Least Flycatcher

Distribution and Abundance

• BBS Map
• Breeding range across Canada and north-central and northeastern United States; also Appalachian Mountains.
• Breeding densities highest in Adirondack Mountains of New York and parklands of Manitoba, Saskatchewan and Alberta. 
• Historically, this species has been declining and disappearing from some former breeding areas in eastern North America (Holmes and Sherry 1988).
• Winters in Mexico and Central America.

Habitat

• Found in semi-open, second-growth, and mature deciduous and mixed woods; occasionally conifer groves, burns, swamp and bog edges, orchards, and shrubby fields. More abundant in dense and closed canopy forests away from disturbances and openings (DellaSala and Rabe 1987, Martin 1994); but also found near open spaces, such as forest clearings and edges, water, roads, and cottage clearings (Breckenridge 1956, Peck and James 1983). Found in more densely vegetated habitats than Eastern Wood-Pewees but in less densely vegetated forests than those favored by Acadian Flycatchers (Hespenheide 1971).
• In Wisconsin, 52% of 984 observations from 1995-2000 were in upland hardwood forest, predominately maple, and 17% in upland mixed forest (WSO 2002). In Michigan, of survey observations from 1983-1988, this species was found breeding in both deciduous and mixed forest, and occasionally in stands of half-grown jack pine; preferences were for mesic deciduous forest followed by dry deciduous forest and dry mixed forest (Brewer et al. 1991). Prefers drier woodlands than other Empidonax flycatchers (Walkinshaw 1966). In Quebec, most often associated with areas of high and well-developed canopy and in forests that contain a high proportion of sugar maple (Darveau et al. 1992).
• Forages from top of shrub stratum up to leafy canopy of forest overstory (Breckenridge 1956, Johnston 1971). In New Hampshire, most foraging at heights of 12-15 m where vegetation is least dense (Sherry 1979); prefers foraging in yellow birch and avoids beech, sugar maple, white ash, and conifers; preference for yellow birch probably attributed to greater densities of insects (Holmes and Robinson 1981). In Wisconsin, foraged in tree species in proportion to abundance of tree species, except pines which were used less than expected; foraging success greater in paper birch than in maple or oak (Rogers 1985).
• Nest site located in variety of trees depending on geographic region. In Michigan, of 102 nests, 41 were in maples, 26 in white oaks, 8 in black and red oaks, 7 in aspens and the remainder in a variety of other tree species (Walkinshaw 1966). In Ontario, small trees or saplings selected more than mature trees; species chosen most often were birches (67 nests), maples (30 nests), poplars (27 nests) and then pines (Peck and James 1983). In Quebec, 88.3% of 94 nests were in sugar maple (Darveau et al. 1993). Of 556 nests in Manitoba, 37.6% were in Manitoba maple, 29.9% in green ash, and 27% in sandbar willow.
• On wintering grounds, found in wooded ravines, woodland edges, and brushland in Central America and in humid brush and pasture edges in the Caribbean (Fitzpatrick 1980). In Mexico, observed in both young and old second growth evergreen tropical forest (Rappole and Warner 1980).

Behavior

• Feeds almost exclusively on insects. Fruits and seeds taken occasionally.
• Males sing almost immediately upon arrival on breeding grounds and continue singing until young in most broods are independent and adults begin fall migration (Sealy and Biermann 1983).
• Where territories overlap, Least Flycatchers attack American Redstarts repeatedly throughout the breeding season; flycatchers socially dominant over redstarts (Sherry and Holmes 1988). Least Flycatchers chase most small and medium-sized passerines that approach nest or young. When chasing either conspecifics or heterospecifics, Least Flycatchers produce a loud clatter by rapidly clicking or snapping bill (Davis 1959).
• Territory sizes ranged from 0.03 - 0.38 ha in Ontario (Martin 1960), 0.17 - 0.19 ha in New Hampshire (Sherry 1979), and 0.01 - 0.20 ha in Michigan (MacQueen 1950).
• Despite defense of exclusive territories, most flycatcher territories distributed in dense aggregations leaving adjacent suitable habitat unoccupied (Davis 1959); amount of forest occupied by aggregations ranged from 1.65 - 38.5 ha in Michigan (DellaSala and Rabe 1987). Large open areas near territory aggregations sometimes used as neutral feeding grounds by all flycatchers nesting nearby (MacQueen 1950).
• On wintering grounds, both sexes defend separate territories (Rappole and Warner 1980).

