Vireo gilvus gilvus, V. g. brewsteri
Status: Common regular spring and fall migrant statewide. Common regular breeder east and east-central, uncommon west-central and west.
Documentation: Specimens: UNSM ZM6788, 23 May 1900 Monroe Canyon, Sioux Co (brewsteri) (Bruner, handwritten annotation in his copy of Bruner 1896 in possession of WRS); UNSM ZM6789, 26 Apr 1901 Lancaster Co (gilvus).
Taxonomy: There are five subspecies, three of which occur north of Mexico (Pyle 1997): swainsonii, from southeast Alaska to southern Northwest Territories south to California, brewsteri, from southern Idaho and western South Dakota south to Arizona and southwest Texas, and gilvus, from south-central Alberta south to Louisiana and east to Maine and North Carolina. AOU (1998) places these subspecies in two groups, “western” (swainsonii) and “eastern” (gilvus); the western group includes swainsonii and brewsteri, and the eastern group gilvus. It has been suggested that the two groups may be separate species, differing “morphologically, vocally, and genetically” (Sibley and Monroe 1990, Phillips 1991, Gardali and Ballard 2020).
Two subspecies occur in Nebraska, brewsteri and gilvus. It seems clear that the breeding Warbling Vireos in the Pine Ridge are western brewsteri based on the specimen cited above and Bruner et al (1904), who stated “So far it has only been found in Sioux county [sic], where it is common and breeds.” This is the breeding subspecies of the Black Hills of South Dakota (Tallman et al 2002). A statement that it breeds at “Crescent Lake” (AOU 1957) has not been substantiated. The only records of brewsteri away from the Pine Ridge are during migration.
Eastern gilvus occupies most of the rest of the state although its western limits are uncertain. In the north, it summers west to Valentine and Merritt Reservoir SRA, Cherry Co but is rare in the western Sandhills and Panhandle away from the North Platte River Valley, with only two regular locations, the deciduous “oases” at Agate, Sioux Co and Smith Lake WMA, Sheridan Co. The only Pine Ridge reports of gilvus are at Fort Robinson SHP, Dawes Co 20 May 2015 (Rick Wright, personal communication; vocalizing) and 18 Jun 2015, possibly the same individual (eBird.org). A series of eBird reports by Steve Mlodinow and Michael Willison at various locations in the southwest sheds some light on western limits there: eastern gilvus occurred in good numbers in Dundy, Chase, Keith, and extreme southeast Garden Cos 26-27 May 2019 (eBird.org), and in 2020 Mlodinow reportd up to five at several locations in Garden, Keith, Chase, and Dundy Cos 7 Aug-4 Sep; it is known to occur commonly in the South Platte River Valley into Colorado (Leukering and Mlodinow 2017).
The above distributional information suggests that there is minimal overlap in ranges of eastern gilvus and western brewsteri Warbling Vireos in Nebraska during the breeding season; 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.
Spring: Apr 20, 20, 21 <<<>>> summer; Apr 26, 27, 27 <<<>>> summer (west); May 22, 22, 25 <<<>>> summer (brewsteri)
An earlier date is 14 Apr 2012 Dodge Co. An earlier date for brewsteri is 18 May 2018 Oliver Reservoir, Kimball Co.
Migration data indicate that western subspecies brewsteri arrives about a month later in the Panhandle than presumed eastern gilvus. Away from the Pine Ridge, brewsteri were four at Scotts Bluff WTP, Scotts Bluff Co 14 Jun 2021 and one singing (compared with singing gilvus) at Ash Hollow SHP, Garden Co 9 Jun 2021.
- High counts: 100+ at Twin Lakes, Lancaster Co, 6 May 2000, 84 at Fontenelle Forest, Sarpy Co 12 May 2018, 42 in Furnas Co 29 May 2005, and 40 at Medicine Creek Reservoir, Frontier Co 27 May 2001.
