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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Page 93 of 139

N O R T H A M E R I C A N B I R D S 268 C O LO R A D O & W YO M I N G Boulder, Logan, Prowers, and Yuma. Sage Thrasher is typically spread very thinly over se. Colorado in winter, so the count of 15 from Pueblo Reservoir 20 Dec (DT) was un - precedented. The prairie-breeding longspurs are typically found wintering in the Region only in the very se. corner of Colorado, so the 2-4 Chestnut-collareds 4-11 Jan and one McCown's 4-5 Jan near Dear Trail (G. Rutherford) provided just the second winter Arapahoe record for each. Of three Wyoming Snow Bunting reports, the highlight was the 100 were near Jackson Hole (fide SP), where considered rare, although the species may be annual on the National Elk Refuge and along the w. slope of the Tetons (SP). TOWHEES THROUGH FINCHES Green-tailed Towhee is quite rare in winter in Colorado, so one in the nw. quadrant of the state at Steamboat Springs, Routt 18-20 Dec (P. Rice, ph. TM) was surprising, while one at Frederick Reservoir, Weld 25 Dec (ph. SGM) was slightly less so. A Spotted Towhee w. of Cheyenne, Laramie 29 Dec–3 Jan (S. Campagnaro) was about Wyoming's twenty- fifth in winter. Also surprising was the zero eBird records of Chipping Sparrow from Colorado this season. There were only single reports of Field Sparrow in Yuma 27 Dec (MP, Animas records. The first of three Mountain Bluebird re - ports from Wyoming, where rare in winter, came from the Lyman Rest Area, Uinta 26 Dec (J. Knopf), where the flock of 20 provided a nice sight and a new state winter eBird maxi - mum. The others were of 5 at Riverton, Fremont 27 Dec (DJ, EC, JM), which added to about a dozen previous C.B.C. reports, and a single at Green River, Sweetwater 7 Feb (J. Kendall), the date of which approached spring-arrival timing. Bucking the recent trend of increasing winter occurrence, just 3 Hermit Thrushes were found in Colorado, singles in Pueblo 23 Dec (G. Nikolai), La Plata 7-17 Jan (RMo), and Mesa 11 Jan (R. Lambeth). Colorado hosted a Varied Thrush in El Paso 2-4 Dec (D. Rudin) and another in Park 2 Dec (DS); the species was recently removed from the state review list. Although Gray Catbirds are occa - sional in Wyoming into Dec, one at Lucerne, Hot Springs 24 Feb (SH) was quite unusual and provided Wyoming's first winter record in about five years. The Colorado mimid show was subdued this season but high - lighted by a relatively large number of Brown Thrashers, with 2 in Baca and singles in Bent, snow melt in Sweetwater, a massive move- ment carefully estimated at around 8250 birds took place 5 Jan at Seedskadee (TK) for a record Wyoming eBird tally and possibly a new state maximum. A Tree Swallow 15 Feb in Boulder (CK) was seasonally nearly unprec - edented in the Region, especially for the date! Mountain Chickadees were noted well off the mountains in Adams, Arapahoe, Morgan, Otero, and at four Weld sites. A Black-capped Chickadee x Mountain Chickadee hybrid in Denver 27 Dec (A. Hudak) added yet another report to the recent spate, most of which orig - inate from the Denver-Boulder metro area. The shape of Wyoming winter abundance of Red-breasted Nuthatch has that value de - clining from 0.385 per eBird checklist in Dec through Jan (0.268) and Feb (0.251), but this season's abundance was quite elevated, par - ticularly in Dec, as evidenced by the monthly values of 0.531, 0.348, and 0.268. Although Pygmy Nuthatch is considered very rare in the Black Hills region, it seems that a more accurate description is that it is resident in a very specific elevational habitat band that encircles the Black Hills (D. Ward). A Crook private residence within that band hosted 4-7 birds all winter (KC), as it seems to do year-round. Outside of that habitat band was a group of 7 at Keyhole Reservoir, Crook 28 Dec (J. Adams). Wyoming has about 25 winter reports for Marsh Wren, with the two this season being singles at Seedskadee 2-17 Feb (TK) and at Ocean Lake, Fremont 28 Feb (DN). Winter Wrens were noted in nine e. Colorado coun - ties, with singles found in neighboring Carrizo Canyon and Cottonwood Canyon, sw. Baca 10 Dec (DAL, JT). American Dipper has been regular in sw. Adams (a plains county) in winter for a while now, so it may not seem odd that sw. Arapahoe got into the action this winter, with 1-2 at South Platte Park 1-12 Jan (F. Farrell) providing a first county record. Another provided Wyoming's second plains record at Hereford Ranch 3-4 Jan (ph. CSe). Eastern Bluebird is regular in winter as far s. and w. as Pueblo and Fremont, but the 2 at Trinidad Reservoir 11 Dec (RMi) provided the westernmost of very few Las SA Pine Siskin distribution was, even for this peripatetic species, seemingly anomalous. The species is typically widespread, sometimes abundant, in montane Colorado in winter. The average pattern of eBird frequency there is 8-9% during Dec, a nadir of 5.5- 6.5% in Jan, and a seasonal peak around 13% in Feb, the last possibly due to migration. This winter, the shape of the graph was similar, but much more extreme, with Dec and Feb frequencies peaking at 12% and nearly 20%, respectively. However, the mid-winter Jan nadir was truly that, with frequency hovering around 2% in the first three weeks, but climbing to 4.4% in the last week. On the Plains, the frequency pattern is quite similar to that of montane Colorado, but at lower amplitude (Dec peak of 6.7%, Jan trough of 3.0%, and Feb peak of 7.3%). The respective values from this season were 5.2%, 1.2%, and 3.9%. (Frequency derived from eBird data from the roughly 15 most heavily birded montane and 15 most heavily birded Plains counties, respectively.) In the e. foothill-edge counties, which combine montane and Plains aspects, the fre - quency shows the same peak-valley-peak shape but with the amplitude tamped way down; essentially a hybrid of the montane and Plains graphs: 11.3%, 7.1%, and 10.7%. The winter 2014-2015 graph, with the exception of a last-week-of-Dec spike to 16%, varied little: 6.6-8.5% in the rest of Dec, 5.0-6.7% in Jan, and 5.2-6.9% in Feb, except for a the third- week spike to 8.9%. (Frequency was derived from eBird data from the 9 e. foothill-edge counties, plus Broomfield, Denver, and Fremont.) However, the oddest aspect of Pine Siskin occurrence this season was the geographic distribution on the Plains. East of the foothills, the species was stuck to the urban corridor, with virtually all reports coming from w. of a line drawn between Greeley and Pueblo, ex - cept that siskins were noted the length of the Arkansas River e. to Kansas. This distribution may suggest that most siskins on the Plains had dropped out of montane Colorado, rather than coming from points to the north. We encourage readers to explore influxes of this and other species in the eBird output tools, both the graphs and the maps. This immature male Indigo Bunting found near Rocky Ford, Otero County 15 De- cember 2014 provided just the second winter record from Colorado. Ageing Indigo Buntings in the field in winter can be tricky, but other images of this bird show drab primary coverts lacking blue edges. Photo- graph by Duane Nelson.

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