North American Birds

VOLUME 69 NO2 2016

A Quarterly Journal of Ornithological Record Published by the American Birding Association. The mission of the journal is to provide a complete overview of the changing panorama of our continent’s birdlife.

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V O L U M E 6 9 ( 2 0 1 6 ) • N U M B E R 2 265 C O LO R A D O & W YO M I N G was stellar: singles at Gray Reef Reservoir, Natrona 6 Dec (ZH) and at Jackson, Teton 11- 19 Dec (C. Boeh, H. Cadwaladar) and duos at Seedskadee 8 Dec (TK) and Table Mountain 7 Dec (SB, LM). Although Redheads typically return to Wyoming in Feb, it is usually not until Mar that their numbers swell. This win - ter saw the increase begin a few weeks early, with unusually large Redhead concentra - tions, mostly in Albany, by late Feb (m.ob.); Ring-necked Ducks and Lesser Scaup simi - larly swept into Wyoming in unusually large numbers for late Feb. Greater Scaup has been found to be regular in Colorado in winter in small numbers, with reports this season from 14 e. and montane counties, with the South Platte Park, Arapahoe flock size max - ing at 21 (m.ob.). Adding to just a handful of Wyoming winter reports, 2 Greater Scaup visited Gray Reef 6 Dec (ZH). Scoters are ex - pected in Colorado mid-Oct through Nov but are less expected as late as Dec, with Surf being the most numerous species. Thus early Dec scoters are mostly Surf, such as the 2 at Colorado Springs through 6 Dec (m.ob.); the Surf Scoter at Cañon City 13 Dec (ph. DA) was late. However, reports of 1-2 White- winged Scoters were scattered across four e. counties, with the single at Pueblo Reservoir 29 Dec–8 Feb (BKP) accounting for the only post-Christmas scoter occurrence. Black Scoters, the rarest of the lot, were noted 5 Dec at Colorado Springs (one; DA) and 2 of the 3 noted at Rifle Gap Reservoir, Garfield (m.ob.) from fall lingered through at least 13 Dec (S. Riffe), the latter site being on the West Slope, for which there are only about 20 antecedent records. Single Long-tailed Ducks visited two sites w. of the Plains, where rare, particularly in winter; one in Park, the SA Due primarily to the relatively short time that birders have paid attention to Cackling Goose, we are all still working out the identification, distribution, abundance, and migration timing of some subspecies. Richardson's Cackling Goose (B. h. hutchinsii), with its quite extensive swath of occurrence in the United States and Canada, is of particular interest in the Region. The second edition of the National Geographic Society's Complete Birds of North America (2014) presents a map of its distribution, indicating regular winter occurrence in numbers from the n. Colorado plains eastward through Kansas and Missouri to cen. Illinois, southward through the panhandle of Texas, Oklahoma, and Arkansas, with a disjunct area centered on the Texas coastal bend. Winter Cackling Goose frequency and abundance differ greatly across the two major river systems on Colorado's plains (South Platte, Arkansas), despite the two rivers being just 130-320 km apart. The northerly drainage (South Platte), which defines the n. edge of the subspecies' regular winter range, hosts much greater numbers than does the s. drain - age. Frequency, as determined by eBird checklists, peaks in e. Colorado in the last week of Nov and declines to approximate stasis in late Dec–Jan (12-13% of checklists in the South Platte, 7-8% in the Arkansas). The shapes of abundance graphs of the two drainages are roughly similar, though with South Platte values roughly 12-15 times greater than those of the Arkansas. The lion's share of this difference may well be due to the greater abundance of parks, golf courses, and water bodies in n. Colorado. Despite its abundance in e. Colorado, Cackling Goose is surprisingly rare in w. Colorado (where the Richardson's:Taverner's