Olive-sided flycatcher (Contopus cooperi) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

The Olive-sided Flycatcher is most often associated with natural forest openings, forest edges near natural openings (such as wetlands) or open to semi-open forest stands and will use human-made openings (such as clearcuts) (Altman and Sallabanks 2000). The species will use early successional forest, although the presence of tall snags and residual live trees for foraging and nesting is essential. Open forest habitat used by Olive-sided Flycatchers is generally dominated by conifers or mixed forest, and is often near water or wetlands (ON: Cheskey 1987, BC: Campbell et al.1990, QC: Gauthier and Aubry 1996, YT: Sinclair et al. 2003). In boreal Canada it may be particularly associated with open habitat of muskeg, bogs and swamps dominated by spruce (Picea spp.) and tamarack (Larix laricina) (ON: Cheskey 1987, QC: Gauthier and Aubry 1996, MB: Manitoba Avian Research Committee 2003). In the boreal forest of western Canada (BC, AB, SK, YT, NT) the Olive-sided Flycatcher was generally associated with young forest (0-30 years) post-fire or young forest (0-10 years) and post- clearcut harvest that contained residual live trees. It was also found in old mixedwood forest (>125 years post-fire) (Schieck and Song 2006). In the Atlantic Provinces, the Olive-sided Flycatcher is found in open woodland and other forested areas where scattered trees remain after clearcutting or fire. They are less common in areas dominated by hardwoods, or where dense young second-growth forest has developed after fires or farm abandonment (Erskine 1992). In Alaska, perches used by males while singing were 1.4 times taller than the surrounding canopy and generally white spruce (P. glauca) containing a dead top, or completely dead white spruce trees (Wright 1997).

In Ontario, nests are most often placed in conifers, such as white spruce, black spruce, jack pine (Pinus banksiana) and balsam fir (Abies balsamea) (Peck and James 1987). In Alaska, Wright (1997) found that nests were placed in predominantly live (81% of nest trees) coniferous trees that were 0.9 times shorter than the surrounding canopy. Nest height averaged 6.4 m (range 3-12 m) above the ground. Robertson and Hutto (2007) found that successful nests were generally found under thicker canopy cover than unsuccessful nests.

Open areas with tall trees or snags for perching are required for foraging. The species generally forages from a high prominent perch where it sallies forth to intercept flying insects and then returns to the same perch. This habitat structure is used throughout the year.

While Olive-sided Flycatchers may use logged habitats in lieu of natural openings such as patches of burned forest, there is evidence that these areas may act as ecological sinks. Robertson and Hutto (2007) found that pairs nesting in selectively logged habitats in Montana had only half the breeding success compared with pairs nesting in natural openings.

Winter habitat is similar in structure but not in composition to that on the breeding grounds, being regularly observed along forest borders and in semi-open areas of the Andean foothills (BirdLife International 2005). However, this association with forest edges or clearings may be an artifact of the difficulties (and thus lack of observations) of studying birds in more intact forest stands in the Andes.

Habitat trends

In western forests, the Olive-sided Flycatcher can be found in both old growth forest (Carey et al. 1991; Schieck and Hobson 2000; Schieck and Song 2006) or in early to mid-successional forests derived from wildfire or timber harvest (Medin 1985; Medin and Booth 1989; Evans and Finch 1994; Hutto 1995; Steventon et al. 1998; Davis et al. 1999; Lance and Phinney 2001; Meehan and George 2003, Schieck and Song 2006). McGarigal and McComb (1995) found that Olive-sided Flycatchers were more abundant in a fragmented landscape of late-seral Douglas-fir (Pseudotsuga menziesii)-western hemlock (Tsuga heterophylla) forest with a high degree of edge habitat than unfragmented landscapes, suggesting that they may prefer edge habitat. Similar trends are expected in the eastern boreal forests of Canada, where the Olive-sided Flycatcher is associated with forested wetland, open forest, forest edge or early successional forest containing snags (e.g. Drapeau et al. 2000).

On the surface then, it would seem that although the amount of old-growth forest has obviously decreased over the past century or more, the amount of habitat attractive to Olive-sided Flycatchers could be remaining more or less constant since forest harvest continues to create openings favoured by the birds. Erskine (1992) suggests that the amount of suitable habitat may have actually increased since European settlement. The key question is whether this attractive habitat created by timber harvest is suitable for successful breeding or not. The continued decline of Olive-sided Flycatchers across their breeding range (BirdLife International 2004) despite their reputed positive association with timber harvest suggests that either breeding habitat supply may not be the only limiting factor for this species or that early successional forests created by timber harvest are unsuitable in some way for successful breeding and are acting as ecological sinks. Robertson and Hutto (2007), as mentioned above, present evidence that harvested landscapes harbour more nest predators and birds that nest there suffer significantly greater egg and nestling loss.

Altman (1997) suggested that habitat loss in the South American wintering grounds was a potential factor in population declines; Orejuela (1985) stated that 85% of Andean montane forests have been significantly altered. Diamond (1991) estimated that, if habitat loss continued at present rates, the Olive-sided Flycatcher would lose 39% of its winter habitat between 1980 and 2000.

Habitat protection/ownership

Because the Olive-sided Flycatcher is found in forested landscapes throughout Canada, the majority of its distribution lies on Crown lands subject to forest management. Habitat protection must be carried out largely through forest management planning guidelines separately administered in each province and territory, and on federal lands (including Aboriginal lands). In some southern areas (e.g. Vancouver Island and the Maritime Provinces), remaining habitat is also found on extensive private lands. Olive-sided Flycatchers breed in numerous provincial and national parks.

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