIRCH CREEK, TETON COUNTY, MONTANA. migration. Probably Herring Gulls and perhaps other species occur in migra- tions with this species, but no others have been positively identified. Migra- tion dates: April 16, 1912, and November 19, 1912. Larus lhiladellhia. Bonaparte Gull. A flock of these gulls was observed on an alkaline lake about ten miles from Choteau, October 31, 1912. Mergus americanus. Merganser. Observed on the Teton River near Choteau on April 16 and 17, 1912. A pair of birds seen each day. Mergus serrator. Red-breasted Merganser. Quite common along the Sun River inside the mountains, in August and September. A small flock observed near Choteau, May 23, 1912. Anas llatyrhynchos. Mallard. The most abundant duck in this region. Nests commonly all through the prairies, and is very abundant in migrations. Flocks also winter commonly on sloughs where there are warm springs that