The First and Second Records of Bell’s Vireo (Vireo bellii) in British Columbia. By Rick Toochin. Published: June 3, 2023.

 

The Bell’s Vireo (Vireo bellii) is a small passerine that is found breeding in the lowland central and south-western United States and throughout Mexico. This species is migratory and winters from Mexico south through Central America into Guatemala south to northwestern Nicaragua.

 

There are four subspecies recognized, following Ridgway (Ridgway 1904) and all subsequent authorities (e.g., Phillips 1991).

 

The nominate (Vireo bellii bellii) breeds from scattered locations in Colorado (Bailey and Niedrach 1965, Chace 1998, Righter et al. 2004) in Yuma, Sedgwick, and Logan Counties, especially along the South Platte River (Andrews and Righter 1992, Kingery 1998); throughout Kansas (Thompson and Ely 1992), but not reported for far western counties except extreme northwest counties of Cheyenne and Rawlins (Busby and Zimmerman 2001); Nebraska, but casual in adjacent Wyoming; (Pettingill 1965, Sharpe et al. 2001); mainly along Missouri River and tributaries in both south and central South Dakota (Peterson 1995, Tallman et al. 2002) and throughout western North Dakota (Stewart 1975); southeastern Minnesota (Green and Janssen 1975), Iowa (Dinsmore et al. 1984), southern Wisconsin (Robbins 1991), Illinois (Bohlen 1989, Robinson 1996), central and southern Indiana (Nolan 1960), southern Michigan (Payne 1983, Granlund et al. 1994), western Ohio (Peterjohn 1989), Kentucky east to Ohio County; (Palmer-Ball 1996), rarely western Tennessee (Nicholson 1997), Missouri (Bennitt 1932), Arkansas (James and Neal 1986), northern Louisiana (Lowery 1974), and Oklahoma (Sutton 1967, Baumgartner and Baumgartner 1992, Byre 2004). Found throughout northeastern, northcentral Texas (Dunn and Alderfer 2017). This subspecies likely winters in coastal southwestern Mexico, south of Isthmus of Tehuantepec, south to northwestern Nicaragua (Kus et al. 2020). 

 

The second subspecies (V. b. medius) breeds from southwestern Texas south to northern Zacatecas and western San Luis Potosí in central Mexico (Kus et al. 2020). Its winter range unknown, but it is probably along the central Pacific coast of Mexico (Kus et al. 2020). 

 

The third subspecies (V. b. arizonae) breeds in eastern California  along the Colorado River and apparently west into the eastern Mojave Desert (Kus et al. 2020), southern Nevada (Linsdale 1936, Alcorn 1988), uncommonly in Washington County, southwestern Utah especially Virgin River drainage and Beaver Dam Wash (Hardy and Higgins 1940, Behle and Perry 1975, Hayward et al. 1976, Behle et al. 1985, Wauer 1997, Parrish et al. 1999), also in northwestern, central, and southern Arizona (Phillips et al. 1964, Phillips 1968, Monson and Phillips 1964), and southern New Mexico (Bailey 1928, Hubbard 1978); south and east to southern Sonora, western Texas, and Chihuahua (Kus et al. 2020). This subspecies likely winter in northwestern Mexico, but there is a single winter record for southern California (Kus et al. 2020). 

 

The fourth subspecies is also called the Least Bell's Vireo(V. b. pusillus) which also includes (V. b. albatus) is an endangered subspecies that breeds from central California south to northern Baja California (Kus et al. 2020). This subspecies has a breeding range that has severely contracted from its historic distribution in Tehama County, south through the Central Valley, coastal Santa Clara County to San Diego County, and Owens Valley, Death Valley, and scattered oases in Mojave Desert in California (Kus et al. 2020) Best estimates available for the endangered Least Bell's Vireo population in California are a statewide population in 2008 that numbered approximately 3,000 territorial males (U. S. Fish and Wildlife Service 2006).  This subspecies winters in southern Baja California Sur, with some winter records north to southwestern California (Kus et al. 2020).

