Description
Length is 13 cm. Male is glossy black with bright orange patches on the sides, wings, and tail; belly and undertail coverts are white. Female is gray-olive above, white below with yellow patches. Immature resembles female. By first fall, young male's patches show some salmon; by first spring, breast has some black spotting; full adult male plumage is acquired by second late summer. Often fans tail and spreads wings when perched, making the colorful patches conspicuous.
VOCALIZATIONS: Variable song, a series of high, thin notes usually followed by a wheezy, downslurred note (NGS 1987).
NEST: a firm, compactly woven cup of plant down, bark fibers, small rootlets, grass stems; lined with fine grasses, weed stems, hair, sometimes feathers; decorated on outside with lichens, birch bark, bud scales, plant down; bound with spider silk; built entirely by the female, typically requiring 1 week or more (but sometimes less than this). Outside diameter 2.75 in (7 cm), height 3 in (7.6 cm); inside diameter 1.75 in (4.4 cm), depth 1.5 in (3.8 cm).
EGGS: Average size 16.2 x 12.3 mm. Oval to short-oval. Shell smooth, has slight gloss. White, grayish white, creamy white, greenish white; dotted, spotted, blotched with reddish-browns, grays; often concentrated at large end.
Habitat
BREEDING: Various mature and second-growth wooded habitats. Deciduous and mixed deciduous-coniferous second-growth forests, alder swamps, old growth forests with regenerating trees (e.g., around tree-fall gaps), willow thickets, small groves; low, damp, second-growth deciduous and mixed floodplain forests and river swamps; most abundant in mature deciduous forest stands, but also may occur in young woods less than 15 years old; requires closed canopy and prefers dense midstory and understory and well-developed undergrowth; use of pole-stage stands apparently varies geographically (Cruickshank 1979, Crawford et al. 1981, Harrison 1984, DeGraaf 1985, Bushman and Therres 1988, Sherry and Holmes 1997). Nests usually are placed in an upright fork of a deciduous understory sapling, shrub, or tree, occasionally in a vine tangle or old vireo nest; nest usually is about 1-6 m above ground, sometimes as high as 28 m.
Southeastern U.S.: Primary breeding habitats in the Piedmont and Coastal Plain are bottomland hardwoods and swamps, especially in extensive stands. In the mountains this species occurs in hardwoods along streams, usually where it is open and not heavily wooded. Birds are less frequent in medium-growth hardwood forests away from water. Hamel et al. (1982) described the key habitat requirements for breeding as hardwood forests near water. They provided the following details on habitat use and suitability in Virginia, North Carolina, South Carolina, Georgia, and Florida. The following five vegetation types used by this species in five physiographic provinces (Mountains, Sandhills, Piedmont, Inner Coastal Plain, and Outer Coastal Plain) are considered in order of suitability: elm-ash-cottonwood is suitable at the sapling-poletimber stage, optimal at the late-successional sawtimber stage; southern mixed mesic hardwoods and oak-gum-cypress are suitable at both the sapling-poletimber stage and sawtimber stage; oak-hickory and cove-hardwoods are marginal habitat at the sapling-poletimber stage and suitable at the sawtimber stage. In all cases, shrubs and midstory are used for all activities (feeding/foraging, nesting, perching, roosting, and singing), whereas the overstory is used for feeding/foraging, perching, roosting, and singing, but not nesting. No specific vegetation sizes were given. Yellow birch is significantly preferred for nesting, and fledging success is significantly higher in yellow birch than beech or sugar maple; this result is especially true for large, old trees. Nest concealment from predators accounts for these patterns (Crew and Sherry, unpubl. data).
Northeastern and north-central U.S.: In New York, breeders use low, damp woods and have been found in mixed woodland with a considerable growth of pine and hemlock; in the Adirondacks, nest sites often occur where spruces predominate. In Ohio, Michigan, and other sections of the Midwest, this species inhabits the maple, elm, ash, and pine-oak association of the larger, more mature swamp forests, although it is sometimes found among similar trees and brush in the larger upland woods. In the far Northwest, it shows a decided preference for willow trees and alder thickets. In Maine, the bird is found in hardwood or mixed deciduous and coniferous woodlands; these may be low, damp situations but birds are also often found in the second-growth of trees and brush of the dry sandy plains. Alder and willow thickets bordering streams and ponds are used here also (Bent 1953). In New Hampshire, redstarts are especially abundant in second-growth edge and in old-age northern hardwood forests, but they also occur in other moist woodlands, mixed hardwood-conifer woods, and alder and willow thickets. Here, this species breeds from near sea level to above 3000 ft (910 m), where the highest elevation hardwoods grade into conifers in the White Mountains (Sherry and Holmes 1994).
Quantitative habitat measures have been documented in a few studies. Sabo (1980) measured habitat selection in the White Mountains of New Hampshire and listed the following parameters: mean elevation - 830 m, canopy height - 10.4 m, canopy coverage - 74%, conifer foliage volume - 38%, conifer foliage cover (0-2 m) - 20%, broad leaf foliage volume (>5 m) - 92%, and dbh of live trees - 11 cm. Collins et al. (1982) quantified habitat in north-central Minnesota: ground cover - 67.7%, shrub cover - 70.7%, canopy cover - 66.3%, canopy height - 14.5 m, conifers - 4.7%, and numbers of species of trees per 0.04 ha circle - 4. In addition, Collins et al. (1982) surveyed vegetation and recorded the numbers of trees in different size classes: 10.7 (7.5-15 cm), 10.7 (15.1-23 cm), 8.2 (23.1-30 cm), 4.6 (30.1-38 cm), 1.1 (38.1-53 cm), 0.3 (53.1-68 cm), and 0.1 (>68.1 cm). Sherry and Holmes (1985, unpubl. data) documented significant preferences for deciduous stands of trees along a deciduous-coniferous gradient.
