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Scissor-tailed Flycatcher
Tyrannus forficatus
NatureServe conservation status
Global (G-rank): G5
State (S-rank): SNA
External links
Species range
BREEDING: eastern New Mexico, southeastern Colorado, southern Nebraska, central Missouri, central Arkansas, and western Louisiana south to northern Nuevo Leon and southern Texas (AOU 1998). NON-BREEDING: central and southern Florida, and in Middle America from southern Veracruz and Oaxaca south to central Costa Rica (rarely to western Panama); casual north to California and southern Louisiana (AOU 1998).
Migration
Migrates between breeding grounds in south-central United States and northeastern Mexico and wintering grounds in southern Mexico, Central America, and extreme southern Florida. Typically departs winter habitat in March and April and arrives on breeding grounds from mid-March through early May (Regosin 1998). Spring migrants have been observed in Texas as early as February (Oberholser 1974). Males generally arrive on the breeding grounds before females (Regosin and Pruett-Jones 1995). In late summer, forms large premigratory communal roosts composed of up to 1,000 individuals (Fitch 1950, Regosin 1998). May use the same roost sites from year to year (Baumgartner and Baumgartner 1992, Regosin 1998). Migrates south between late August and mid-October (though sometimes lingers into winter; Baumgartner and Baumgartner 1992, James and Neal 1986, Oberholser 1974, Regosin 1998). Arrives on wintering ground from September-November (Regosin 1998, Stiles and Skutch 1989). Migrates at night (Bent 1942).
Habitat
BREEDING: Inhabits open country (savannas, grasslands, croplands, pastures, gardens, parks, golf courses, and urban areas) with scattered trees and shrubs for perching and nesting. Natural plant associations inhabited during the breeding season include mesquite-acacia (Prosopis-Acacia) savanna, bluestem-grama (Andropogon-Bouteloua) prairie, blackland prairie, and bluestem-sacachuista (Andropogon-Spartina) prairie (Regosin 1998). Nests principally in isolated trees or shrubs, but also in tree or shrub copses or, more rarely, in riparian forests (Fitch 1950, Nolte and Fulbright 1996, Regosin 1998). Man-made structures, including telephone poles, streetlights, television antennas, power transformers, and windmills are sometimes utilized for nesting (Bent 1942, Fitch 1950, James and Neal 1986, Regosin 1998).In eastern Texas, 91 percent of nests were constructed in honey mesquite (Prosopis glandulosa), and most (58 percent) were on branches oriented to the northwest, north, and northeast, away from the prevailing winds (Nolte and Fulbright 1996). Other trees used for nesting include hackberry (Celtis leavigata), honey locust (Gleditsia triacanthos), huisache (Acacia smallii), lime pricklyash (Zanthoxylum fagara), American elm (Ulmus americana), cedar elm (U. crassifolia), water oak (Quercus nigra), live oak (Q. virginiana), post oak (Q. stellata), retana (Parkinsonia aculeata), pecan (Carya illinoensis), cottonwood (Populus deltoides), and yaupon (Ilex vomitoria; Bent 1942, Fitch 1950, Nolte and Fulbright 1996, Regosin and Pruett-Jones 1995). Nests vary from 2.1-24 meters above the ground (Fitch 1950, James and Neal 1986, Nolte and Fulbright 1996, Regosin and Pruett-Jones 1995).NON-BREEDING: inhabits savannas, pastures, croplands, second-growth scrub, forest edges, and developed areas, from lowlands to 2300 meters (Regosin 1998, Stiles and Skutch 1989).
Food habits
Hunts from a perch; darts out and captures insects as they fly by. Also gleans insects off vegetation or captures insect prey on the ground. Rarely hops from branch to branch or hovers near trees to forage on invertebrates and berries (Fitch 1950, Regosin 1998). Will forage on insects at night under artificial light (Allan 1950, Frey 1993). Contents of 129 stomachs collected in Texas and Florida included 96 percent animal matter and 4 percent plant matter. Principal invertebrate prey included grasshoppers and crickets (Orthoptera), beetles (Coleoptera), bees and wasps (Hymenoptera), bugs (Hemiptera), caterpillars and moths (Lepidoptera), flies (Diptera), and spiders (Arachnida; Beal 1912). Fall flocks have been observed in cotton fields feeding on cotton worms (Aletia argillacea; Bent 1942). Grasshoppers were found in the stomachs of 4 out of 5 birds examined in Texas (Fitch 1950). Eats fruits of red mulberry (Morus rubra), hackberry, pigeonberry (Rivinia humulis), and dewberry (Rubus spp.). On the winter range feeds on insects and fruit; large numbers sometimes gather in trees to feed on fruit (Regosin 1998, Stiles and Skutch 1989). Water is obtained from puddles and cattle watering tanks (Fitch 1950, Regosin 1998).