 

In northern Mexico the Bell’s Vireo range is not well known (Miller 1957, Phillips 1991, Howell and Webb 2010). It is found in northwestern Baja California Norte and was formerly in the northeast region along the Rio Colorado, but now probably extirpated owing to loss of riparian habitat (Wilbur 1987, Patten et al. 2001, Erickson and Howell 2001). There are recent records from the Baja California Sur that are particularly important because this species is declining throughout its range to the north (Hamilton and Erickson 2001). The Bell’s Vireo is also found in most of the lowland Sonora away from Pacific coast (Russell and Monson 1998); also in the southeastern Sinaloa, central Zacatecas, north San Luis Potosi, southwestern Tamaulipas (Phillips 1991); and throughout parts of lowland Chihuahua (Hubbard and Crossin 1975) and Coahuila (Urban 1959), Durango (Fleming and Baker 1963, Hubbard and Crossin 1975), and Nuevo Leon, south along the west coast of Mexico through Colima (Schaldach 1963) and Oaxaca (Rowley 1966) to Central America including El Salvador (Thurber et al. 1987). It is known to occur casually to southern Honduras and Nicaragua (Monroe 1968, Phillips 1991); primarily on the Pacific slope and in the interior of Middle America, to Honduras, casually to north-central Nicaragua (American Ornithologists' Union 1998).

 

In North America, the Bell’s Vireo is a possible rare wintering bird up and down on the Atlantic coast (Howell and Webb 2010). There are scattered winter records from north to central California (McCaskie and Banks 1964, McCaskie 1970, Kus et al. 2020), southern and central Arizona (Rea 1983), southern Texas, Louisiana, and southern Florida (American Ornithologists' Union 1998). In Texas, the Bell’s Vireo is classified as a very rare winter visitor in lower Rio Grande Valley with one documented winter record from El Paso County (Texas Ornithological Society 2004).

There have been many historical changes in this species overall distribution over the past 100 years. During the 1900s, there was a slight northern and eastern expansion of the Bell’s Vireo recorded breeding range. From 1953 to 1982, this range expanded at least 232 km up the Colorado River into the Grand Canyon in Arizona (Brown et al. 1983). Breeding populations of the subspecies (V. b. arizonae) nearly extirpated in the Lower Colorado River Valley in California and Arizona (Rosenberg et al. 1991); (V. b. pusillus) extirpated from most of its historic range in California by early 1980's with the remaining small populations concentrated in coastal southern California (Goldwasser et al. 1980, Franzreb 1989, U. S. Fish and Wildlife Service 1998) and nearly extirpated in Baja California Sur (Wilbur 1987). Since the late 1980's and the implementation of wide scale habitat protection and Brown-headed Cowbird (Molothrus ater) control, (V. b. pusillus) has increased in abundance and distribution throughout southern and central California, including a recent colonization of the San Joaquin River in Stanislaus Co. (Howell and Dettling 2009).

Reports of recent northward expansion of breeding range is difficult to determine because this could be a result of better observer coverage, and widespread habitat alterations, especially along water courses, or other causes (Kus et al. 2020). In some regions, there is a definite decrease in numbers and local distribution while in others there has been an apparent increase (Kus et al. 2020). The major causes of changes in distribution of this species are generally attributed to either habitat changes through activities of Euro-American settlers or Brown-headed Cowbird brood parasitism (Brown 1994). Habitat changes in the past include water projects and resulting changes in riparian scrub, development of hedgerows, windbreaks, and parks associated with rural and urban development, changes in farming practices, particularly in the Great Plains, and increasing deforestation and other activities that result in clearing of favored vegetation and successional development of riparian and upland scrub (Shugart and James 1973).

