Habitat

Iliaca Group.

Prefers thick cover, especially brushy woodland edges, grown-up fields, cut-over woodland, and scrubby woods. In ne. Canada, prefers almost impenetrable stands of low shrubby black spruce (Picea mariana), balsam fir (Abies balsamea), tamarack (Larix laricina), aspen (Populus spp.), birch (Betula spp.), willow (Salix spp.), and alder (Alnus spp.) bordering wet boggy areas (Terrill 1968, Rising 1987). In Alaska and nw. Canada, alder and willow thickets in spruce forest, often among white spruce (Picea glauca; Austin 1968). In Newfoundland, highest densities in tuckamoor (clumps of wind-blown stunted conifers) and scrub forest; also common in successional old fields, cut-over and burned areas; less common in continuous coniferous forest, and both rocky alpine and coastal barrens (Blacquiere 1979). In Newfoundland, also nests in closed-climax balsam fir, black spruce, and white spruce forest, with some bare ground for foraging a prerequisite (Threlfall and Blacquiere 1982).

Unalaschcensis Group.

Found from beach to timberline in mostly deciduous thickets, preferring willow and blackberry (Rubus spp.) thickets, lush riparian vegetation, and streamside brush (Linsdale 1928a, Williamson and Peyton 1962, Austin 1968, Louisiana State University Museum of Natural Science [LSUMNS]).

Schistacea Group.

In the Great Basin, prefers to nest in impenetrable riparian thickets (usually near watercourses or mountain meadows) consisting of alder, water birch (Betula occidentalis), willows, currants and gooseberries (Ribes spp.), and rose (Rosa sp.; Salt 1957, Austin 1968, Zink 1986). P. i. altivagans breeds in both small dense clumps of stunted spruce and patches of tangles of alder and false hellebore (Veratrum spp.) growing above treeline (Austin 1968).

Megarhyncha Group.

Nests in montane chaparral consisting of brushy fields, occurring from 1,220 m to 3,000 m (Zink 1986). Likes burned-over forest land at a stage of recovery with heavy growth of brush (Austin 1968). At sites in Sierra Nevada, postfire, Fox Sparrow densities change as brushy fields of chaparral mature (Bock and Lynch 1970, Bock et al. 1978). Approximately 10 yr after a fire, montane chaparral reached a density sufficient to support the species (Bock and Lynch 1970). Most common plants in this montane chaparral include green-leaf manzanita (Arctostaphylos patula), mountain whitethorn (Ceanothus cordulatus), and bush chinquapin (Castanopsis sempervirens; Austin 1968, Zink 1986, Burns and Hackett 1993). In Green Mtns., south of main Sierra Nevada, Fox Sparrow found in elderberry (Sambucus sp.) thickets (Zink 1986). At one site in Hume, Fresno Co., CA, nesting habitat consists of roughly 35% mixed coniferous forest and 65% chaparral (Burns 1988, Burns and Hackett 1993). Relative plant abundance in the chaparral at Hume was approximately 60% mountain whitethorn, 20% green-leaf manzanita, 10% sierra gooseberry (Ribes roezlii), and 5% bush chinquapin (Burns 1988, Burns and Hackett 1993). Proportions of different tree species in this same area included 45% giant sequoia (Sequoiadendron giganteum), 40% white fir (Abies concolor), 10% ponderosa pine (Pinus ponderosa), and 5% sugar pine (Pinus lambertiana; Burns 1988).

During migration, Iliaca group Fox Sparrow often scratches in leaf litter in open hardwood forest, where little or no ground cover (Austin 1968). Also likes swampy tangles and weedy stream boarders (Austin 1968). In Colorado, found in lowland riparian shrublands (Andrews and Righter 1992). During migration (mainly during fall), unalaschcensis group regular in California’s eastern deserts (Garrett et al. 2000). For schistacea group, during spring migration, mostly from late Mar through late Apr, appears in small numbers in California’s desert oases (Garrett et al. 2000). During migration through Colorado, found in wooded riparian areas (Andrews and Righter 1992). Among megarhyncha group, during early spring, Thick-billed Fox Sparrow appears at oases in California deserts (Garrett et al. 2000).

Iliaca Group.

Prefers thick cover of thickets and underbrush, especially brushy tangles on edge of woods and dense willow or weedy areas along streams (Terrill 1968).

Unalaschcensis Group.

Prefers chaparral, ranging from arid to damp, spending much of its time in ground litter beneath screening cover of thick vegetation (Austin 1968). In s. California, predominates along with schistacea -group birds in relatively tall chaparral vegetation on cooler, more mesic north-facing slopes (Garrett et al. 2000). Common plant cover includes: thimbleberry (Rubus parviflorus), poison-oak (Toxicodendron diversiloba), nine-bark (Physocarpus sp.), Ceanothus spp., coyote bush (Baccharis pilularis), and salal (Gualtheria shallon; Grinnell and Miller 1944, Austin 1968).

Schistacea Group.

In s. California, predominates along with unalaschcensis -group birds in relatively tall chaparral vegetation on cooler, more mesic north-facing slopes (Garrett et al. 2000).

Megarhyncha Group.

Core wintering range consists of chaparral, with birds of this group predominating on warmer south-facing slopes dominated by chamise (Adenostoma fasciculatum) in s. California (Garrett et al. 2000).