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Black-throated Blue Warbler

Setophaga caerulescens

Order:
Passeriformes
Family:
Parulidae
Sections

Diet and Foraging

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Figure 3. Black-throated Blue Warbler foraging.

Black-throated Blue Warblers usually snatch their insect prey from a leaf, while hovering or flying past. Drawing by J. Zickefoose.

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Adult male Black-throated Blue Warbler foraging.

When foraging, both sexes visually search leaf surfaces, branches, and twigs, tree boles, and surrounding air spaces by moving rapidly through dense foliage. Prey are taken primarily from the under-surfaces of leaves.

© Jay McGowan, New York, United States, 15 May 2013
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Adult female Black-throated Blue Warbler with spider.

In the breeding season, Black-throated Blue Warblers are primarily insectivorous, feeding extensively on Lepidoptera larvae and adults, crane flies and other adult Diptera, other arthropods, spiders, and small snails.

© Frank Salmon, Florida, United States, 26 April 2017
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Adult male Black-throated Blue Warbler with food items.
© Jory Teltser, Maine, United States, 2 July 2016
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Adult female Black-throated Blue Warbler with berry.

In winter, primary foods include some Lepidoptera larvae, leaf hoppers, beetles, flies, and small berries and fruits. Also feeds at flowers, possibly for nectar and/or insects.

© Steve Raduns, Florida, United States, 19 October 2016

Feeding

Main Foods Taken

Breeding period. Insectivorous, feeding extensively on Lepidoptera larvae and adults, crane flies (Tipulidae: Diptera) and other adult Diptera, spiders and other arthropods, and small snails (Robinson and Holmes 1982, Rodenhouse and Holmes 1992, RTH).

Overwintering period. Some Lepidoptera larvae, leaf hoppers, beetles, flies, and small berries and fruits (Wetmore 1916a, RTH); also feeds at flowers, possibly for nectar and/or insects (RTH; J. M. Wunderle, personal communication). In Dominican Republic, feeds frequently on honeydew excretions from scale insects (Latta et al. 2001).

Microhabitats for Foraging

Breeding period. Forage from the ground to high in the canopy, but mainly in the lower to mid strata, with males foraging on average higher than females (5.9 m ± 3.8 SD and 3.3 m ± 3.0 SD, respectively; Holmes et al. 1986). Foraging is more concentrated at shrub and lower canopy strata than other coexisting species, which may contribute to ecological segregation (Holmes et al. 1979b). Based on studies in New Hampshire, 71–79% of arthropod prey are obtained from foliage, 4–13% from branches and twigs, 6–8% from the air, and < 1% from the ground (Holmes et al. 1979b, see also Holmes and Schultz 1988). Prey are taken primarily from the undersurfaces of leaves, with 82% of all foraging maneuvers directed toward foliage (Holmes and Schultz 1988; see Figure 3). In laboratory experiments, learned to locate and capture prey more proficiently from lower leaf surfaces than did Black-throated Green Warblers (Setophaga virens; Whelan 1989a, Whelan 2001). However, individuals shift readily among prey types and surfaces examined, taking advantage of changes in prey availability (RTH).

Overwintering period. Few quantitative data, but food searching behavior appears similar to that in the breeding season (RTH). In Jamaica, foraging height averaged 4.5 m ± 4.0 SD (n = 152), and most foraging attacks were directed towards prey on broad-leaved foliage (46%), with the remainder on twigs (13%), air (17%), ground (15%), and fruit and flowers (8%; n = 350, Lack and Lack 1972). A single male in Ecuador attacked prey from live foliage of trees (68%), and epiphytes (11%), live leaf petioles (13%), and in the air (8%), (n = 38 observations, Martin et al. 2004d). In shade-coffee plantations, forage more frequently among the foliage of overstory trees (mostly Inga) than among the coffee bushes (Wunderle and Latta 1998, Jirinec et al. 2011).

Food Capture and Consumption

Forage alone, although members of a pair sometimes forage near one another.

Breeding period. Males spend 30–32% of daylight hours foraging, plus another 19–20% when they both forage and sing (Black 1975). Females forage 50–70% of the time during nest building and egg laying, declining to only 22% during incubation, but then increasing to 70–80% during feeding of nestlings (Black 1975). Males forage at higher rates when feeding nestlings and fledglings than during the incubation period, although the rates at which they attack prey do not differ between the time periods (Dobbs et al. 2007). Foraging behavior also varies with population density. Males with experimentally reduced neighbor density spent proportionally more time foraging than control males when their social mates were building nests, laying eggs, and incubating (Sillett et al. 2004); males with experimentally reduced neighbor density also reduced their use of aerial attack maneuvers compared to control males (Dobbs et al. 2007).

When foraging, both sexes visually search upper and especially lower leaf surfaces, branches and twigs, tree boles, and surrounding air spaces by moving rapidly through dense foliage (Robinson and Holmes 1982, Robinson and Holmes 1984, Holmes et al. 1986). At these times, they change perches at an average rate of 26 times/min, hopping slightly more often than flying (Robinson and Holmes 1982). Their search radius (the distance over which they attack potential prey) averages 53.0 cm ± 4.0 SD (n = 558), and they attack prey at a rate of 2.2/min ± 0.2 SE (n = 142 foraging sequences; Robinson and Holmes 1982). The most frequent prey capture method is to snatch prey from a substrate, usually a leaf, while hovering or flying past (65%); secondly (35%), they glean prey from nearby substrates while standing on the vegetation (Robinson and Holmes 1984). Unlike other species in northern hardwood forests, they do not change their relative use of foraging maneuvers or search tactics among tree species or strata, suggesting more stereotyped foraging behavior (Robinson and Holmes 1984). In laboratory experiments, their foraging behavior changes with leaf shape and position in relation to available perches (Whelan 1989b, Whelan 2001), suggesting that plant morphology influences their foraging success. Capture methods and substrates searched shift rapidly with changes in food availability, and individuals may focus on one abundant prey type during the period that it is available (NLR).