Parasitism and Predation

• Brown-headed Cowbird parasitism rates vary: from 0 of 58 nests in Quebec (Darveau et al. 1993), 5% of 99 nests in Ontario (Peck and James 1983), 9.3% of 54 nests (Walkinshaw 1966) and 11.9% of 143 nests (Southern and Southern 1980) in Michigan. Over a three-year period in southern Manitoba, nest parasitism averaged 2.8% (Briskie et al. 1990). In a continental survey, 39 instances of cowbird parasitism were reported on the Least Flycatcher (Friedmann 1963, Friedmann et al. 1977). In Wisconsin, 4 of 480 confirmed Brown-headed Cowbird observations from 1995-2000 indicated the Least Flycatcher as host (WSO 2002).
• Typically, only cowbirds fledge from parasitized nests (Terrill 1961, Walkinshaw 1966, Briskie and Sealy 1987). The shorter incubation period of the cowbird results in neglect and subsequent death of host eggs after cowbird hatches (Walkinshaw 1961, Briskie and Sealy 1990).
• Low rate of parasitism not due to egg rejection but may be due to aggression of Least Flycatcher adults. Adults bill-snap when approaching or attacking a Brown-headed Cowbird model placed near nest; adults will attack both live and model Brown-headed Cowbirds, occasionally striking head and back of cowbird; responses to cowbird model greater than to model of Fox Sparrow (Briskie and Sealy 1989).
• Predators of Least Flycatcher nests include Red-winged Blackbirds, Gray Catbirds, Common Grackles, American Crows, red squirrels, eastern chipmunks, white-tailed deer, and black rat snake. In Manitoba, nest predation responsible for 81.6% of 103 nest failures (Briskie 1985). In Quebec, 88% of 17 nest failures result of predation (Darveau et al. 1993). Attack on adult and its young by gray squirrels observed (Bent 1942).

Conservation and Management

• Flycatchers respond to logging in large tracts of forest by shifting breeding aggregations away from disturbance and into forest interior (DellaSala and Rabe 1987). Local density correlated positively with area of forest patch size and negatively with isolation between patches; not found in forest patches less than 0.2 ha (Johns 1993). 
• BBS trend results from 1966-2000 (Sauer et al. 2001) in the Northern Spruce-Hardwoods region indicate the Least Flycatcher population has decreased significantly in this region  (-2.3, p=0.00 Trend Graph S28); although not as pronounced, this species is also decreasing in the Great Lakes Transition region (-1.6, p=0.10 Trend Graph S20). Survey-wide (US and Canada), this species has shown a slight, but significant decrease (-0.9, p=0.00 Trend Graph SUR).

