Food Habits

Main Foods Taken

Insects and other arthropods; may take wild fruits occasionally (Stevenson and Anderson 1994).

Microhabitat For Foraging

On small islands off Maine, summer observations of foraging showed small limbs preferred to large limbs, tips and dead limbs for both deciduous and coniferous trees (Morse 1973). In Utah, foraging observed between 1–55 ft [0.3–16.8 m] (top of vegetation), never on ground, mostly between 6–8 m, mean 7.3 m, n = 2,195 (Frydendall 1967). May–Jun foraging observations in Wyoming showed Yellow Warblers foraged in height classes ranging from 0–0.6 m to 4.9–9.8 m (n = 56), with most observations in classes 1.2–2.4 m (n = 17) and 2.4–4.9 m (n = 15); Jan–Feb observations in Nayarit, Mexico, showed warblers foraging in height classes 1.2–2.4 m to >9.8 m (n = 54), with most observations in classes 4.9–9.8 m (n = 14) and >9.8 m (n = 30; Hutto 1981). Based on 25,000 s observation in Manitoba, males foraged higher (mean 7.1 m, n = 13,903 s) than females (mean 4.4 m, n = 9,483 s) and more exposed (= further out on branches) and in higher vegetation; foraging height difference between males and females greatest before 7 Jun, during pre-egg-laying and period of territory establishment, suggesting males foraged in conspicuous manner to promote territory establishment and maintenance (Busby and Sealy 1979).

Adult seen “hawking” (sallying after; see below) flying insects over Fish River, Alaska (Kessel 1989).

Food Capture And Consumption

Captures insects by gleaning (picking food from a surface while perched), sallying (flying out after airborne prey) or hovering (picking food from a surface while in flight). On breeding grounds in Utah, 2,255 foraging observations categorized as 95.5% gleaning, 1.7% sallies, 2.8% hovering (Frydendall 1967). On breeding grounds in Wyoming during May–Jun, 186 foraging actions categorized as glean 127, sally 48, hover 11; foraging substrate included ground 4, bark 56, foliage 78 and air 48; on nonbreeding grounds in Nayarit, Mexico, during Jan–Feb, 58 foraging actions categorized as glean 42, sally 12, hover 4; foraging substrate included ground 1, bark 2, foliage 43, air 12 (Hutto 1981).

Foraging actions monitored in Ontario, Montana, and Colorado (n = 373) described as 62% perch actions (i.e., prey capture while perched) (and 38% aerial (i.e., prey capture while in flight; including hover-gleaning, outward-striking and aerial-hawking); perch-to-perch attack distance 0.8 m (range 0–24.6); foraging rate, 5 attacks/min (range 0.34–20; height of bird, 4.9 m (range 0–14.9) in 7.5 m tree (range 0.3–16.8); for the nonbreeding season in Yucat·n, Mexico, and Panama, both wintering Yellow Warblers (n = 53) and resident Mangrove Warblers (n = 292) behaved generally similarly (Wiedenfeld 1992): for Yellow Warbler, foraging consisted of 81% perch actions and 19% aerial actions, perch-to-perch attack distance 0.7 m (range 0–1.8), foraging rate, 5 attacks/min (range 0.90–20, height of bird 6.4 m (range 0.5–16.5) in 9.8 m tree (range 1.2–18.3); for Mangrove Warbler foraging consisted of 76% perch actions and 23% aerial actions, perch-to-perch attack distance 1.1 m (range 0–11.1), foraging rate 4 attacks/min (range 0.60–30, height of bird 6.1 m (range 0–18.3) in 10.7 m tree (range 0.5–19.8). On nonbreeding territories in Chiapas, Mexico, 1.75 attacks/min ± 0.85 SD (n = 70) capturing “large” arthropods, primarily 2-cm caterpillars (Greenberg and Salgado-Ortiz 1994).

Major Food Items

Mostly insects.

Quantitative Analysis

Proportion of insect orders and families in diet varies with location. In Manitoba study, May–Aug, adult midges (Chironomidae) comprised about 57% of diet (n = 87 stomach contents); next in abundance were Lepidoptera larvae (especially Geometridae), Coleoptera, Hemiptera, Homoptera, and Hymenoptera (Busby and Sealy 1979). In Utah study during breeding season, Hymenoptera most numerous, then Diptera, Hemiptera, and Coleoptera (n = 98; Frydendall 1967). For 5 birds from cankerworm-infested orchard in Illinois during Jul, stomach contents 67% cankerworms (Lepidoptera; Geometridae), 23% beetles (including Aphodius, Psenocerus, and Telephorus spp.), 6% spiders, 2% Hymenoptera, and 1% Hemiptera (Graber et al. 1983). One of 10 wintering specimens from Panama had been feeding on nectar and pollen of Inga sp. tree (Morton 1976). No studies of diet during nonbreeding season.

In general, takes an insect in proportion to its availability as measured in sweep-net samples; sexes forage at different heights (males higher), females gleaned less and hovered more than males (Busby and Sealy 1979).

Not known to store food.

No information.

No information.

No information.