Diet and Foraging

Main Foods Taken

Feeds almost exclusively on insects caught by hawking from the air or gleaned from foliage of trees and shrubs (Tarof and Ratcliffe 2004 Tarof, S. A. and L. M. Ratcliffe. (2004). Habitat characteristics and nest predation do not explain clustered breeding in least flycatchers (Empidonax minimus). Auk 121 (3):877-893. Close , JVB). Fruits and seeds taken occasionally.

Microhabitat For Foraging

Forages at heights ranging from 1–15 m, from top of shrub stratum up to leafy canopy of forest overstory (Breckenridge 1956a Breckenridge, W. J. (1956a). Measurements of the habitat niche of the Least Flycatcher. Wilson Bulletin 68:47-51. Close , Johnston 1971b Johnston, D. W. (1971b). Niche relationships among some deciduous forest flycatchers. Auk 88:796-804. Close , SAT). In New Hampshire, most foraging at heights of 12–15 m, where vegetation is least dense (Sherry 1979 Sherry, T. W. (1979). Competitive interactions and adaptive strategies of American Redstarts and Least Flycatchers in a northern hardwoods forest. Auk 96:265-283. Close ). Forages lower in canopy with increasing wind speed and cooler temperatures (Pohajdak 1988 Pohajdak, G. C. (1988). Feeding guilds, diets and foraging behavior of insectivorous passerines in a riparian habitat in Manitoba. Ph.D. dissertation, University of Manitoba, Winnipeg, MB, Canada. Close ).

Generally broad-niched with respect to tree-species use. In New Hampshire, prefers yellow birch (Betula allegheniensis) and avoids beech (Fagus grandifolia), sugar maple, white ash, and conifers (Picea rubens, Tsuga canadensis); slight preference for yellow birch probably attributable to greater densities of insects (Holmes and Robinson 1981 Holmes, R. T. and S. K. Robinson. (1981). Tree species preferences of foraging insectivorous birds in a northern hardwood forest. Oecologia 48:31-35. Close ). In Wisconsin, Least Flycatchers foraged in tree species in proportion to abundance and not to foraging success, except pines (Pinus spp.) were used less than expected (Rogers 1985a Rogers, C. M. (1985a). Foraging success and tree species use in the Least Flycatcher. Auk 102:613-620. Close ). Most foraging bouts initiated from branches in mid- and lower portions of trees; dead branches most frequent type of perch (76.7%), followed by live branches (18.6%) and inanimate objects (4.7%; Via 1979 Via, J. W. (1979). "Foraging tactics of flycatchers in southwestern Virginia." In The role of insectivorous birds in forest ecosystems., edited by J. G. Dickson and et al, 191-202. NY: Academic Press. Close ).

Foraging microhabitat on wintering grounds probably similar to breeding grounds; forages from 0–20 m, depending on habitat structure. Foraging flights typically from open area into open pocket in forest (Rappole and Warner 1980 Rappole, J. H., and D. W. Warner (1980). Ecological aspects of migrant bird behavior in Veracruz, Mexico. In Migrant birds in the Neotropics: Ecology, Behavior, Distribution, and Conservation (A. Keast and E. S. Morton, Editors). Smithsonian Institution Press, Washington, DC, USA. pp. 353–393. Close ).