ratio has yet to be ascertained), so of interest were occurrences at Craig, Moffat 2 Dec (FL); near Durango 27 Jan (JDB); and three times in the San Luis Valley: in Conejos 2 Dec, Saguache 25 Jan, and Rio Grande 7 Feb (DD). Taverner's Cackling Geese were noted on the nw. plains in six counties 7 Dec–9 Feb (SGM, CSh, TF), while a Ridgway's Cackling Goose (B. h . minima ) at Denver 23-31 Jan (†CSh) provides only the second Colorado record. Further evidence of the rapidly increasing winter Wyoming presence of Cackling Goose involved multiple reports from the expected se. counties, including a record tally of 1100 at Table Mountain 7 Feb (SB, LM). Hybrid geese involving Cackling Goose are rarely reported except in Colorado. The state tallied at least nine records of Snow Goose x Cackling Goose hybrids (possibly as many as 12 birds) in seven Denver Metro-area counties. Single Ross's Goose x Cackling Goose hybrids were noted in Larimer 24 Dec (NK, O. Komar, K. Pals), Adams 22 Jan (NM), and Weld 13-14 Feb (SGM, DW, GD), while 2 Greater White-fronted Goose x Cackling Goose hybrids were found in Arapahoe 8 Dec (CSh), and singles were tallied in Denver 18 Dec (NM) and Weld 25 Dec (SGM). WATERFOWL THROUGH HERONS Providing just Wyoming's fifth winter report of Greater White-fronted Goose was a single bird at the site of last winter's report, Warren A.F.B., Albany 18 Dec (MG). The species is somewhat rare in e. Colorado but quite rare on the West Slope outside of a few favored locations in Delta and Mesa, making the rela - tively large number (8-10) noted at Montrose, Montrose 10-24 Jan (JH, B. Harris) and the 2 near Durango, La Plata 8-16 Feb (JDB) of in - terest. As is typical, five-digit counts (14,000 to 40,000) of Snow Geese were restricted to the lower Arkansas River until mid-Feb, with the first big hit of presumed northbound migrants (35,000) seen at Jumbo Reservoir, Logan 15 Feb (SGM, DD, B. Tweit). Ross's Geese at Seedskadee 17-28 Feb (2-3; TK) and Table Mountain 7 Feb (6; SB, LM) provided Wyoming's third and fourth winter reports. Pueblo hogged the Colorado Trumpeter Swans away from the nw. corner (where the species is regular), with well-birded Chico's first 1 Dec (imm.; ph. JD) and an ad. at Pueblo Reservoir 24-25 Jan (MP, BS, DT). Making a very rare Feb appearance was Wyoming's sole winter Tundra Swan at Seedskadee 17- 24 Feb (TK). Wood Ducks were present at their now-annual Wyoming wintering lo - cales at Lander 8 Dec–2 Feb (7; JA, DN) and Riverton all season (3; T. Axthelm), both Fremont, while one at Casper, Natrona 21 Dec (fide CM) and 2 in Hot Springs 24 Feb (SH) were unexpected. A male Eurasian Wigeon at Cañon City, Fremont 25 Jan (JD, C. Thompson-Kolbe) was the Regional duck of the season. After nine accepted records in the 1990s, the C.B.R.C. has accepted just two more recent American Black Duck re - cords, one each in 2002 and 2012, so one at Windsor Reservoir, Weld 13 Feb (†SGM, DW, GD) was of interest. A Mallard flock estimat - ed at 2500 birds at Hudson, Fremont 1 Feb (SB, ph. LM) tied a Wyoming eBird record tally (all others are under 1000). The spring's first Cinnamon Teal was a week or two early at Walden Ponds, Boulder 3 Feb (K. Gaherty). Though present in winter in large numbers in Utah's Great Salt Lake basin and in Colorado's urban corridor, Northern Shoveler is rare in Wyoming, particularly in Feb. Adding to just seven prior Feb eBird reports (only three away from Cheyenne) were 2 shovelers at Blake's Pond, Albany 18 Feb (ph. VS) and one at Seedskadee 21 Feb (M. Adams). A female Canvasback x Redhead hybrid at Erie Reservoir, Boulder 4 Feb (SGM) was the fanciest of the seven hybrid duck combina - tions reported from Colorado this season. Canvasback is rarely reported in Wyoming in winter, almost annually, so this winter's show

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