Summer: Data from BBS routes and eBird show that Warbling Vireos breed statewide, with somewhat lower densities in the Panhandle and the western Sandhills. BBS trend analysis shows an average annual increase of 1.11% (95% C.I.; 0.03, 3.21) statewide 1966-2013. Breeding season reports of birds identified as western brewsteri are limited to the Pine Ridge; birds identified as eastern gilvus document occurrence west to the Valentine area in Cherry Co in the north and Keith Co in the south, with few reports in the intervening Sandhills (eBird.org, accessed March 2018). Bray (1994) stated that the species was not known to breed at NNF Halsey, Thomas Co, where it was a migrant only, although there are more recent records indicating that it occurs there during the breeding season. Eastern gilvus breeds from Keith Co along the South Platte River Valley well into the eastern plains of Colorado, where it occurs in riparian cottonwood/willow habitat (eBird.org; Leukering and Mlodinow 2017). Two gilvus were at Lake Ogallala, Keith Co 24 Jul 2016 and one was “told by song” near Ogallala, Keith Co 15 Jun 2017.
- Breeding Phenology:
Nest building: 8 May-4 Jun
Eggs: 3-19 Jun
Fledglings: 29 Jun-12 Jul
Fall: summer <<<>>> Sep 29, 29, 30; summer <<<>>> Sep 13, 13, 14 (west); summer <<<>>> Sep 6, 7, 9 (brewsteri)
Later dates in the east are 3 Oct 2020 Buffalo Co, 8 Oct 2015 Douglas Co, 10 Oct 2015 Merrick Co, 13 Oct 1934 Webster Co (Ludlow 1935), and one extremely late that was banded at Neale Woods NC, Douglas Co 17 Nov 2001 (Betty Grenon and Craig Hensley, personal communication).
Later dates in the west are 16 Sep 2013 Scotts Bluff Co, 18 Sep 2013 Dawes Co, 19 Sep 2020 Scotts Bluff Co, 21 Sep 1997 Scotts Bluff Co, 21 Sep 2013 Banner Co, 22 Sep 2009 Dawes Co, and 25 Sep 2008 banded Scotts Bluff Co.
A later date for brewsteri is 15 Sep 2015 Fort Robinson, Dawes Co.
An earlier date for brewsteri away from the breeding range is 30 Jul 2019 Kiowa WMA, Scotts Bluff Co. Two very early Jul dates for brewsteri 3 Jul 2020 Box Butte Reservoir, Dawes Co and 4 Jul 2020 Pumpkin Creek, Banner Co are difficult to explain.
A banding record of interest is of a Warbling Vireo banded 20 May 1979 at Norfolk, Madison Co, Nebraska and recovered in Guatemala, where this species winters, 8 Oct 1982
Fall migration reports of “Western” Warbling Vireo tangibly documented are few and limited to the Panhandle. Five of seven birds netted at Oliver Reservoir, Kimball Co 31 Aug 2000 were clearly brewsteri, and two netted there 21 Aug 2001 were also brewsteri (Stephen J. Dinsmore, personal communication). One was photographed at Chadron SP’s banding station 3 Sep 2014 (LeFever 2014).
- High counts: 67 at Schuyler, Colfax Co 7 Sep 2014, 50 in Dakota Co 6 Sep 2014, and 17 at Ponca SP, Dixon Co 2 Sep 2018.
BBS: Breeding Bird Survey
NC: Nature Center
NNF: Nebraska National Forest
SHP: State Historical Park
UNSM: University of Nebraska State Museum
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.
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.
Gardali, T. and G. Ballard. 2020. Warbling Vireo (Vireo gilvus), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.warvir.01.
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.
Phillips, A.R. 1991. The known birds of North and Middle America. Part 2. Published by the author, Denver, Colorado, USA.
Pyle, P. 1997. Identification Guide to North American Birds. Part I, Columbidae to Ploceidae. Slate Creek Press, Bolinas, California, USA.
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.
Silcock, W.R., and J.G. Jorgensen. 2021. Warbling Vireo (Vireo gilvus). In Birds of Nebraska — Online. www.BirdsofNebraska.org
Birds of Nebraska – Online
Updated 4 Nov 2021