Although Brown-headed Cowbird brood parasitism is commonly given as a major cause for the decline in distribution and populations, habitat alteration is considered by many to be the leading cause (Pulich 1979, Russell and Monson 1998, Alsop III 2002, Kus et al. 2020). In Nebraska, suggested decline in some sections due to water projects, which included brush clearing, while increase in other sections due to decreased stream flow downstream from dams and resulting increased riparian scrub (Sharpe et al. 2001). In South Dakota, decreasing vegetation downstream from dams, resulting from a lack of stream flow, has coincided with decreasing Bell's Vireo populations (Tallman et al. 2002). Also decreases in Iowa (Jackson et al. 1996), and in southern Wisconsin (with few Bells’ Vireo) where a colony disappeared after destruction of black locust (Robinia psuedoacacia) trees during a prairie restoration project (Robbins 1991). Increases in Iowa are possibly due to deforestation and resultant successional scrub (Jackson et al. 1996). Possible increases owing to surface (strip) mining in Franklin and Williamson Counties in southern Illinois (Karr 1968, Robinson 1996) and Muhlenberg and Ohio Counties in Kentucky (Palmer-Ball 1996). In Arizona, a decrease in population is attributed largely to Brown-headed Cowbird parasitism by some (Phillips et al. 1964, Monson and Phillips 1964), but others attribute most of the decline to habitat destruction (Rea 1983, Rosenberg et al. 1991, Johnson et al. 2000). At Blue Point Cottonwoods, Salt River, Maricopa County in Arizona, both Bronzed Cowbird (Molothrus aeneus) and Brown-headed Cowbird bred from 1969-1990s, but Bell's Vireo continued as the 17th most common breeding species among 69 species listed (Johnson et al. 2000).

Use of playback tapes increases probability of finding the species in areas where changes may be suspected (Johnson et al. 1981). Some authors who have written about the impacts of loss of riparian habitat on birds also attribute population reduction in Bell's Vireo to cowbirds without mentioning the interrelationship between riparian clearing projects, increases in vegetation patchiness and consequential cowbird populations, and the cumulative impact on this small vireo and other riparian nesting birds (e.g., Grinnell and Miller 1944, Phillips and Monson 1964, Phillips 1968). Kus et al. (2020) conclude that brood parasitism is usually a secondary effect, compounding losses in populations that have been largely to entirely extirpated by loss of riparian habitat.

Bell's Vireo rapidly colonizes newly established habitats, especially successional stages resulting from human activity, e.g., timber harvest, old-field succession (Shugart and James 1973), and riparian scrub resulting from dam construction and associated water projects. The species was considered hypothetical for Kentucky by Mengel (1965) in the 1960s, but later several pairs were reported nesting there at the TVA Shawnee Steam Plant and on adjacent West Kentucky Wildlife Management Area (Palmer-Ball 1996).

The best documented expansion for Bell's Vireo is an upstream advance of approximately 320 km (200 mi) along the Colorado River in Grand Canyon between 1953 and 1997. This increasing population nested in riparian scrub resulting from changes in stream flow after the construction of upstream Glen Canyon Dam (Carothers and Johnson 1975, Carothers and Brown 1991). This is also in an area where Brown-headed Cowbirds are present (Brown et al. 1987). The species was so poorly known that it was not mentioned in an account of biological work throughout Grand Canyon from May 8 to September 9, 1931, by Florence Merriam Bailey and Vernon Bailey, 2 of the most prominent ornithologists of the period (Bailey 1939). In the next detailed report of uncommon and rare species for Grand Canyon the species, again, was not mentioned (Carothers and Johnson 1975) although it was recorded in 1953 at RM 188 (River Miles below Lees Ferry) (Monson 1953). By 1982 it had advanced upriver to RM 43 (Brown et al. 1983, Carothers and Brown 1991, Brown et al. 1987), and by 1997 had colonized upstream to Glen Canyon Dam and possibly Lake Powell, above the dam (LaRue et al. 2001).

