Canada Warbler Cardellina canadensis
Version: 2.0 — Published May 7, 2020
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Habitat in Breeding Range
Wide range of deciduous and coniferous forests. Most abundant in moist, mixed coniferous–deciduous forests with a well-developed understory. Often near open water. Common at higher elevations (hills and mountains), especially in southern portion of range (91, 92). At lower elevations, often restricted to cool, wet, low-lying areas: cedar (Cupressaceae) woods, red maple (Acer rubrum) swamps, sphagnum (Sphagnum) bogs, moist forest clearings and woodland edges, spruce–tamarack (Picea–Larix laricina) bogs, aspen (Populus) and moist spruce–birch (Betula) forests, and speckled alder (Alnus rugosa) and willow (Salix) stands along stream banks (2, 87, 91). In Rhode Island, they are the most abundant species breeding in red maple swamps (93). Less common in shrub wetlands.
Suitable habitat often has a developed layer of moss and an uneven forest floor (94, 95, 96, 97). In New Hampshire, the number of shrub stems (> 1 m in height and < 8 cm diameter-at-breast-height [DBH]), low canopy height, high foliar density in the vertical layer between 2.0–2.5 m, and perch trees characterized male territories (98). In British Columbia and Saskatchewan, most common on steep slopes within deciduous forest with dense birch understory, or riparian willow and alder shrubbery (99, 41). In Alberta, often found in deciduous stands with a wild rose (Rosa) and beaked hazel (Corylus cornuta) understory. Higher densities are found in locations with older deciduous forests near small streams located within larger deciduous stands (100). Also found in post-harvest forest stands but density is reduced compared to unharvested stands (101). In Manitoba, deciduous stands with beaked hazel and willow understory. In New Brunswick, mixed wood stands with mossy understory and wild raisin (Viburnum nudum). Sites were typically marshier and wetter in New Brunswick in comparison to Alberta and Manitoba, although water features were regularly present at breeding sites (Roberto-Charron, personal communication). Also in younger, cut-over forests and forest edge. Heterogeneous second-growth (early successional) mixed coniferous–deciduous forests in northern Wisconsin (102). Maine and New Hampshire, early successional stands and deciduous understory of mature forests (103, 104). Presence correlated with number of deciduous woody stems < 10 cm dbh and > 4.5 m tall in regenerating clearcut spruce–fir (Picea–Abies)/hardwood forests of Maine (105).
Fitness related parameters such as pairing success and fledging success (at least one young) did not differ between red maple swamps and an early successional (25 yr post harvest) forest stand in New Hampshire. Similar vegetation characteristics were found between the two habitat types although the shrub layer composition differed, suggesting that structure rather than species composition influences reproductive performance (104). In Alberta, no reproductive differences were found between territories in post-harvest (< 30 yr old stands) and unharvested forests (101).
Also in open areas formed by natural disturbances. In Quebec, found at 43% of survey stations in a boreal mixed-wood forest characterized by natural disturbance, compared to 21% of stations in adjacent industrial timberland (106). Frequently found in small treefall gaps within large mature forest stands in Maine (107), and small canopy gaps (0.1-0.2 ha) within a forested landscape in Vermont (108) and New Hampshire (Reitsma et al., unpublished data).
In the Great Lakes/St. Lawrence River valley, one of the most common warblers in eastern hemlock–white pine–red pine (Tsuga canadensis–Pinus strobus–Pinus resinosa) forests that have a maple–birch–beech (Acer–Betula–Fagus grandifolia) component (2). In Vermont, common in red spruce-northern hardwood forests, especially near natural or created ecotones, but absent from hardwood forests; low numbers detected in lowland conifer swamps (109). More abundant in old than young aspen forests in Alberta (110, 111). In the Allegheny Mountains of western Maryland and northwestern West Virginia, relative abundance positively correlated with foliage density 0.3–1.0 m above ground, forest moisture index, tree basal area, and size of forest fragment; negatively correlated with mean canopy height and percentage ground cover based on responses from point count surveys (112). Understory foliage density, forest moisture index, and tree basal area were the most important predictors (112, 113).
In Pennsylvania, at elevations > 457 m, in areas with cool summer temperatures and above-average precipitation (92). Up to 900 m elevation in New York and New Hampshire (114, 14). Rhododendron (Rhododendron) thickets and streamside vegetation within mountains in southern United States (2, 55) and found in high densities in areas where natural disturbance has caused extremely thick growth of Rhododendron and Mountain Laurel (Merker, personal observation). At higher elevations in southern part of range (> 650 m in West Virginia, > 1,160 m in Kentucky, > 1,400 m in Georgia, up to 1,000–1,900 m in North Carolina; 115, 14, 54, 55).
Habitat in Nonbreeding Range
Habitat in Migration
Found in shrubbery, bushes and vine tangles near edge of parks, villages, and cities, thickets of stream and woodland edges, swamps, and willow trees (11). Brushland, second-growth woodlands, and along edges of timbered lowlands and watercourses during spring migration in southern Minnesota (13). During spring migration in Ohio in shrub layer of upland and lowland forests with preference for spicebushes (Lindera benzoin) within swamp forest (M. B. Trautman in 14). Very habitat-specific during spring migration in North Carolina compared to 18 other warblers; 76.5% of foraging birds observed in one (floodplain forest) of 7 habitat types (116). Forests, undergrowth and thickets near water in Texas (15). Coastal, riparian, and urban areas and dry and wet forests on Caribbean Islands (74). In Mexico, low to mid-story vegetation within humid to semi humid forest, swamp forest, and forest edge, sea level to 2,500 m elevation (61, 5). Up to 1,500 m in open forest, second-growth, and scrub habitats in Honduras; more common on Pacific slope than Caribbean slope (62). Captured infrequently in young and old second-growth forest, and low (50–75 m) and mid-elevation (1,000 m) primary forest at La Selva, Costa Rica (117). Several birds observed in black mangrove forests in western Panama (118).
Habitat in Overwintering Range
Dense undergrowth of submontane cloud and rain forests, early to mid-secondary woodland growth, clearings, and shrubby forest edge 1,000–2,100 m (119, 60, 16). Also coffee plantations, hedgerows, and other semi-open areas (120). Abundant and widespread in Colombia, avoiding the coast and eastern lowlands; most common in mountains and foothills (500–3,150 m; 121, 59). In Ecuador and Peru, abundant on eastern slope of Andes and adjacent lowlands, 300–1,750 m, occasionally to 3,000 m (59).
In Ecuador (Benham et al., unpublished data), found along eastern slope of the Andes, between 1,000–1,500 m, in primary forest, second growth (early and late), forest edges and scrub habitats; observations of both sexes in Ecuador were most frequent in second growth (46%). Older males (36%) found in primary forest more often than females (3%) and younger males (6%). Females observed in scrub (23%) and forest edges (23%) more frequently than males (2% scrub, 13% scrub).
Joins mixed-species flocks during the nonbreeding season, males at higher rates than females, older individuals at higher rates than younger birds (Hallworth et al., unpublished data). Use of mixed-species flocks increases with elevation (122).
In Colombia, where abundant during the nonbreeding season, Céspedes and Bayly (122) found relative densities were higher in mature forest than in secondary forest or shade coffee. Most abundant between 1,000 and 2,200 m with preference for humid, forested regions.