Ecology
In Texas, density of breeding pairs varied from 1.6-3.3 pairs per 10 hectares and defended territories were estimated to encompass 0.2-0.4 hectare (Fitch 1950). In two study areas in Oklahoma, breeding densities were 0.5 and 0.7-1.1 pairs per hectare, respectively (Regosin 1998). In another Oklahoma study, the breeding density was 0.5 pairs per hectare (Baumgartner and Baumgartner 1992). In Texas, an average of 52.7-112.6 individuals have been sighted on some Breeding Bird Survey routes (Price et al. 1995). Nests are built 16-308 meters apart from each other (Fitch 1950, Regosin and Pruett-Jones 1995).Inter-year site fidelity was observed in Texas by Nolte and Fulbright (1996). In one year, six nests were placed in shrubs used for nesting the prior year. In the third year of study, 25 nests were found in shrubs containing nests in at least one of the two previous years. Eight shrubs were used for nesting in subsequent years even after they died. Regosin and Pruett-Jones (1995) also observed site fidelity in Oklahoma: 47.8 percent of males and 57.6 percent of females breeding on the study area returned the second year, and 42.5 percent of all banded birds (breeding and non-breeding combined) returned to the study area the second year. Returning males held territories in the same general locations between years. Six (40 percent) of 15 returning females nested in the same tree both years, five (33.3 percent) nested within 100 meters of their first-year nest, and the remaining four (26.7 percent) nested greater than 100 meters away from their first-year nest.Because males arrive on the breeding grounds ahead of females, the sex ratio is male-biased early in the breeding season, but approaches parity as more females arrive (Regosin and Pruett-Jones 1995). Thought to attain sexual maturity in one year (Regosin 1998). Nestlings have been found infested with mites (Liponyssus bursa; Fitch 1950). In winter, can be locally abundant; hundreds converge to roost together in trees in marshes, mangroves and towns (Stiles and Skutch 1989).
Reproductive characteristics
Nesting extends from late March through late August (Oberholser 1974). Females alone build the nest, incubate eggs and brood young; both sexes feed nestlings (Fitch 1950). One egg is laid per day until the clutch is complete (Fitch 1950). Clutch size is usually four to five, but ranges from three to six (Regosin 1998). In a two-year study in Oklahoma, mean clutch size was 4.7 eggs the first year and 4.5 eggs the second. Clutch sizes of second nesting attempts were smaller than first attempts (average of 4.0 eggs the first year and 4.4 eggs the second). Females that initiated clutches later in the season tended to lay smaller clutches than earlier-nesting females. One female made four nesting attempts. Two females laid three clutches of eggs for a total of 14 eggs apiece (Regosin and Pruett-Jones 1995). In Texas, clutch size ranged from 3-5 eggs (mean = 3.8) in 16 nests (Fitch 1950). At another Texas site, clutch size averaged 4.4 eggs in one year and 4.5 eggs in another (Nolte and Fulbright 1996). Average clutch size of 16 nests in Kansas was 4.7 eggs (Murphy 1988). Average incubation time was 14 days in Texas (Fitch 1950) and 14.7-14.9 days (range = 13-22), depending on year, in Oklahoma. Eggs in earlier nests took longer to hatch than eggs in later nests, possibly as a result of colder weather earlier in the breeding season (Regosin and Pruett-Jones 1995). The nestling period averages 15.3-15.4 days (range = 14-17; (Regosin and Pruett-Jones 1995). Hatching success in Texas was 80 percent (Fitch 1950), and ranged from 85.7-88.9 percent in Oklahoma (Regosin and Pruett-Jones 1995). In Oklahoma, nesting success ( percent nests that fledged at least one young) varied from 18.6-43.1 percent and, depending on year, successful pairs produced an average of 2.8-3.7 fledglings (Regosin and Pruett-Jones 1995). In Texas, combined nesting success for two years of study was 39 percent and the mean number of young fledged from successful nests per year ranged from 3.0-3.2. Depending upon year, 15.4-36.4 percent of nest failures was due to predation and 7.7-45.5 percent was a result of inclement weather. Successful nests had less horizontal cover but more vertical cover than unsuccessful nests (Nolte and Fulbright 1996). In Oklahoma, 34 percent of nests were dislodged by storms during one summer (Regosin and Pruett-Jones 1995). Of three instances in which females initiated egg laying after fledging young from earlier nests, the second nesting attempt failed in two cases, but was successful in the third (Regosin and Pruett-Jones 1995).
Threats or limiting factors
Threats are minimal; readily adapts to open habitats created by humans. HABITAT: Brush eradication in portions of the breeding range could reduce nesting habitat (Nolte and Fulbright 1996). PREDATION: Suspected predators of eggs/nestlings include kingsnakes (LAMPROPELTIS spp.), racers (COLUBER CONSTRICTOR), coachwhips (MASTICOPHIS FLAGELLUM), and great-tailed grackles (CASSIDIX MEXICANUS; Nolte and Fulbright 1996). Confirmed predators of nestlings include Cooper's hawks (ACCIPITER COOPERI) and American crows (CORVUS BRACHYRHYNCHOS; Regosin and Pruett-Jones 1995, Regosin 1998). PARASITISM: Nests are occasionally parasitized by brown-headed cowbirds (MOLOTHRUS ATER), but cowbird eggs are typically ejected (Friedman 1963, Regosin 1994, Regosin 1998). INCLEMENT WEATHER: Severe windstorms and thunderstorms can reduce reproductive success by dislodging nests and reducing prey availability (Regosin and Pruett-Jones 1995).