References

• Bent, A.C. 1942. Life histories of North American flycatchers, larks, swallows, and their allies. U.S. Nat. Mus. Bull. 179, Washington, D.C. 
• Breckenridge, W.J. 1956. Measurements of the habitat niche of the Least Flycatcher. Wilson Bull. 68:47-51.
• Brewer, R., G.A. McPeek and R.J. Adams, Jr. 1991. The atlas of breeding birds of Michigan. Michigan State University Press, East Lansing.
• Briskie, J.V. 1985. Growth and parental feeding of Least Flycatchers in relation to brood size, hatching order and prey availability. Masters thesis, Univ. Manitoba, Winnipeg.
• Briskie, J.V. and S.G. Sealy. 1987. Responses of Least Flycatchers to experimental inter-and intraspecific brood parasitism. Condor 89:899-901.
• Briskie, J.V. and S.G. Sealy. 1989. Changes in nest defense against a brood parasite over the breeding cycle. Ethology 82:61-67.
• Briskie, J.V. and S.G. Sealy. 1990. Evolution of short incubation periods in the parasitic cowbirds. Auk 107:789-794.
• Briskie, J.V., S.G. Sealy and K.A. Hobson. 1990. Differential parasitism of Least Flycatchers and Yellow Warblers by the Brown-headed Cowbird. Behav. Ecol. Sociobiol. 27:403-410.
• Darveau, M., J.L. DesGranges and G. Gauthier. 1992. Habitat use by three breeding insectivorous birds in declining maple forests. Condor 94:72-82.
• 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. Can. J. Zool 71:1592-1601.
• Davis, D.E. 1959. Observations on territorial behavior of Least Flycatchers. Wilson Bull. 71:73-85.
• DellaSala, D.A. and D.L. Rabe. 1987. Response of Least Flycatchers to forest disturbances. Biol. Conserv. 41:291-299.
• Fitzpatrick, J.W. 1980. Wintering of North American tyrant flycatchers in the Neotropics. Pp. 67-78 in Migrant birds in the Neotropics (A. Keast and E.S. Morton, eds.). Smithson. Inst. Press, Washington, D.C.
• Friedmann, H. 1963. Host relations of the parasitic cowbirds. U.S. Natl. Mus. Bull. 233.
• Friedmann, H., L.F. Kiff and S.I. Rothstein. 1977. A further contribution to knowledge of the host relations of the parasitic cowbirds. Smithson. Contr. Zool. 235, Washington, D.C.
• Hespenheide, H.A. 1971. Flycatcher habitat selection in the eastern deciduous forest. Auk 88:61-74.
• Holmes, R.T. and S.K. Robinson. 1981. Tree species preferences of foraging insectivorous birds in a northern hardwoods forest. Oecologia 48:31-35.
• Holmes, R.T. and T.W. Sherry. 1988. Assessing population trends of New Hampshire forest birds: local vs. regional patterns. Auk 105:756-768.
• Johns, B.W. 1993. The influence of grove size on bird species richness in aspen parklands. Wilson Bull. 105:256-264.
• Johnston, D.W. 1971. Niche relationships among some deciduous forest flycatchers. Auk 796-804.
• MacQueen, P.M. 1950. Territory and song in the Least Flycatcher. Wilson Bull. 62:194-205.
• Martin, N.D. 1960. An analysis of bird populations in relation to forest succession in Algonquin Provincial Park, Ontario. Ecology 41:126-140.
• Martin, P.R. 1994. Effects of forest management practices and forest-cutting history on the songbird communities of mature hardwood forest stands, Lake Opinicon, Leeds/Frontenac Cos., Ontario. Ontario Ministry Natural Resources, Brockville, Ontario.
• Peck, G. and R. James. 1983. Breeding birds of Ontario: nidiology and distribution. Vol. 2-Passerines. Misc. Publ. Roy. Ont. Mus., Toronto.
• Rappole, J.H. and D.W. Warner. 1980. Ecological aspects of avian migrant behavior in Veracruz, Mexico. Pp. 353-393 in Migrant birds in the Neotropics (A. Keast and E.S. Morton, eds.). Smithson. Inst. Press, Washington, D.C.
• Rogers, C.M. 1985. Foraging success and tree species use in the Least Flycatcher. Auk 102:613-620.
• Sauer, J.R., J.E. Hines and J. Fallon. 2001. The North American Breeding Bird Survey, Results and Analysis 1966-2000. Version 2001.2, USGS Patuxent Wildlife Research Center, Laurel, MD.
• Sealy, S.G. and G.C. Biermann. 1983. Timing of breeding and migrations in a population of Least Flycatchers in Manitoba. J. Field Ornithol. 54:113-122.
• Sherry, T.W. 1979. Competitive interactions and adaptive strategies of American Redstarts and Least Flycatchers in a northern hardwoods forest. Auk 96:265-283.
• Sherry, T.W. and R.T. Holmes. 1988. Habitat selection by breeding American Redstarts in response to a dominant competitor, the Least Flycatcher. Auk 105:350-364.
• Southern, W.E. and L.K. Southern. 1980. A summary of the incidence of cowbird parasitism in northern Michigan from 1911-1978. Jack-Pine Warbler 58:77-84.
• Terrill, L.M. 1961. Cowbird hosts in southern Quebec. Can. Field-Nat. 75:2-11.
• Walkinshaw, L.H. 1961. The effect of parasitism by the Brown-headed Cowbird on Empidonax flycatchers in Michigan. Auk 78:266-268.
• Walkinshaw, L.H. 1966. Summer observations of the Least Flycatcher in Michigan. Jack-pine Warbler 44:150-168.
• Walkinshaw, L.H. and C.J. Henry. 1957. Yellow-bellied Flycatcher nesting in Michigan. Auk 74:293-304.
• Wisconsin Society for Ornithology. 2002. Wisconsin Breeding Bird Atlas.