Vireo swainsoni brewsteri
Status: Uncommon regular spring and fall migrant west. Uncommon regular breeder west.
Documentation: Specimen: UNSM ZM6788, 23 May 1900 Monroe Canyon, Sioux Co (brewsteri) (Bruner, handwritten annotation in his copy of Bruner 1896 in possession of WRS).
Taxonomy: AOS split the former Warbling Vireo into two species based on a proposal by Cicero (2025) noting the two groups differ in several ways including morphology, genetics, song, molt, migration, and response to brood parasitism (Chesser et al 2025).
Four subspecies are recognized (AviList 2025), two of which occur north of Mexico: swainsonii, from southeast Alaska to southern Northwest Territories south to California, and brewsteri, from southern Idaho and western South Dakota south to Arizona and southwest Texas.
Nebraska birds are brewsteri (see above).
There is minimal overlap in breeding season ranges of Eastern Warbling-Vireo and Western Warbling-Vireos in Nebraska; the shortest distances between them appear to be the 80 miles (125 km) from Valentine, Cherry Co to the eastern Pine Ridge and the 35 miles (60 km) from the Pine Ridge to the North Platte River Valley. Nevertheless, recordings of singing birds in the Panhandle and west-central Nebraska are needed to discern the relative breeding distributions of the two subspecies.
It is not known whether Eastern Warbling-Vireos and Western-Warbling-Vireos hybridize in Nebraska.
Spring: May 8, 8, 11 <<<>>> Jun 13, 13, 14 (away from Pine Ridge)
An earlier date was 1 May 2025 Scotts Bluff Co.
Migration data indicate that western subspecies brewsteri arrives about a month later in the Panhandle than eastern gilvus. Away from the Pine Ridge, there are these later reports of presumed migrant brewsteri: one at Oliver Reservoir, Kimball Co 1 Jun 2022, 13 Jun 2022 Scottsbluff WTP, Scotts Bluff Co, four at Scotts Bluff WTP, Scotts Bluff Co 14 Jun 2021, up to four there through 13 Jun 2022, and up to four there during summer 2023 (see Summer). One was singing (compared with singing gilvus) at Ash Hollow SHP, Garden Co 9 Jun 2021.
- High counts: 11 at Chadron, Dawes Co 24 May 2022, 8 near Potter, Cheyenne Co 21 May 2022, and 7 at Lake Minatare, Scotts Bluff Co 30 May 2024.
Summer: The extent of the limited breeding range in western Nebraska not well defined; it may only breed regularly in the western Pine Ridge in Sioux and Dawes Cos. This is the breeding species of the Black Hills of South Dakota (Tallman et al 2002) and because migration extends into Jun, birds observed during that period may only be migrants. Bruner et al (1904) stated “So far it has only been found in Sioux county [sic], where it is common and breeds.” An adult Warbling Vireo, presumed to be this species, was carrying nesting material on 23 Jun 2008 and is the confirmed Sioux Co record in Mollhoff (2016). Recent mid-June to early Jul reports from well-birded sites in the western Pine Ridge such as Gilbert-Baker WMA and Sowbelly Canyon are infrequent and typically involve only 1-3 individuals. Previous high counts were seven at Box Butte Reservoir, Dawes Co 25 Jun 2023 and five at Walgren Lake, Sheridan Co 14 Jun 2023. Recent surveys in the Pine Ridge in the summer of 2025 by Jacob Cooper (personal communication) and colleagues did not find this species there; only a small number of Eastern Warbling-Vireos were detected. A statement that the taxon breeds at “Crescent Lake” (AOU 1957) has not been substantiated.
Breeding season reports of birds identified as Western Warbling-Vireos are limited to the Pine Ridge. There are eight mid-summer (15 Jun-30 Aug) records away from the Pine Ridge that might suggest either occasional breeding away from the Pine Ridge or early departure from the breeding range. Intriguingly, there were reports at Scottsbluff WTP, Scotts Bluff Co 23 Jun (song was difficult “to place” (Mlodinow, eBird.org)), 13 Jul, and 21 Jul 2023 and in 2024 23 Jun-18 Jul. Other reports are 3 Jul 2020 Box Butte Reservoir, Dawes Co, 4 Jul 2020 Pumpkin Creek, Banner Co, 13 Jul Lake Minatare, Scotts Bluff Co, 30 Jul 2019 Kiowa WMA, Scotts Bluff Co, 5 Aug 2021 Cheyenne Co, and 10 Aug 2021 Oliver Reservoir, Kimball Co.