Food Capture And Consumption

Hawking or flycatching are the most common foraging tactics (81.0%), followed by gleaning (including hover-gleaning) from foliage (19.0%); midair flycatches characterized by short sallies averaging 1.2 m (Via 1979 Via, J. W. (1979). "Foraging tactics of flycatchers in southwestern Virginia." In The role of insectivorous birds in forest ecosystems., edited by J. G. Dickson and et al, 191-202. NY: Academic Press. Close ). Least Flycatchers spend less time “hawking” for insect prey than other North American Tyrannid flycatchers (Murphy 1989 Murphy, M. T. (1989). Life-history variability in North American breeding tyrant flycachers: Phylogeny, size or ecology? Oikos 54:3–14. Close ). In Wisconsin, foraging success (proportion of perch changes that resulted in a foraging attempt) greater in paper birch (Betula papyrifera) than in either maple (Acer spp.) or oak (Quercus spp.), but differences are small and are probably due to differences in prey density among tree species (Rogers 1985a Rogers, C. M. (1985a). Foraging success and tree species use in the Least Flycatcher. Auk 102:613-620. Close ). At Delta Marsh, Manitoba, Least Flycatchers hawked more and gleaned less often during warm sunny weather than on cool overcast days (Pohajdak 1988 Pohajdak, G. C. (1988). Feeding guilds, diets and foraging behavior of insectivorous passerines in a riparian habitat in Manitoba. Ph.D. dissertation, University of Manitoba, Winnipeg, MB, Canada. Close ). Foraging by hawking and gleaning also observed on wintering grounds (Rappole and Warner 1980 Rappole, J. H., and D. W. Warner (1980). Ecological aspects of migrant bird behavior in Veracruz, Mexico. In Migrant birds in the Neotropics: Ecology, Behavior, Distribution, and Conservation (A. Keast and E. S. Morton, Editors). Smithsonian Institution Press, Washington, DC, USA. pp. 353–393. Close ).

Major Food Items

In summer, feeds almost exclusively on arthropods (Tarof and Ratcliffe 2004 Tarof, S. A. and L. M. Ratcliffe. (2004). Habitat characteristics and nest predation do not explain clustered breeding in least flycatchers (Empidonax minimus). Auk 121 (3):877-893. Close , JVB). Winter diet not quantified but probably also primarily insectivorous.

Quantitative Analysis

Beal (Beal 1912 Beal, F. E. (1912). Food of our important flycatchers. Biological Survey Bulletin 44. Close ) examined 177 flycatcher stomachs collected from Apr–Sep over 13 states, the District of Columbia, Ontario, and Nova Scotia. Animal matter comprised 97.8% and vegetable matter 2.2% of diet. Insect prey (in order of importance): Hymenoptera (both ants and parasitic species: 41.1%), Coleoptera (21.4%), Diptera (11.3%), Hemiptera (11.1%), Lepidoptera (adults and caterpillars: 7.3%), Orthoptera (2.6%), spiders (2.1%), and others (Odonata, Ephemeroptera: 1.0%). The small amount of vegetable matter present comprised a few fruits (e.g., Rubus spp., Sambucus canadensis) and seeds (Phleum pratensis, Chaetochloa sp.). A list of all species of insects and seeds observed in flycatcher stomachs given in Beal (Beal 1912 Beal, F. E. (1912). Food of our important flycatchers. Biological Survey Bulletin 44. Close ; see also Johnston 1971b Johnston, D. W. (1971b). Niche relationships among some deciduous forest flycatchers. Auk 88:796-804. Close ).

At Delta Marsh, Manitoba, midges (Chironomidae) were the most common item in stomachs of 55 Least Flycatchers collected from late May–early Jul (Pohajdak 1988 Pohajdak, G. C. (1988). Feeding guilds, diets and foraging behavior of insectivorous passerines in a riparian habitat in Manitoba. Ph.D. dissertation, University of Manitoba, Winnipeg, MB, Canada. Close ). Diets of Least Flycatchers and Eastern Wood-Pewees overlapped on 46% of food taxa but overlap with Great Crested Flycatchers (Myiarchus crinitus) only about 28%. Least Flycatchers fed on smaller prey than Eastern Wood-Pewees or Great Crested Flycatchers (Johnston 1971b Johnston, D. W. (1971b). Niche relationships among some deciduous forest flycatchers. Auk 88:796-804. Close ).

