The First Sight Record of Kentucky Warbler (Geothlypis formosa) in British Columbia. By Rick Toochin. Published: June 3, 2023.

The Kentucky Warbler (Geothlypis formosa) is a small passerine that is found breeding in deep deciduous woodlands and less commonly in mixed deciduous-conifer woodlands with extensive shade and considerable shrubby growth and ground cover in southeastern North America (Dunn and Garrett 1997). This species regularly breeds north to north-central New Jersey (USGS 2018), central Pennsylvania (Brauning 1992), northern Ohio (Peterjohn 1989), central Indiana (USGS 2018), north-central Illinois (Kleen et al. 2004, USGS 2018), southeastern Iowa from Lee and Van Buren Counties, westward along Des Moines River valley (Cecil 1996b, IBBA 2020), and in north-central Missouri, where it is rare in the northernmost part of state (Robbins and Easterla 1992). The Kentucky Warbler also breeds from northernmost Illinois (Kleen et al. 2004), north to extreme northeastern Iowa (Cecil 1996b), and southwestern Wisconsin (WIBBA 2003), and in extreme southeastern New York (McGowan and Corwin 2008) and rare in southern Connecticut (Clark 1994h).

The breeding range of the Kentucky Warbler extends south along the Atlantic Coast south to South Carolina, except on the southwest coastal plain (McNair and Post 1993b), south into Georgia to Screven County (Haney et al. 1986), the panhandle of Florida east to Suwannee County (Robertson and Woolfenden 1992) and the Gulf Coast but absent from coastal portions of southern Louisiana and southern Texas (Tweit 2005b; TXBBA 2012).

The western limits of the Kentucky Warbler’s breeding range extend, particularly along wooded river valleys, to extreme southwestern Iowa (Cecil 1996b) and extreme southeastern Nebraska (Johnsgard 1979), eastern Kansas (Busby and Zimmerman 2001), eastern Oklahoma (Reinking 2004), and the eastern quarter of Texas with nearly all records occurring east of 96°W (TXBBA 2012).

This species is observed annually during the breeding season in areas north of its regular breeding range. Most of these records are of single males, but pairs occasionally recorded in areas north to Massachusetts (Veit and Petersen 1993), extreme southern Ontario (McCracken 1987b), southern Michigan (Reinoehl 1991a), and southeastern Minnesota (Janssen 1987). Breeding is suspected in these observations, but rarely documented within this overshoot area (Reinoehl 1991a). The Kentucky Warbler also occurs locally during the breeding season west to central Kansas and central Oklahoma (Johnsgard 1979, Baumgartner and Baumgartner 1992), and has been recorded accidentally in other areas outside of the regular breeding range, including in California (Dunn and Garrett 1997). There are also spring records for Arizona, New Mexico, and Colorado (Dunn and Garrett 1997). The Kentucky Warbler has also been reported in Sonora, Mexico (Howell and Webb 2010).

The Kentucky Warbler often occurs as a “spring overshoot” or vagrant beyond the areas of New England and the Canadian Maritimes and include occurrences in such Canadian Provinces and in the in mid-western United States (Dunn and Garrett 1997).

The Kentucky Warbler completes a full migration between the breeding grounds in North America and the wintering grounds in Neotropics (Curson et al. 1994). This species appears to migrate nocturnally (Rappole and Warner 1976). In Florida, the number of birds killed at towers during spring migration is considerably higher along the Florida Panhandle than at points in eastern Florida, suggesting that more migrants arrive along north Gulf of Mexico than along Florida coast (Stevenson and Anderson 1994). The main northbound migration route, however, is north and northeast through mainland Mexico and eastern Texas to the Mississippi River valley, whence birds fan out to settle the bottomland forest of large rivers, primarily west of the Alleghenies and east of the Great Plains (Bent 1953). Northbound migrants have been reported as fairly common in April in northeastern Mexico, and as vagrant in Sonora, Mexico, in mid-June (Howell and Webb 2010).

Although most individuals appear to travel between breeding and wintering grounds via the Gulf of Mexico and eastern Mexico, small numbers also use a more easterly route (McDonald 2020). Transients have been recorded in Bermuda, throughout the Caribbean, east to the Virgin Islands, but very rarely in the Lesser Antilles (Evans 1990) and south to the Netherlands Antilles (McDonald 2020). Most records of transients in Bermuda (Amos 1991) and all records of transients from Bonaire and Aruba (Voous 1983) are from autumn.