NON-BREEDING: In winter and migration, habitats include various kinds of forests, woodlands, scrublands, and thickets, including mangroves; uses a wide variety of agricultural habitats (e.g., cacao, citrus, pine plantations, mango, and sun and shade coffee plots) (Robbins et al. 1992). Primary wintering habitats are mainly in broadleaf evergreen woods and thickets, such as hammocks and mangroves (Hamel et al. 1982). In Venezuela, mangroves were a transitory habitat, used primarily in the middle of the wintering period by a low number of females (Lefebvre et al. 1992). In Jamaica, widespread in various habitats and are regularly found in drought-deciduous dry limestone forest, citrus, wet limestone forest (evergreen), gardens, and residential areas (Holmes et al. 1989, Holmes and Sherry 1992); they tend to be most abundant at lower elevations (Sherry, pers. comm.). Redstarts in Jamaica segregated by sex, with males in mangroves and females mainly in contiguous scrub habitat (Parrish and Sherry 1994). In the Dominican Republic, habitats include strand vegetation, mangroves, scrub, disturbed dry forest, riparian, urban, disturbed wet forest, mesic forest, and wet forest (Arendt 1992). In the Yucatan Peninsula, redstarts prefer moist forest, but also inhabit dry forest, wet forest, field and pasture, and acahual; late-successional forest stages are clearly preferred (Lynch 1992); redstarts were the third most common species found in mature semi-evergreen forest (after hooded [WILSONIA CITRINA] and magnolia warblers [DENDROICA MAGNOLIA]); were also found in mid-successional Acahual although less commonly so, and were rarely found in field/pasture habitat (Lynch 1989).
Ecology
BREEDING POPULATION DENSITY: Published information on bird densities from breeding bird censuses in the southeastern U.S. between 1947 and 1979 were summarized by Hamel et al. (1982). Mean (standard error) density was listed as 8.7 (2.8) pairs per 40 ha with a density range of 2.7-87 pairs per 40 ha. In northern New Hampshire (White Mountains), Sabo (1980) recorded average densities of 40 pairs per sq km in subalpine habitats, and 9 pairs per sq km in virgin spruce groves. Sherry and Holmes (1988) reported a range of 2.5-6.75 male territories on 10-ha sites at the Hubbard Brook Experimental Forest, New Hampshire. When population trends for the month of June (mid-breeding period) at Hubbard Brook were analyzed for the period 1969-1986, Holmes and Sherry (1988) found the mean (standard deviation) number of adult to be 28.67 (8.84) birds per 10 ha. In Maryland, Whitcomb et al. (1981) reported territorial densities to be 71 males per sq km.
Two studies of bottomland hardwood forests provide data from similar censusing techniques: Mitchell and Lancia (1990) found densities to be the highest in edge habitat (an average 0.14 birds per 25 m radius 10-min point count) in South Carolina. On the Roanoke River National Wildlife Refuge in North Carolina, R. Sallabanks (unpubl. data) found densities to be highest in the interior of wide levee forest patches (an average 0.57 birds per unlimited radius 10-min point count). Between 1986 and 1988, Sherry and Holmes (1989) found the number of yearling males to be low (0-1 males per 5 ha) compared with older males (6-8 males per 5 ha).
WINTERING POPULATIONS: Solitary in winter (Stiles and Skutch 1989). Defends winter territory (Jamaica, Holmes et al. 1989, Marra et al. 1993; Mexico, Rappole and Warner 1980); individuals commonly return to the same territory in successive years. Density in winter in Jamaica was 10-51 per 10 ha, comparable to breeding densities reported for eastern U.S., but greater than densities reported for other sites in the Caribbean and Mexico (0-17 per 10 ha) (Holmes et al. 1989; see also Bennett 1980). Winter densities were listed by Hamel et al. (1982) as a mean (standard error) of 2.5 (1.5) pairs per 40 ha with a density range of 1-4 pairs per 40 ha.
TERRITORY SIZE: Little information exists on territory size. Freemark and Merriam (1986) listed territory size as less than 2 ha near Ottawa, Canada. Based upon 14 birds, Sabo (1980) found territory size to be 0.6 ha.
COMPETITION: Several studies have addressed habitat selection and territory occupancy in response to both intra- and inter-specific competition (Ficken and Ficken 1967, Sherry 1979, Sherry and Holmes 1988, 1989, Secunda and Sherry 1991). In New Hampshire, Sherry and Holmes (1988) found the density of redstart territories to be slightly higher when a dominant competitor, the least flycatcher (EMPIDONAX MINIMUS), was absent (approximately 4.4 territories per 4 ha) than when present (approximately 4.0 territories per 4 ha). Least flycatchers locally excluded after second year redstarts from best patches of habitat within a heterogeneous array of such patches (Sherry and Holmes 1988).
MORTALITY FACTORS: Weather accounted for most nest losses during the building stage and caused starvation of nestlings in some years at Hubbard Brook (Sherry and Holmes 1994). Widespread starvation in 1984 was probably caused by a series of heavy rainstorms during the nestling period that depressed insect abundances, or reduced foraging time or success, or both (Sherry and Holmes 1992).