Darveau et al. (Darveau et al. 1993 Darveau, M., G. Gauthier, J. L. DesGranges and Y. Mauffette. (1993). Nesting success, nest sites, and parental care of the Least Flycatcher in declining maple forests. Canadian Journal of Zoology 71:1592-1601. Close ) examined stomach contents of 30 nestling Least Flycatchers from Quebec and found Coleoptera constituted 29% (by volume) and Lepidoptera larvae 26% of food remains. Data on Malaise trap arthropod sampling are consistent with diet analysis (Tarof and Ratcliffe 2004 Tarof, S. A. and L. M. Ratcliffe. (2004). Habitat characteristics and nest predation do not explain clustered breeding in least flycatchers (Empidonax minimus). Auk 121 (3):877-893. Close 4). Direct identification of prey delivered by adults at the nest also revealed a preponderance of Lepidoptera (39%; larvae and adults) plus many Diptera (19% of identifiable prey; Darveau et al. 1993 Darveau, M., G. Gauthier, J. L. DesGranges and Y. Mauffette. (1993). Nesting success, nest sites, and parental care of the Least Flycatcher in declining maple forests. Canadian Journal of Zoology 71:1592-1601. Close ). Small quantities of Hymenoptera, Arachnida, Hemiptera, and Mecoptera have been observed in both feeding deliveries and nestling stomachs (Darveau et al. 1993 Darveau, M., G. Gauthier, J. L. DesGranges and Y. Mauffette. (1993). Nesting success, nest sites, and parental care of the Least Flycatcher in declining maple forests. Canadian Journal of Zoology 71:1592-1601. Close ). Diet of nestlings varies with age; at Delta Marsh, Manitoba, midges (Chironomidae) are most important prey identified during nest visits by adults, increasing from 62.0% of identifiable prey at 2 d to 83.4% at 11 d after hatching (Figure 2). In contrast, Geometridae larvae (Lepidoptera) form 25.7% of diet of 2-d-old nestlings but less than 5% of diet of nestlings older than 5 d (Figure 2; Briskie 1985 Briskie, J. V. (1985). Growth and parental feeding of Least Flycatchers in relation to brood size, hatching order and prey availability. Master's Thesis, Univ. Manitoba, Winnipeg. Close , JVB).

No specific information available for this species.

No specific information available for this species.

Nocturnal thermoregulatory costs for Least Flycatchers in New Hampshire during summer estimated at 2.8 times standard metabolic rate (4.27 ± 0.13 cc O²/g/h; Holmes et al. 1979a Holmes, R. T., C. P. Black and T. W. Sherry. (1979a). Comparative population bioenergetics of three insectivorous passerines in a deciduous forest. Condor 81:9-20. Close ). Daily energy expenditure (DEE) of Least Flycatchers is greater than that of Red-eyed Vireos (Vireo olivaceus) or Black-throated Blue Warblers (Dendroica caerulescens), largely because flycatchers fly more while foraging and have a lower critical temperature (32°C) at night (Holmes et al. 1979a Holmes, R. T., C. P. Black and T. W. Sherry. (1979a). Comparative population bioenergetics of three insectivorous passerines in a deciduous forest. Condor 81:9-20. Close ). Time and energy expenditures of male and female flycatchers approximately equal, with variation due to different roles in breeding activities (e.g., males sing more, only females incubate). Both male and female flight time and DEE increase dramatically with hatching of young, suggesting foraging to feed young is a particularly demanding and costly activity. Estimated DEE lowest for both sexes in prenesting stage (males: 1.299 kcal/g/d; females: 1.271 kcal/g/d); peak energy demand occurs early Jul, shortly after young fledged (males: 1.624 kcal/g/d; females: 1.695 kcal/g/d). A detailed time budget and estimates of DEE for male and female flycatchers over nesting cycle are given in Holmes et al. (Holmes et al. 1979a Holmes, R. T., C. P. Black and T. W. Sherry. (1979a). Comparative population bioenergetics of three insectivorous passerines in a deciduous forest. Condor 81:9-20. Close ).

No specific information available for this species.