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 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 2000).
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); 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.
Spring: Apr 14, 16, 18 <<<>>> summer; Apr 26, 26, 27 <<<>>> summer (west),
There is an early date at Fontenelle Forest, Sarpy Co 9 Apr 2008.
Migration data indicate that arrival in the Panhandle is about 10 days later than elsewhere, perhaps in part due to differing schedules of the two subspecies discussed above.
Reports of western brewsteri during migration are few; the five reports are 18 May-4 Jun.
- 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
Eggs: 3-19 Jun
Fledglings: 12 Jul
Fall: summer <<<>>> Oct 5, 5, 5; summer <<<>>> Sep 14, 15, 16 (west)
Departure in the Panhandle is completed by early Sep, elsewhere by early Oct, an approximate 20-day difference, as in spring; this suggests differing migration schedules of the two subspecies.
There are later reports from the Panhandle 21 Sep 2013 Banner Co, 25 Sep 2008 banded Scotts Bluff Co, 30 Sep 1994 Scotts Bluff Co, 2 Oct 2004 Scotts Bluff Co, and 8 Oct 1978 Garden Co. Elsewhere there are later reports 8 Oct 2015 Omaha, Douglas Co, 10 Oct 2015 Merrick Co, 13 Oct 1934 Webster Co (Ludlow 1935), 20 Oct 1977 Howard-Hall Cos, and one extremely late that was banded at Neale Woods NC, Douglas Co 17 Nov 2001 (Betty Grenon and Craig Hensley, personal communication). These later reports also reflect differential migration timing between the west and elsewhere.
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.
Documented fall migration reports of “Western” Warbling Vireo 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). Other reports are of one in Scotts Bluff Co 30 Jul 2019, two in Kimball Co 2 Sep 2018, one “brighter than eastern birds” 6 Sep 2015 Dawes Co, one in Kimball Co 7 Sep 2015, and one at Fort Robinson SHP, Dawes Co 15 Sep 2015.
- 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
Photograph (top) of a Warbling Vireo at Papillion, Sarpy Co 6 May 2014 by Phil Swanson.
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. 2000. Warbling Vireo (Vireo gilvus), version 2.0. In The Birds of North America, #551. https://doi.org/10.2173/bna.551.
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. 2018. Warbling Vireo (Vireo gilvus), Version 1.0. In Birds of Nebraska — Online. www.BirdsofNebraska.org