E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Oporornis agilis (Wilson, 1812)
Connecticut Warbler
Family: Parulidae

Species account author: Jamie Fenneman

Photo of species

© Robert Royse  Email the photographer   (Photo ID #11103)


Distribution of Oporornis agilis in British Columbia.
(Click on the map to view a larger version.)
Source: Distribution map provided by Jamie Fenneman for E-Fauna BC

Species Information

Adult male
The entire upperparts and nape are olive-green, slightly browner on the wings and tail. The uppertail and undertail coverts are noticeably long, extending about 2/3 of the way towards the tip of the tail. The entire underparts are relatively dull or pale yellow with an olive wash on the sides and flanks. The head (except for the nape) and upper breast are bluish-grey, sharply contrasting with the yellow underparts to form a hood; the grey is darkest on the centre of the breast, sometimes forming a diffuse blackish-grey patch. There is a distinct, narrow, complete white eye-ring. Birds in fresh fall plumage (acquired just prior to fall migration) have a more extensive brownish-olive wash over the nape, crown, and forehead and are tinged with brown on the upperparts. The iris is dark, the stout, pointed bill is pinkish with a dusky culmen and tip, and the legs and feet are bright pinkish.

Adult female
The plumage of the adult female is similar to that of the adult male, but the hood is strongly tinged with brown, contrasts less sharply with the yellow underparts, with a dull whitish to buffy throat that isolates the lower portion of the hood creating a brownish-grey band across the upper breast. The white eye-ring is often tinged with buff.

Immature
This plumage is acquired in the late summer of the first year, prior to fall migration, and is held until the following spring (February-April) but is lost before the species leaves the wintering grounds. Immatures of both sexes are similar to the adult female but are somewhat duller and browner, especially immature females. The throat is sometimes washed with pale yellow on particularly brownish individuals.

Juvenile
This plumage is held only briefly (4-6 weeks) after fledging and is lost before fall migration. The upperparts, breast, sides, and flanks are brownish and the underparts are pale yellowish. The throat is buffy and there is a narrow, complete buffy eye-ring. The legs are paler pink than in adult birds.

Measurements
Total Length: 14-15 cm
Mass: 15-15.5 cm

Source: Dunn and Garrett (1997); Pitocchelli et al. (1997)

Biology

Identification

The Connecticut Warbler is similar to both MacGillivray’s Warbler and Mourning Warbler in all plumages, especially immatures, but is usually easily distinguished from both species by its narrow, complete white or pale buff eye-ring. MacGillivray’s Warbler is brighter yellow below, has a darker grey hood with blackish lores and a blackish patch on the upper breast, and has a thicker eye-ring that is broken in front and behind the eye to form a pair of “eye-arcs.” In addition, the undertail and uppertail coverts of MacGillivray’s Warbler are noticeably shorter than in Connecticut Warbler, extending only ~1/3 of the length of the tail (extending ~2/3 of the length of the tail in Connecticut Warbler). Most Mourning Warblers, especially on the breeding grounds, can be distinguished from Connecticut Warbler by their lack of an eye-ring as well as their brighter yellow underparts, darker grey hood, and shorter uppertail and undertail coverts (extending ~1/2 of the length of the tail). Many Mourning Warblers, particularly immatures on fall migration, show a narrow whitish or pale buff eye ring that is reminiscent of Connecticut Warbler. The eye-ring is always broken in front of and/or behind the eye, unlike the uniform and complete eye-ring of the Connecticut Warbler.

Connecticut Warbler is also much more terrestrial than either MacGillivray’s or Mourning Warblers, and is often observed walking along the ground. Mourning and MacGillivray’s Warblers rarely venture to the ground, and when they do they move by hopping rather than walking. Vocalizations (both songs and calls) of Connecticut Warbler are very unlike either of the other two species and should be diagnostic if heard.

Source: Dunn and Garrett (1997)
Vocalizations

The song of the male is a loud, ringing, rollicking series of repeated 2- or 3-parted (sometimes 4-parted) phrases, starting slower and softer and building to a stronger, louder, and accelerated middle and end: beecher-beecher-beecher-beecher or chip-chuppy chip-chuppy chip-chuppy chip-chuppy. The song is reminiscent in tone and strength to the song of the Ovenbird or the latter portion of the song of the Northern Waterthrush, while the pattern is similar the song of the Common Yellowthroat. Call notes are heard relatively infrequently and include a sharp peek, a metallic plink, and a softer, nasal chimp or poit; the latter call is often heard in the vicinity of the nest. Also gives a buzzy zeet from flight or from a perch.

Source: Dunn and Garrett (1997); Pitocchelli et al. (1997); Sibley (2000)

Breeding Ecology

Courtship
Courtship and pair formation occurs immediately after arrival on the breeding grounds (late May-early June). Male song is the primary means of courtship. When singing, the male perches at heights of up to 8 m, often from branches within the open subcanopy of deciduous woodlands. The male often sings continuously for prolonged periods (up to several hours) during the height of the breeding season.

Nest
The nest is constructed in June, but little is known about the construction process. The nest is placed on the ground and is well-hidden in thick undergrowth, often at the base of a shrub or small sapling, in a clump of moss, or beneath overhanging dry grasses. The deep, compact nest is ~5 cm across and ~4 cm deep and is composed of fine dry grasses, dry leaves, and stems and is lined with rootlets, plant fibres, and animal hair.

