Habitat

Adult White-throated Sparrow, white-striped morph, ON, Canada, May.

Adult White-thoated Sparrow, white-striped morph, ON, Canada, October.

Breeding Range

A habitat generalist or edge species, the White-throated Sparrow occurs in coniferous, deciduous and mixed forests, especially stands having numerous openings with low, dense, shrubby ground cover. It is abundant in second growth after logging, fires, insect damage and clearing, around edges of ponds, lakes, rivers, bogs and beaver meadows, in and around clumps of trees near tree line and where rock outcrops restrict forest growth, in clearings along roads and around cottages (Clark et al. 1983), and in brushy field edges and overgrown pastures. It avoids very dense spruce forest (Peters and Burleigh 1951, Salt and Salt 1976). In Algonquin Park, Ontario it is abundant in successional coniferous and mixed forest with openings carpeted with blueberries (Vaccinium spp.), but declines as forest closes (JBF). In Minnesota it prefers lowland conifers with black spruce (Picea mariana) (Lind and Hanowski 2004).

Some variation occurs across the range. In eastern and northern areas it is mainly in coniferous forests of spruce (Picea spp.), balsam fir (Abies balsamea), eastern hemlock (Tsuga canadensis), eastern white cedar (Thuja occidentalis), tamarack (Larix laricina), and pines (Pinus spp.), often mixed with deciduous trees including poplars (Populus spp.), white birch (Betula papyrifera) and alders (Alnus spp.) (Erskine 1977, Godfrey 1986, Rising 1996). Reported from blueberry barrens in Quebec (Spencer et al. 1996) and ptarmigan barrens in Newfoundland and Labrador (Judd 1951, Peters and Burleigh 1951).

In western Canada the White-throated Sparrow is the most abundant species in the boreal mixed-wood ecoregion, a broad band of forest lying between aspen parkland and northern coniferous forest (Schmiegelow et al. 1997). Trembling aspen (Populus tremuloides) is the dominant tree species with lesser components of balsam poplar (Populus balsamifera) and white spruce (Picea glauca). Black spruce occurs in lowlands. The greatest numbers occur in early successional and old aspen stands, the latter having more canopy gaps and understory than intermediate-aged aspen or conifer forest (Schieck et al. 1995, Kirk et al. 1996). Reproductive success is also greatest in young and old deciduous forest (Rangen et al. 2000). In British Columbia the preferred habitat is again trembling aspen with dense shrubby undergrowth (Campbell et al. 2001). In the Yukon Territory White-throats are most abundant in shrubby white spruce, mixed and balsam poplar forests, less common or absent in black spruce or lodgepole pine (Pinus contorta, Sinclair et al.2003).

In boreal mixed-wood the species is little affected by logging or forest fragmentation, remaining abundant in fragments and clearcuts (Schmiegelow and Hannon 1999). Populations showed no response to artificially created edges (Villard et al. 2007) and no apparent effect of retention of trees in cut blocks (Tittler et al. 2001). However, body condition, pairing success, site fidelity and reproductive success are reduced in clearcuts in comparison with edge and forest interior birds; numbers alone may not indicate suitable habitat (Hannah et al. 2008). It is gap-neutral compared with forest specialists (Hannon and Schmiegelow 2002). For similar results in Quebec see Rail et al. (1997). Displaced birds readily cross landscapes fragmented by agriculture or timber harvest (Gobeil and Villard 2002). In other parts of the range where White-throated Sparrows are less common, populations increase substantially in clearcuts (Freedman et al. 1981, Hanowski et al. 2003, Machtans and Latour 2003).

In Algonquin Park, Ontario WS males occupy open forest and forest edge, while TS males occur in both open and denser forest; however, nest sites of morphs do not differ (see Breeding) (Knapton and Falls 1982). In Maine, Brent Horton (pers. comm.) noted similar trends. In boreal mixed-wood in Alberta, Kevin Hannah (pers. comm.) compared abundance of morphs in interior, edge and clearcut. Both pair types occurred in all habitats but WS males peaked in edge while TS males were most abundant in interior forest. Open habitats may facilitate display of WS males. In Adirondack Park, New York, proportion of territories covered by trees did not differ between WS and TS males (Tuttle 1993) and a fine scale analysis of 12 vegetation types based on remote sensing found no differences in vegetation structure or proportion of open area. However WS males tended to cluster in continuous suitable habitat while TS males occurred in more isolated patches. This pattern, not unlike that in Algonquin Park, was interpreted by Formica et al. (2004) in terms of alternative breeding strategies (see Breeding for details). Despite these trends, individual territories sometimes change hands between birds of opposite morph in different years (e.g. Tuttle, 1993). Further analysis of remote sensing image texture found territories of TS males had significantly more spectral variance than those of WS males (Tuttle et al. 2006). These findings parallel those of Knapton and Falls (1982) but different methods make comparison difficult.

Spring And Fall Migration

Usually found in thick cover. In Kingston, Ontario, fall migrants are most abundant in poorly drained areas where dominant vegetation consists of dense shrubby growth (average height = 1.5 m) of willow (Salix spp.), dogwood (Cornus spp.), and buttonbush (Cephalanthus occidentalis) (JGK). In other areas similar shrubby habitat is used; species composition may vary. Also found in towns and urban areas where only patches of cover are available.

Winter Range

Habitat, like that frequented during migration, is characterized by thick cover. Individuals rarely venture far into open. Found in and along edges of woodlots, along hedgerows, in dense vegetation in ravines, and adjacent to watercourses, swamps and cattail marshes. Also found in weedy fields, town parks, even urban areas; frequents urban habitats more than most other sparrows. An experimental study in N. Carolina found White-throated Sparrows only in fields where weedy borders were unmowed (Marcus et al. 2000).