Like other vireos, Bell's Vireos are heavily parasitized by the Brown-headed Cowbird and parasitism has exacerbated declines resulting from habitat loss and degradation throughout the species' range (Kus 1999). Since the Least Bell's Vireo was listed as Endangered in California in 1986, an upsurge of research has expanded our knowledge of the breeding ecology and demography of Bell's Vireos, particularly regarding parasite-host interactions (Kus et al. 2020). Considered a flagship species representative of many low shrub-nesting species, this vireo is increasingly the subject of research and conservation promoting protection of avian biodiversity (Kus et al. 2020). Breeding Bird Survey records indicate area with the highest mean number of Bell's Vireos per survey route in 2007 was Edwards Plateau (Texas, 10.5), while the highest overall state mean was Arizona (2.16), (Sauer et al. 2008, Kus et al. 2020). 

It is difficult to determine if increasing reports of vagrant Bell's Vireo are due to actual range extensions and increasing movements, better observer coverage, or both (Patten 1999). Vagrants have been recorded in Ontario, Nova Scotia and from New England south to Florida along the east coast of North America. An excellent summary of extralimital records for the eastern U.S. and Canada is by Patten (1999).

North of the western range of the Bell’s Vireo, this species is a casual to accidental migrant vagrant with a small, but slowly growing number of records. In Oregon there is a single accepted record by the Oregon Bird Records Committee of a bird found singing in Fields, Harney County on June 6, 1998 (OFO 2020). Idaho also has a single accepted record by the Idaho Bird Records Committee of an adult bird found at Camas National Wildlife Refuge in Jefferson County on May 28-29, 1998 (Trochlell and Svingen 1998).  Amazingly Washington State has 4 accepted records of single Bell’s Vireo by the Washington Bird Committee. These include A bird found at the Skagit Wildlife Area in Skagit County, from September 27-28, 2007 (Merrill and Bartels 2015); another bird found at Washtucna in Adams County, on September 6, 2008 (Merrill and Bartels 2015); another singing bird found at Sun Lakes State Park in Grant County on May 20, 2009 (Merrill and Bartels 2015); and a bird photographed at St. Andrews in Douglas County on June 6, 2010 (Mlodinow and Bartels 2016). Of note the fourth record photographs suggest this bird was of the subspecies (V. b. bellii). The Bell’s Vireo is a new addition to the avifauna list of British Columbia (Toochin et al. 2018).

 

The identification of the Bell’s Vireo is covered in all standard field guides for North America. This is a small vireo measuring 12 in length, with a wingspan of 18 cm, and weighs 8.5 grams (Sibley 2000, Dunn and Alderfer 2017). Overall, the Bell’s Vireo has short, rounded wings that make the tail look long (Sibley 2000). This species has a short, straight, blunt-tipped bill, somewhat compressed at the base (Sibley 2000, Dunn and Alderfer 2017). Bell’s Vireo is sexually monomorphic in plumage coloration throughout the year (Kus et al. 2020). 

Adult plumage color varies regionally with different subspecies, but generally birds are drab gray to green above, white to yellow below; the breast is unstreaked (Kus et al. 2020). There is a faint white eye-ring; the eyes are dark brown to black (Sibley 2000). The upper mandible black (especially on culmen) to grayish-black or pale brown; lower mandible grayish black to pale brown; gape yellowish (Kus et al. 2020). There are two pale wing bars, with the lower bar appearing more prominent (Kus et al. 2020). The legs and feet are dark grayish blue to black (Dunn and Alderfer 2017).

 Juvenile plumage resembles that of adults in worn summer plumage and is essentially white and gray, but whiter below with more distinct wingbars (Kus et al. 2020). Least Bell's Vireo juveniles have pale whitish cheeks and forehead, green in wings and tail (Kus et al. 2020).

Identification of the four subspecies can be identified in the field, but there is slight overlap making some vagrant birds difficult to identify to subspecies (Patten 1999). The following descriptions follow Ridgway (Ridgway 1904) and all subsequent authorities (e.g., Phillips 1991). Each subspecies has slightly different plumage characteristics.

The nominate subspecies (V. b. bellii) has a grayish brown crown and nape; the mantle is greenish-olive; the sides and flanks are greenish yellow; and the undertail coverts and axillars are sulphur-yellow.

