Golden-winged warbler (Vermivora chrysoptera) COSEWIC assessment and status report: chapter 5
Habitat
Habitat requirements
a) Breeding grounds
Golden-winged Warblers aggressively defend all purpose territories from neighbouring conspecifics. The average territory ranges in size from 1-2 hectares and is considered large relative to that of other warbler species. Golden-winged Warblers tend to nest in loose aggregations or “colonies” that typically contain up to ten pairs of breeding birds (Confer and Knapp 1981; R. Fraser, unpub. data). Generally, areas that are logged, burned, and intermittently farmed can readily support the species.
Territories tend to contain patches of herbs and low shrubs (used for nests which are placed on the ground) and scattered trees plus a forested edge used for song posts and foraging (Frech and Confer 1987). Examples of some preferred habitat areas include hydro/utility right-of-ways, field edges, recently logged areas and beaver marshes. On the Canadian Shield alder bogs are often used, especially when there are some tall tree species present including Black Ash (Fraxinus nigra; Mills 1987).
The Golden-winged Warbler is a habitat specialist given its reliance on areas of early successional scrub (10-30 years into succession); they will not persist in an area when the stage of succession has exceeded their requirements (Confer and Knapp 1981; Confer and Larkin 1998). Territories in the earliest stages of succession, with high herb cover, support larger clutches than areas with higher tree and shrub cover (Confer et al. 2003)
b) Migration
Very little is known about Golden-winged Warbler habitat use while on migration; they appear to use various open woodland habitats, pine-oak, and scrub, often in foothill regions (NatureServe 2004) likely due to their reliance on insectivorous food items such as Lepidopteran larvae.
c) Wintering grounds
Golden-winged Warblers have been observed in mixed species flocks of Neotropical passerines on the wintering grounds in Costa Rica (Buehler et al. 2003), in Panama (Moore 1980) and in Colombia (Johnson 1980). These flocks require areas of open woodland and can be found in evergreen and semi-deciduous forests (Stiles et al. 1991). Golden-winged Warblers are rarely found in mixed-species flocks with conspecifics or Blue-winged Warblers (with generally only one Golden-winged Warbler observed in such mixed-species flocks; Moore 1980; Tramer and Kemp 1980).
The species has been observed at high elevations (1,500-3,000 m) while on the wintering grounds in various types of open woodland habitats, pine-oak and scrub (Hilty et al. 1985; Raffaele et al. 1998; Ridgely and Gwynne, Jr. 1989; Stiles et al. 1991; Stotz et al. 1996). Exceptions to this were observed by Keast (1980) who defined Blue-winged and Golden-winged Warblers as lowland dwellers, but contrastingly, also found Golden-winged Warblers at 1,000-3,000 m in Venezuela, and also in the Chiriqui highland rainforest in Panama. Within the preferred habitat types, the species is found along edges, primarily in the canopy (Stiles et al. 1991).
Habitat trends
Of the 29 avian species that have showed significant population declines between 1980 and 2000 (Breeding Bird Survey data - Sauer et al. 2005), 90% of these use disturbance-generated ecosystems. Such ecosystems can be broadly defined as consisting of open fields, shrublands, mid-successional forests, open parkland and forest edges (Confer and Pascoe 2003).
Before the arrival of Europeans scrubby habitat was created when native North Americans employed slash-and-burn agriculture (Askins 2000). After European arrival scrubland habitat likely declined due to intensive grazing and farming. However, beginning in the 1840s upwards of tens of millions of acres of farmland was abandoned once again creating areas of suitable habitat. Much of this land has now passed through old-field-succession and has become reforested (Askins 1993, 2000; Confer and Pascoe 2003) leading to an overall decrease in the availability of this habitat type in eastern North America (Confer and Pascoe 2003; Dettmers 2003; Gill 2004). In addition, given extensive human development, restoration of historical habitat types is not possible in many areas. Active management of disturbance-generated habitats is crucial for the survival of numerous bird species in North America, including the Golden-winged Warbler (Askins 1993; Confer and Pascoe 2003).
Habitat protection/ownership
Given their reliance on early successional scrub this species is often found on land that is privately owned. General estimates on the proportion of breeding Golden-winged Warblers found on public vs. private lands throughout Canada are unavailable.
Areas of protection in Canada include some privately owned land, parks owned by Parks Canada as well as by the Ontario Ministry of Natural Resources and the National Capital Commission (Gatineau). Data from Parks Canada show that Golden-winged Warblers have been seen in five national parks in Ontario: Bruce Peninsula/Fathom Five, Georgian Bay Islands, Point Pelee, St. Lawrence Islands and Pukaskwa (but does not breed at Point Pelee or Pukaskwa) as well as in Riding Mountain National Park in Manitoba (P. Achuff, pers. comm.). At least one university in Ontario (i.e. Queen’s University; R.J. Robertson, pers. comm.) also protects and maintains large tracts of land used by this species.
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