Overwintering period. Few quantitative data available. From studies in Jamaica (Lack and Lack 1972), 72% of foraging maneuvers were made by perched birds (presumably gleans), 18% in the air, 8% by hovering, and 2% by fluttering from a perch (n = 350). If these data are representative, these birds apparently switch from primarily gleaning insectivorous prey from leaf undersurfaces in summer to capturing prey from foliage during the overwintering period. Also, obtain nectar from flowers and pluck berries and small fruits from understory shrubs (Wetmore 1916a, Wunderle 1995, Martin et al. 2004d, RTH). In shade coffee plantations in the Dominican Republic, foraged mostly in the overstory tree canopy (mostly Inga), where it mostly gleaned prey from leaves, but also hovered and probed a variety of substrates, including flowers, bark, and lichens (Wunderle and Latta 1998). When foraging among the foliage of coffee, only 14% of foraging maneuvers were directed towards prey on leaves (Wunderle and Latta 1998). Studies in Jamaican coffee plantations show that foraging by this species, in conjunction with that of other co-occurring, mostly overwintering Neotropical migrants, significantly reduce the numbers of foliage-eating insects, particularly the coffee berry borer, Hypothenemus hampei (Kellermann et al. 2008; see also Sherry et al. 2016).

Diet

Major Food Items

Breeding period. Similar to that of other co-occurring insectivorous passerines in northern hardwood forests (Robinson and Holmes 1982). Based on frequencies of occurrence in 58 stomach samples from New Hampshire breeding grounds in June and early July, diet comprised of larval Lepidoptera (28%), Coleoptera (50%), adult Diptera (12%), and other arthropods (including Homoptera, Hymenoptera—10%). From observations of 109 prey taken at this same site, larval Lepidoptera constituted 81%, adult Lepidoptera 14%, Diptera 2%, and spiders 4% (Robinson and Holmes 1982).

Overwintering period. Reported taking 76% animal food (leafhoppers, weevils, flies, and spiders) and 24% vegetable matter (mostly seeds of small berries, especially Miconia) in Puerto Rico (Wetmore 1916a) and 95% insect and 5% fruit in Jamaica (Lack and Lack 1972). In Jamaica, seen feeding on adult moths, small lepidopteran larvae, spiders, and small berries and fruits when available; also sugar water from hummingbird feeders, and processed sugar, cheese, and crumbs from feeding stations (RTH). In shade-coffee plantations in Jamaica, based on 1,908 prey items from 23 stomach (emetic) samples obtained between 11–17 March 2000, diet consisted of 42.8% plant lice (psyllids: Hemiptera), 19.9% bark lice (Psocoptera), 15.8% ants (Hymenoptera), 11.4% beetles (Coleoptera), and 3.5% parasitic wasps (Hymenoptera), with smaller numbers of spiders, lacewings, moths, caterpillars, midges, and other small insects (T. W. Sherry, unpublished data; see also Sherry et al. 2016). Also, in shade-coffee plantations in Jamaica, feed extensively on the coffee berry borer (Hypothenemus hampei), a major pest, thus providing an important ecosystem service (Kellermann et al. 2008, Sherry et al. 2016).

In low-elevation forests in Puerto Rico, foraging attacks were directed toward arthropods (98% for males, 100% for females); at higher elevations, individuals fed more on fruits (13% for males, 16% for females) and at flowers, possibly for nectar (8% for males, 20% for females; Wunderle 1995). In the Dominican Republic, reported to feed extensively on honeydew from scale insects on Bursera simaruba trees (Latta et al. 2001). Recorded taking insects from spider webs on the breeding grounds (RTH), on fall migration (Brooks 1986), and on the overwintering grounds (RTH).

Food Selection and Storage

No information.

Nutrition and Energetics

No studies available on nutrition.

Population energetics was studied in New Hampshire using a time activity-metabolic estimate method (Black 1975, Holmes et al. 1979a). Estimated daily energy expenditure ranged from 4.04 to 4.93 kJ, varying among the periods of the nesting cycle, and totaled 4,004 kJ/ha for the summer season (Holmes et al. 1979a). Net production (energy content represented by mass of fledged young) was estimated at 36 kJ/ha, giving a total of energy assimilated over the breeding season of 4,040 kcal/ha. Because of its relatively low breeding density, this estimate of population energy flow was considerably lower than those of two co-occurring forest passerine populations, Red-eyed Vireo (Vireo olivaceus) and Least Flycatcher (Empidonax minimus) (Holmes et al. 1979a).

Metabolism and Temperature Regulation

Basal metabolic rate was measured as 3.49 cc O2/g h ± 0.15 SE, within a thermoneutral zone ranging from 24–31°C (Black 1975). The relationship between oxygen consumption and temperature below 24°C (the minimum critical temperature) is described by the regression: M = 0.184T ± 7.873, where M = oxygen consumption in cc/g of live weight per hour, and T = ambient temperatures in °C (Black 1975).

Drinking, Pellet-Casting, and Defecation

No information.

Recommended Citation

Holmes, R. T., S. A. Kaiser, N. L. Rodenhouse, T. S. Sillett, M. S. Webster, P. Pyle, and M. A. Patten (2017). Black-throated Blue Warbler (Setophaga caerulescens), version 3.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.btbwar.03