Canada Warbler Cardellina canadensis
Version: 2.0 — Published May 7, 2020
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Diet and Foraging
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Main Foods Taken
Microhabitat for Foraging
Lower tree branches and shrubs, aerial; occasionally forages on ground (96). Uses both coniferous and deciduous trees, but in northern Wisconsin both sexes foraged more frequently in conifers and less frequently in hardwoods compared to availability and sympatric wood warblers (102). Used conifers for 36% of 884 foraging maneuvers in New Hampshire (157). Nearly all foraging done below 5 m (97, 90, 99); 3.8 m (range 2.6–5.2) in New Hampshire (157). Always foraged within shade in Wisconsin (28). In northern Wisconsin, males foraged lower in vegetation than sympatric Nashville Warbler (Leiothlypis ruficapilla) and Chestnut-sided Warbler (Setophaga pensylvanica), but higher than Mourning Warbler (Geothlypis philadelphia) (102). Similar to other wood-warblers, females tended to forage lower in vegetation than males (females 3.18 m ± 0.27 SD [range 1.0–8.3, n = 39] and males 4.06 m ± 0.25 SD [range 0.3–23.0, n = 122]; 102). Most frequently foraged on red-osier dogwood (Cornus stolonifera) and young birch trees within understory in British Columbia (99).
Of 180 foraging observations on 19 individuals during fall migration in Ontario, most were gleaning from shrubs, sapling foliage and branches, and inner branches of trees, 1.5–7 m high (133). During October and early November in Panama, foraging birds usually associated with antwren foraging flocks in moist and dry forests (158).
Lower and upper layers of vegetation within forests and second growth (119).
Food Capture and Consumption
Variety of foraging techniques, including flycatching, sallying, hover gleaning, foliage gleaning, and ground gleaning. Equal to American Redstart (Setophaga ruticilla) in flycatching ability. Based on 1.3 h of observation, males and females in northern Wisconsin used foraging methods involving flight (mostly hover and sally) in approximately 70% and 43% of prey pursuits, more frequently than sympatric wood warblers (102). In New Hampshire, used primarily gleaning and hovering (as opposed to flycatching) during 884 foraging maneuvers (157). During 100 observations in New York, used aerial hawking, climbing hop with flutter, and methodical search (gleaning) on low branches (159). Sometimes slams wiggling insect against side of branch after capture (160). While foraging, travels most frequently by hopping along branches (102). Moves faster while foraging (0.40 and 0.33 hops and flights/s for males and females, respectively) than sympatric Mourning Warbler and Chestnut-sided Warbler (102). Flight distances between substrates while foraging; 0.98 m ± 0.04 SD (n = 210) for males and 0.85 m ± 0.10 SD (n = 33) for females (102). On overwintering grounds, very active foliage-gleaner within mixed-species flocks, sometimes making short aerial sallies (60). Can move so quickly during foraging that observers have described their behavior as “bouts of animated flycatching” (91), “a bundle of restless activity” and “violent activity” (160).
Major Food Items
Mostly winged insects: mosquitoes (Culicidae), flies (Diptera), especially Tipulidae, moths (Lepidoptera), beetles (Coleoptera), small hairless caterpillars (Lepidoptera), and spiders (Arachnida) (12, 14). Observed eating oak scales (Kermes spp.; 161). One female observed catching worms, flies, and mosquitoes during incubation recesses in Michigan (160). Observed flycatching mosquitoes on the wing (13). Stomach contents of birds in Maryland contained ants (Formicoidae) and bees (Family Andrenidae, Andrena spp., Halictus spp.; 162). Flies, hymenopterous insects, beetles, larvae in 3 specimens examined in Wisconsin (F. H. King in Bent ). In coastal Rhode Island, 2 of 5 birds had fruit (all 5 had insects) in fecal samples during autumn migration (24.0% ± 19.1 SD fruit in samples; 163). Five locusts (Cicadidae) and 29 other insects in one stomach examined in Nebraska (S. Aughey in Bent ). Stomach contents of 2 birds during fall migration in Ontario contained beetles and 1.5-mm-wide snails (133). Insects in winter (60), but no detailed data available.
Food Selection and Storage
Nutrition and Energetics
Metabolism and Temperature Regulation
Drinking, Pellet-Casting, and Defecation
Limited information on drinking or defecation. One female observed with beak lifted, nibbling raindrops dripping off leaf tip (160).