On wintering grounds, has been recorded through late April in Panama (Ridgely and Gwynne 1989) and Costa Rica (Stiles and Skutch 1989), and April in Mexico (Howell and Webb 2010). Migrants have arrived as early as late March in Florida (Robertson and Woolfenden 1992, Stevenson and Anderson 1994). Most migrants observed mid-Apr–early May in Texas with extreme early date of March 18, and extreme late date of June 5 (Oberholser 1974). In Arkansas, this species may arrive in the south in late March or early April, but most migrants arrive in mid-April through second week of May (James and Neal 1986). In Kentucky, the first birds are observed by late April, with bulk of birds arriving by early May (Palmer-Ball 1996). This is also true for Maryland (Robbins and Blom 1996), and Cape May, New Jersey (Sibley 1997). The first birds arrive in late April in southern Ohio and early May in northern Ohio, with most birds returning by mid-May (Peterjohn 1989). Breeding birds have mostly returned to southwestern Wisconsin from May 5-15 (Robbins 1991).

Outside the main migration path, the Kentucky Warbler has been recorded from March 15 and April 8 in Bermuda (Amos 1991). Individuals are observed annually during spring migration in areas well north of the species regular breeding range (Janssen 1987, Veit and Petersen 1993).

In fall, territorial birds disappear from their breeding grounds in Virginia from early August–mid-September; presumably starting migration. However, disappearance of migratory birds from breeding grounds is not necessarily commensurate with initiation of fall migration (Rappole and Ballard 1987). Kentucky Warblers often appear in Massachusetts during the fall, north of their regular breeding range; most fall records are from August 20–September 10 (Veit and Petersen 1993). In Minnesota, a possible fall migrant was captured aboard a ship in the western part of Lake Superior July 24, 1964 (Janssen 1987). Most birds apparently leave Ohio between last half of August and from September 10-20 with the latest observation recorded on October 17 (Peterjohn 1989). Migrants have arrived in Cape May, New Jersey, as early as August 5 and are generally observed through early September with the latest observed in mid-September (Sibley 1997). Most depart Maryland by early August through early mid-September (Robbins and Blom 1996). Migrants are observed in Arkansas through till late September with the latest date record on October 6 (James and Neal 1986). In western Florida, 9 tower kills recorded from July 21–31, but much larger numbers have struck towers in this area between August 11 and October 10 (Stevenson and Anderson 1994). In Middle America, the earliest fall records are from August in Mexico (Howell and Webb 2010), early–mid-September for Costa Rica (Stiles and Skutch 1989), and early September for Panama (Ridgely and Gwynne 1989).

Outside the main migration path, the Kentucky Warbler is recorded regularly in Bermuda from mid-August to mid-September with extremely early birds having been found August 14 and late birds found on October 19 (Amos 1991). On Aruba and Bonaire, recorded only in fall with 1 record for September and 6 records for October (Voous 1983).

The Kentucky Warbler winters primarily from Mexico south through Central America to northern portions of Colombia and Venezuela (Dunn and Garrett 1997). Also recorded in winter in Bermuda and throughout much of Caribbean, where small numbers may winter regularly on some islands (Amos 1991).

In Mexico, winters from extreme southwestern Tamaulipas and southeastern San Luis Potosí south to central Veracruz and northern Oaxaca (Howell and Webb 2010). From Oaxaca and Veracruz, winters south along Pacific slope to southeastern Guatemala, very rarely to El Salvador, and south along Atlantic slope throughout Yucatán Peninsula, except absent from state of Yucatán, Belize, and northern Guatemala to northern Honduras (Howell and Webb 2010). This species is very rare in winter along the Pacific slope of Mexico north to Nayarit (Howell and Webb 2010). One recent record, in April 2009, from west of the Isthmus in the Pacific region of Oaxaca, 1.2 km E Unión Hidalgo, could have been a winter resident or migrant (McAndrews and Montejo Díaz 2010). The Kentucky Warbler was previously hypothetical, but now is confirmed in Nuevo Leon (Valdes-Pena et al. 2009).