The subspecies (V. b. medius) appear like the nominate (V. b. bellii), but crown is browner and the nape grayer, with a more gray-olive mantle, and yellow flanks are paler. The undertail coverts and axillars white or yellowish white; and the tail averages longer.

The subspecies (V. b. arizonae) are like the subspecies (V. b. medius), but crown, nape, and mantle are brownish gray, the flanks are pale grayish-yellow, and the undertail coverts are white. The tail and legs average longer.

The subspecies (V. b. pusillus) are like the subspecies (V. b. arizonae), but dorsum largely gray, with the only rump and uppertail coverts are washed olive, and the ventrum is nearly white, with only faint yellow on the flanks. The wings and tail average longer.

The Bell’s Vireo is a small, active vireo that often flicks or bobs the tail while foraging in dense thickets (Kus et al. 2020). The nominate Bell's Vireo (V. b. bellii) breeding east of west Texas is brighter and more colorful overall than the western breeding birds, but some intermediate birds occur (Sibley 2000, Dunn and Alderfer 2017). Populations in Arizona (V. b. arizonae) and the California "Least Bell's Vireo" (V. b. pusillus) are drabber, and Least Bell's Vireos are virtually entirely grayish (Kus et al. 2020). Eastern birds bob tail, whereas the western birds flip the tail up and to the side like a Gnatcatcher (Sibley 2000).

In the context of British Columbia, the Bell’s Vireo is distinguished from the similar Warbling Vireo (Vireo gilvus) by smaller and slimmer build, white wingbars, and a more 'spectacled' appearance (Sibley 2000, Dunn and Alderfer 2017). The active foraging behavior of Bell's Vireo often recalls Ruby-crowned Kinglet (Regulus calendula) but note the vireo's thicker bluish legs and stout bill (Kus et al. 2020). 

The song of the Bell’s Vireo is a husky, chatty, musical “chewede jechewide cheedle jeew” with slight emphasis on the ending, but basically sounds flat (Sibley 2000). Variations do occur in detail, but the quality of the song is quite distinctive (Sibley 2000, Dunn and Alderfer 2017). 

 

The call notes are a fairly high, soft nasal “biiv biiv” or “chee chee” (Sibley 2000). Another similar call that is given singly is a nasal rising “mree” that is often repeated (Sibley 2000).

 

The Bell’s Vireo is an accidental migrant vagrant to British Columbia and was recently added to the avifauna list of the province (Toochin et al. 2018). This first record was of a worn adult found by Anne (Aziza) Cooper and was seen and photographed by multiple observers at Island View Beach in Saanich from September 6-21, 2020 (D. Cecile Pers. Comm.). Detailed recordings and photographs were taken of this bird, and it was thought to best match the eastern subspecies (V. b. bellii) (D. Cecile Pers. Comm.). This makes sense given that the eastern subspecies of Bell’s Vireo is more widespread and is likely the most migratory of the subspecies to wander into the Pacific Northwest. The 4 records for Washington, the single record for British Columbia, and the single record for Idaho fit the timing of vagrancy that is exhibited by eastern birds with overshoots occurring in the spring from late May into early-mid June and birds wandering in the fall from September into November. The second record for British Columbia was of an adult of the eastern subspecies  found and photographed by Steven Roias and Amelie Rousseau, and many other observers at Panama Flats in Victoria from November 6-9, 2022 (D. Cecile Pers. Comm.). Since Bell’s Vireos populations in the mid-western states are migratory, it is highly likely that more records will occur in British Columbia in the future. This species can turn up anywhere in the province in appropriate habitat and should be watched for by keen observers in all known vagrant traps. 

I wish to thank Don Cecile for providing information on the first British Columbia record and for editing the original manuscript. I would like to thank Liam Singh for the use of his pictures of the Bell’s Vireo found in Saanich for this article. All photos are used with permission of the photographer and are fully protected by copyright law. Photographs are not to be reproduced, published or retransmitted on any website without the authorization of the photographer.

 

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