North American Birds

VOLUME 68 NO4 2015

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.

Issue link: http://nab.aba.org/i/605532

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V O L U M E 6 8 ( 2 0 1 5 ) • N U M B E R 4 529 C o lo r a d o & W yo m i n g in Wyoming in summer away from the limited nw. breeding range, so quite unusual were re- ports of singles from Carmody Lake, Fremont 21-29 Jul (AG, AL) and 3 at New Fork Lakes, Sublette 28 Jul (G. Dimming). The Sands Lake, Chaffee Common Goldeneye saga continued this summer, with at least 3 (ad. male and fe- male, imm.) present through the season; what is going on here? The 5 other seasonal Com- mons in four counties (2 in Weld, singles in Larimer, Mesa, and Park) made for a large and geographically diverse Colorado summer show- ing. Breeding Barrow's Goldeneyes were noted at Echo Lake, Clear Creek (m.ob.) for the third consecutive summer; the species was previ- ously restricted as a breeder in Colorado to the Flat Tops region of the nw. quadrant. A sum- mering imm. male goldeneye in Larimer de- fed defnitive identifcation and was probably a hybrid (R. Beauchamp). Hooded Merganser has become a rare-but-regular summering bird in Colorado in the past 15 years, with scattered breeding records, but this season saw an un- precedented summer tally, with reports from six e. counties, including an unprecedented tally of 30 near Fort Collins, Larimer 18 Jul+ (ph. D. Ward et al.). Wyoming, with fewer than 20 previous summer reports, also got in on the bonanza, with 10 total at six sites in fve coun- ties from across the state. Common Loons seemed to fnd lugubrious conditions in Colorado this season, with singles in seven counties and 1-2 at Jumbo Reservoir, Logan/Sedgwick (SGM, SW), while singles in Wyoming at Seedskadee N.W.R., Sweetwater 10 Jun (T. Koerner, J. Baldwin) and Little Pied- mont Reservoir, Uinta 20 Jun (ph. MF) were away from typical nw. haunts. Clark's Grebe made an impressive showing in montane and West Slope Colorado, areas in which the spe- cies is generally scarce, with the count of 16 at Fruitgrowers Reservoir, Delta 9 Jun (J. Kellner et al.) possibly providing a record high count for w. Colorado, while hybrids were reported from Archuleta, Jackson, and Larimer. Rare and possibly diminishing as a breeder in the state, an impressive 24 Snowy Egrets at Woodruff Narrows Reservoir, Uinta 13 Jun Sa North Park, the Colorado part wholly contained within Jackson, is more like Wyoming than most of the rest of Colorado and supports, perhaps, the largest assemblage of colonially breeding waterbirds in Colorado. The four major water bodies typically have the state's largest or among the largest colonies (or, in some cases, only colony) of Eared Grebe, Western Grebe, American White Pelican, Double- crested Cormorant, Franklin's Gull, California Gull, Black Tern, and Forster's Tern. Small numbers of Clark's Grebe and moderate numbers of Black-crowned Night-Heron also breed here. Most of what recent information that we know about breeding colonial waterbirds in North Park (and elsewhere in Colorado) has been obtained over the past 15 years by Rocky Mountain Bird Observatory (R.M.B.O.) in a large efort to monitor Colorado's populations of such species that was initiated by Leukering and the late Rich Levad. Red-necked Grebe is of fairly rare occurrence in Colorado, with an average of about 4 recorded per year (most in fall); the species was re- moved from the C.B.R.C. review list only in 2002. Prior to 2014, the only summer records from the state were of single birds in Weld 2 Jun 2003 and at Lake John, Jackson 13-14 Jul 2013, the latter discovered as part of R.M.B.O.'s survey efort. The previous year's single bird became 2 birds this summer 30 May–31 Jul (CH, PS, L&LF) and proceeded to set up shop. The birds were noted building three nests and got to the incubation stage at one (ph. CH), but no young were produced. Oddly, a third ad. was noted 19 Jul (CH, PS, L&LF). Despite the lack of breeding success, these grebes still provided the Regional breeding event of the year. Except for Black-crowned Night-Heron, herons and ibises are most notable as breeders in North Park by their absence. For decades, the only consistent Regional breeding Great Egrets have occupied a single colony that was in ne. Boulder, but these moved to nearby sw. Weld in the last decade, and the Colorado occurrence pattern is strongly cen- tered on that site, with the vast majority of egrets noted in Adams, Boul- der , Larimer , and Weld . This season, R.M.B.O. located a Great Egret nest with at least 2 well-grown nestlings in the vegetation on a Walden Res- ervoir island on which California Gulls breed (ph. CH). The bulk of the state's breeding Snowy Egrets and Cattle Egrets and White-faced Ibis nest in the San Luis Valley, and the species have little his- tory of breeding in North Park, though Snowies began nesting at Walden Reservoir in 2006 in small numbers (up to fve pairs/year), and the large ibis colony at Hutton Lake is 80 km to the ne. in Wyoming. Thus, it is of note that the R.M.B.O. volunteers also noted ten nests of Snowy Egret and one of Cattle Egret this season, the latter being a frst for North Park. Though just four ibis nests were found, 120 ibis, most juvs., were present in the Walden Reservoir heronry area on 16 Aug. While all ads. specifcally identifed in Jun/Jul were White-faced, the Hutton Lake ibis colony has a history of hosting Glossy Ibis (Faulkner 2005), so we encourage careful assessment of all Plegadis in North Park. This nestling Great Egret at Lake John, Jackson County (here 17 July 2014) was one of two that were the frst such ever detected in Colorado west of eastern Boulder County. They were part of a banner breeding season for colonial waterbirds at North Park, where at least 15 species bred on the islands of various water bodies. Photograph by Chuck Hundertmark. Summer reports of Glossy Ibis in Colorado are still few and far between. This individual was at Red Lion State Wildlife Area, Logan County 12 June 2014 and was one of just six ibis at the site. This ratio strongly suggests that it is not safe to assume that all dark ibis in even a small fock are all White-faced Ibis. Photograph by Steven G. Mlodinow.

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