- Breeding Phenology:
Nest building: 8 May-4 Jun
Eggs: 3-19 Jun - Nestlings: 17 Jun
Fledglings: 29 Jun-28 Jul
Fall: Aug 30, 31, 31 <<<>>> Sep 14, 15, 15 (away from Pine Ridge)
Later dates in the west are 25 Sep 2008 banded Scotts Bluff Co, 27 Sep 2021 Kimball Co, 27 Sep 2024 Kimball Co, and 1 Oct 2021 (2) Fort Robinson SP, Dawes Co.
Earlier dates are 17 Aug 2022 (4) Scotts Bluff Co, 21 Aug 2001 Kimball Co (Stephen J. Dinsmore, personal communication), and 25 Aug 2022 Sioux Co. There are scarce data on early departure dates in fall; later dates in Jul cited above (Summer) may also be of migrants.
Later dates are 20 Sep 2022 Oliver Reservoir, Kimball Co, and 29 Sep 2022 in Kimball, Kimball Co.
Five of seven warbling vireos netted at Oliver Reservoir, Kimball Co 31 Aug 2000 were Western Warbling-Vireos, and two netted there 21 Aug 2001 were also Western Warbling-Vireos (Stephen J. Dinsmore, personal communication). A Western Warbling-Vireo was photographed at Chadron SP’s banding station 3 Sep 2014 (LeFever 2014).
Images
Abbreviations
AOS: American Ornithological Society
AOU: American Ornithologists’ Union
BBS: Breeding Bird Survey
NACC: North American Classification Committee
NC: Nature Center
NNF: Nebraska National Forest
SHP: State Historical Park
SP: State Park
SRA: State Recreation Area
UNSM: University of Nebraska State Museum
WMA: Wildlife Management Area (State)
WTP: Water Treatment Plant
Literature Cited
American Ornithologists’ Union [AOU]. 1957. The AOU Check-list of North American birds, 5th ed. Port City Press, Baltimore, Maryland, USA.
American Ornithologists’ Union [AOU]. 1998. The AOU Check-list of North American birds, 7th ed. Allen Press Inc., Lawrence, Kansas, USA.
AviList Core Team, 2025. AviList: The Global Avian Checklist, v2025. https://doi.org/10.2173/avilist.v2025.
Bray, T.E. 1994. Habitat utilization by birds in a man-made forest in the Nebraska Sandhills. Master’s thesis, University of Nebraska-Omaha, Omaha, Nebraska, USA.
Bruner, L., R.H. Wolcott, and M.H. Swenk. 1904. A preliminary review of the birds of Nebraska, with synopses. Klopp and Bartlett, Omaha, Nebraska, USA.
Chesser, T.R., S.M. Billerman, K.J. Burns, C. Cicero, J.L. Dunn, B.E. Hernández-Baños, R.A. Jiménez, O. Johnson, N.A. Mason, P.C. Rasmussen. 2025. Sixty-sixth supplement to the American Ornithological Society’s Check-list of North American Birds, Ornithology, 2025. https://doi.org/10.1093/ornithology/ukaf015
Cicero, C. 2025. Treat Warbling Vireo Vireo gilvus as two species. NACC proposal 2025-C-3.
LeFever, J. 2014. Checklist S19659130: Chadron SP–Banding Station Area, Dawes County, Nebraska, US. eBird.org, accessed 4 Jun 2018.
Leukering, T., and S.G. Mlodinow. 2017. Selected Bird Subspecies of Interest in Colorado: Part 1. Colorado Birds 51: 154-169.
Ludlow, C.S. 1935. A quarter-century of bird migration records at Red Cloud, Nebraska. NBR 3: 3-25.
Mollhoff, W.J. 2001. The Nebraska Breeding Bird Atlas 1984-1989. Nebraska Ornithologists’ Union Occasional Papers No. 7. Nebraska Game and Parks Commission, Lincoln, Nebraska, USA.
Phillips, A.R. 1991. The known birds of North and Middle America. Part 2. Published by the author, Denver, Colorado, USA.
Sauer, J.R., W.A. Link, and J.E. Hines. 2020. The North American Breeding Bird Survey, Analysis Results 1966 – 2019: U.S. Geological Survey data release. https://doi.org/10.5066/P96A7675.
Sibley, C.G., and B.L. Monroe, Jr. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, Connecticut, USA.
Tallman, D.A., D.L. Swanson, and J.S. Palmer. 2002. Birds of South Dakota. Midstates/Quality Quick Print, Aberdeen, South Dakota.
Recommended Citation
Silcock, W.R., and J.G. Jorgensen. 2025. Western Warbling-Vireo (Vireo swainsoni). In Birds of Nebraska — Online. www.BirdsofNebraska.org
Birds of Nebraska – Online
Updated 17 Aug 2025