There is no information on the winter distribution of the Kentucky Warbler in Nicaragua, but this species probably winters along the Atlantic slope as it does in Honduras and Costa Rica. In Costa Rica, winters in lowlands of both Atlantic and Pacific slopes (regularly to 1,200 m and locally to 1,850 m) but most numerous on southern Pacific slope, and least numerous along northern Pacific slope  (Stiles and Skutch 1989). In Panama, winters in lowlands throughout, but most numerous in western and central provinces. Small numbers recorded in highlands during migration (Ridgely and Gwynne 1989).

Winter range of the Kentucky Warbler extends south to northeastern Colombia with records from Magdalena, El Cesar, and Santander, and northwestern Venezuela with records from Mérida, Zulia, and possibly Táchira and Aragua, but the distribution in South America is based on relatively few records and remains poorly known (Paynter 1995).

The species has been recorded in Bermuda (Amos 1991), Cayman Islands (Pashley 1988c), Cuba (Garrido and Kirkconnell 1993), Jamaica (Wunderle and Wade 1993), Dominican Republic (Dod 1981), Puerto Rico (Raffaele 1989), and United States Virgin Islands (Raffaele 1989) during the winter. Records are too few for most islands to suggest regular wintering on most islands, but repeated winter records from Puerto Rico (Pashley and Martin 1988, Wunderle and Wade 1993), and St. John, Virgin Islands (Raffaele 1989), suggest that small numbers may winter regularly on those islands.

The Kentucky Warbler is a casual visitor to the Lesser Antilles as far south as Guadeloupe Island (AOU 1998, Feldmann et al. 1999). There are also reports of the Kentucky Warbler from Barbados, and even further south in the Lesser Antilles (McDonald 2020).

Has also been recorded in Florida during the winter, including 1 specimen from Dade County collected on January 23, 1960 (Stevenson and Anderson 1994), Texas (Oberholser 1974), California (Small 1994) and other areas of the southern United States during the winter, but winter records in United States appear to be highly unusual (Dunn and Garrett 1997).

The species is also a very rare transient in western United States, where it has been recorded in several states including North and South Dakota (e-bird database 2021), Utah (e-bird database 2021), Montana (e-bird database 2021), Arizona (Rosenberg et al. 1991), New Mexico, and Nevada (Alcorn 1988). 

 

The Kentucky Warbler is accidental in the western Canada with 2 records from Manitoba, with the first a bird found in the Winnipeg area on September 18, 1994 and the second an adult male found at Atona from May 21-22, 1996 (e-bird database 2021); 1 photographed record from Saskatchewan of an adult male at Chief Whitecap Park, in Saskatoon from October 5-9, 2021 (e-bird database 2021); 1 record from Alberta of an adult male at Weaselhead Nature Area in Calgary from June 18-21, 1988 (e-bird database 2021).

Along the west coast of North America, the Kentucky Warbler is most frequently in California where there 110 accepted records by the California Bird Records Committee (Hamilton et al. 2007, Tietz and McCaskie 2020). In California, it is a very rare spring migrant (1–2 records per season) and extremely rare fall migrant (Hamilton et al. 2007, Tietz and McCaskie 2020). In spring, occurs from mid May – mid June with most southern records coming from the eastern deserts, while most northern records come from the coast, particularly Farallon Islands (Small 1994, Hamilton et al. 2007, Tietz and McCaskie 2020). In 1987, an unprecedented number of 14 individuals were recorded during that spring in California (Small 1994). In California, where fall migrants are extremely rare, most are recorded from the months of September and October; with extremely early dates occurring in mid-August and extremely late dates occurring in late November (Small 1994, Hamilton et al. 2007, Tietz and McCaskie 2020). In Oregon, the Kentucky Warbler is an accidental migrant vagrant with only 4 accepted records by the Oregon Bird Records Committee (Gilligan et al. 1994, OFO 2020). These records are as follows:  1 bird found in Fields, Harney County on 16 June 1989; 1 male in alternate plumage photographed at Frenchglen, Harney County, on 8 June 1990; 1 singing male photographed/videotaped at Dead Cow Creek Fremont NF, Lake County from June 23-July 20, 1996; ., 1 singing male at Fields, Harney County on May 8, 2000; and 1 bird found West of Grants Pass, south side of Hwy. 199, in Josephine County on September 25, 2017 (Gilligan et al. 1994, OFO 2020). The Kentucky Warbler is an accidental migrant in British Columbia with a well described fall record from Vancouver Island (Toochin et al. 2018). This species has also been recorded as a well documented sight record from Alaska at Beaufort Lagoon on September 19, 1982 (Dunn and Garrett 1997).