Eggs
Clutches of (3) 4 (5) eggs are laid in late June or early July in B.C. The incubation period is unknown but is probably 12-13 days, and eggs are probably present in B.C. between late June and the third week of July. The smooth, slightly glossy eggs are creamy-white with reddish-brown and paler purplish or greyish-brown speckles and spots; these markings are usually concentrated at the larger end. This species is not known as a host for cowbird parasitism, but this is likely a reflection of the relative difficulty of locating nests and the small number nests that have been studied.

Young
The nestling period is unknown but is likely 8-10 days. Nestlings are altricial, with an orange mouth and yellow gape flanges. The young are tended by both parents, both before and after fledging.

Source: Baicich and Harrison (1997); Dunn and Garrett (1997); Pitocchelli et al. (1997); Campbell et al. (2001)
Foraging Ecology

This species is shy, inconspicuous, and secretive when foraging, and is often very difficult to locate. It commonly forages on the ground, bobbing its head back and forth or from side by side while walking and often peering upward. The tail is often bobbed slightly while walking. The terrestrial habits and walking (rather than hopping) means of locomotion are similar to the Ovenbird and very unlike other species in the genus Oporornis. It also forages in shrubs and trees, but maintains the walking gait when moving along branches. Insects and spiders form the bulk of the species’ diet on the breeding grounds and during migration, although seeds and berries are also consumed where they are available. Prey is taken directly from the ground or gleaned from twigs and leaves. It usually forages singly, although loose aggregations of up to a dozen individuals may rarely be encountered during migration.

Source: Dunn and Garrett (1997); Pitocchelli et al. (1997)

Habitat


The breeding habitat of this species in B.C. consists primarily of young (pole stage) to mature or old growth stands of Trembling Aspen on flat or gently sloping sites, particularly where the understory is relatively open and grassy and there are occasional young spruce trees within the subcanopy. Some individuals breed in drier aspen woods on hilltops and ridges. It occasionally occurs in younger deciduous woodlands of Balsam Poplar and willow, although there is usually at least some aspen component in the canopy. Migrants prefer low, dense, often moist tangles and thickets and have been found in bog habitats of spruce and Tamarack as well as in brushy riparian areas and along forest edges.

Source: Dunn and Garrett (1997); Campbell et al. (2001)

Distribution

Global Range

Breeds across much of the southern boreal forest of Canada, from northeast B.C. east to central Quebec, south to central Alberta and Saskatchewan, southern Manitoba, Minnesota, northern Wisconsin, northern Michigan, and central Ontario. Winters in northern South America. Migrants are infrequently seen, even along the primary migration routes, but occur widely across eastern North America in the spring and fall (more easterly in fall). Casual to very rare vagrant in western North America, primarily in California.
BC Distribution

Breeding
Generally uncommon in northeastern B.C. east of the Rocky Mountains, although locally fairly common in the Peace River region. Most records are from the Peace River and Fort Nelson lowlands.

Migration and Vagrancy
This species is rarely encountered during migration, with most individuals encountered only on the breeding grounds between early June and mid-July. Spring migrants arrive in northeastern B.C. from adjacent areas of Alberta during the last few days of May or in early June, and are among the latest breeding birds to arrive on the breeding grounds in this area. Although very few fall migrants have been detected in B.C., it appears that the fall movement out of the province occurs from late July to mid-August, with some perhaps lingering into late August or even early September.

The Connecticut Warbler is an accidental fall migrant in southeastern B.C. (Revelstoke; 12 September 2001) and on western Vancouver Island (Pacific Rim National Park; 27 October 1994).

Source: Campbell et al. (2001)

Conservation

Population and Conservation Status

Across its North American breeding range, populations appear to be stable or increasing, although some counts suggest declines and the species is not particularly common anywhere. There is some evidence that it was notably more common in the 1800s than during the present time, although reasons for this apparent decline are not known. It has traditionally been considered scarce in British Columbia, but targeted surveys in northeastern B.C. (particularly the Peace River area) in recent years have shown it to be fairly common in some areas. Despite this, however, it is still considered Endangered (red-listed) in B.C. by the Conservation Data Centre. It is not considered threatened by COSEWIC, suggesting that populations across Canada are overall secure.

Source: Dunn and Garrett (1997); Campbell et al. (2001)

Taxonomy


This species is monotypic, with no recognized subspecies. It appears to be distantly related to other members of the genus Oporornis and may deserve its own genus. It has possibly hybridized with Mourning Warbler, based on a specimen collected in spring in Oklahoma.

Source: Dunn and Garrett (1997)

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS3BBlueNot Listed
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-04-22 8:29:51 AM]
Disclaimer: The information contained in an E-Fauna BC atlas pages is derived from expert sources as cited (with permission) in each section. This information is scientifically based.  E-Fauna BC also acts as a portal to other sites via deep links.  As always, users should refer to the original sources for complete information.  E-Fauna BC is not responsible for the accuracy or completeness of the original information.


© E-Fauna BC 2021: An initiative of the Spatial Data Lab, Department of Geography, UBC