The identification of the Kentucky Warbler is covered in all standard North American field guides. This is a medium-sized warbler measuring 13 cm in length, with a wingspan of 22 cm, weighs 14 g (Sibley 2000, Dunn and Alderfer 2011). This species is obvious looking species at any age and should not pose any difficulty in identification. The Adult male has olive green upperparts, bright yellow underparts (Dunn and Garrett 1997). Forehead, crown, and side of head black, forming a black “mask” (McDonald 2021). The black mask is interrupted by a yellow supraloral stripe, which joins an incomplete yellow eye-ring, forming yellow “spectacles” (Sibley 2000). There are no wing-bars or tail-spots (Sibley 2000). The tail is short and the legs pale pinkish (Dunn and Alderfer 2011). The adult female is like the male, but the black on the head is usually, but not always, reduced or mottled with grayish olive (Dunn and Alderfer 2011). Immature birds are like, but duller than adults of the same sex (Dunn and Garrett 1997). Plumages are similar throughout year (McDonald 2021).

The Kentucky Warbler is unique in appearance and not easily confused with other warbler species. It is most like Common Yellowthroat (Geothlypis trichas) (McDonald 2020). In all plumages, however, Kentucky Warbler is distinguished by presence of yellow spectacles, which are never present on a Common Yellowthroat (Sibley 2000).

The Kentucky Warbler could also potentially be confused with a Hooded Warbler (Wilsonia citrina) or Canada Warbler (Wilsonia canadensis) (McDonald 2020). However, Hooded Warbler has a variable black hood, entirely yellow face (not just yellow spectacles), and white tail-spots (lacking in Kentucky) (Curson et al. 1994). Canada Warbler is gray on upperparts (not olive green), with streaked (not plain) upper breast, and white (not yellow) undertail-coverts (Dunn and Garrett 1997).

Male Kentucky Warblers sing a relatively simple song of rich and rolling series of 5-8 repeated up-slurred phrases of “churee churee churee” or “tory-tory-tory-tory”, not unlike that of Carolina Wren (Thryothorus ludovicianus) (Dunn and Garrett 1997). However, Kentucky Warbler's song can be distinguished from that of a Carolina Wren by the fact that the warbler typically sings the same song pattern repeatedly, while individual Carolina Wrens sing several different song patterns, often changing patterns within a single song bout (McDonald 2020). The most common call is a low distinct “chup” or “chuck” call note which is usually given when birds are alarmed (Dunn and Garrett 1997). 

The Kentucky Warbler is an accidental migrant vagrant in British Columbia with a single sight record (Toochin et al. 2018). The only record was an immature male found by experienced observer David Aldcroft at Pipers Lagoon, in Nanaimo on September 19, 2004 (Toochin et al. 2018). This record is a well-documented through field notes and verbal documentation to the author (R. Toochin Pers Comm.). Bird occurring in the fall are much rare in western North America, but this bird’s occurrence fits into the fall pattern of vagrancy that has been establish in California and other western states. In British Columbia, the established pattern of vagrancy in the spring, also called “spring overshoots” is from late May into mid-June (Toochin et al. 2018). This holds true for other southeastern warblers that have turned up as vagrants in the province in this time frame such as Golden-winged Warbler (Vermivora chrysoptera), Prothonotary Warbler (Protonotaria citrea),Hooded Warbler, and Northern Parula (Setophaga americana) (Toochin et al. 2018). It would seem very likely to hold true for any future records of Kentucky Warbler in the province. This species can turn up anywhere in the British Columbia, but it should be watched for at both banding stations and known vagrant traps in spring and in the fall. It is very likely that the Kentucky Warbler will show up again in province in the future.

I want to thank Don Cecile for editing the original manuscript. I also wish to thank Dave Aldcroft for providing information on his sighting.

 

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