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COSEWIC Assessment and Status Report on the Bicknell's Thrush Catharus bicknelli in Canada (1999)

Habitat

 

Habitat requirements

Typical/traditional habitat

In the United States, where most Bicknell's Thrush research has been conducted until the 1990s, the species is a strict habitat specialist.  Described as a "mist-and-height-Ioving" bird (Gillet 1935) of the "tree-line" ecotone (Petersen 1990), Bicknell's Thrush populations are confined mainly to altitudes of 914 m to the tree line on rocky peaks (Fig. 7), with some scattered pairs breeding down to 762 m (Wallace 1939, Rimmer et al. 1993). Atwood et al.(1994) detected Bicknell's Thrush on 79% of all high-elevation peaks (≥914 m) surveyed in New England and New York, on only 11 % of all mid-elevation peaks (762-914 m), and at no low-elevation (762 m) areas in northern Maine.

The species also occurs predominantly in traditional subalpine habitat in Quebec (Ouellet 1995, Rompré et al. 1997), in remnant patches of subalpine habitat in New Brunswick, and in structurally similar habitat in Cape Breton (Holmes and Nixon 1997, Nixon 1996).  In Quebec, a 1997 distribution survey located no birds at elevations below 620 m, even though censuses began at 315 m (Rompré et al. 1997).  The species' preference for high elevations was also demonstrated during the CWS/CFS surveys in New Brunswick and Cape Breton (Figure 5).  The species is only occasionally found at elevations as low as 200 m in Quebec (Ouellet 1995), and 300 m in New Brunswick and Cape Breton (Erskine 1992).

The subalpine forests favoured by Bicknell's Thrush are characterized by a wet, cool, windy climate that increases in severity with elevation (Reiners and Lang 1979, Sabo and Holmes 1983).   In Quebec, Rompré et al. (1997) found mistnetting of the species to be difficult due to frequent cold weather, strong winds and the presence of snow in late-June.  On Mt. Mansfield, Vermont, average monthly temperatures in the summer barely exceeded 10°C (Wallace 1939).  Sabo and Holmes (1983) found the average June temperature at 600 m versus 1000 m in New Hampshire to drop from 16°C to 12°C, the annual precipitation to increase from 130 mm to 150 mm, and the mean above-canopy wind speed to increase from 12 km/hr to 30 km/h.

Under these climatic conditions, the habitat is very dense and twig-rich, dominated by small, stunted, even-aged balsam fir and, to a lesser degree, spruce (Wallace 1939, Palmer 1949, Able and Noon 1976, Sabo 1980), often underlain by a dense flush of young (mainly fir) growth (McFarland pers. comm.).  According to Wallace (1939), these conifer stands become increasingly dense and stunted as altitude progresses, until "at the tree limit they are so closely matted together that they are often virtually impenetrable.  Indeed, their branches may be so closely interlaced that it is sometimes possible to walk over the tops of them without sinking through."

Mortality is high in these stands, with many of the conifers dead or dying (Wallace 1939). There is often an additional number of taller snags scattered throughout (C. Rimmer pers. comm.).

Bicknell's Thrush habitat in three areas in Quebec had a balsam fir composition (as measured by numbers of tree stems) of 88.5%, 75.1 % and 71.1 % (Rompré et al. 1997). White birch (Betula papyrifera) was also a regular component, interspersed with smaller numbers of mountain ash (Sorbus sp.), pin cherry (Prunus pensylvanica), mountain maple (Acer spicatum), and other hardwood species. Extensive mats of Sphagnum, Pleurozium schreberi, Cladina sp., Polytrichum sp. and other mosses and lichens are found beneath the trees (Wallace 1939, Dilger 1956, Sabo 1980, Nixon 1996, Rompré et al. 1997).

Average canopy height of Bicknell's Thrush breeding habitat tends to range from 3-7 m in New Brunswick (Nixon 1996) and Cape Breton (D. Busby unpubl. data), with mean heights in Quebec of 5.4 m (Parc de la Gaspésie), 7.5 m (ZEC des Martres) and 14.1 m (Mont-Mégantic; Rompré et al. 1997). Sabo (1980) calculated a mean canopy height of 4.8 m in Bicknell's Thrush habitat in New Hampshire.  Stands also tend to be dominated by small-diameter trees.  In Quebec, small diameter size trees (.5 cm; measured 20 cm above ground level) make up 89.3%, 85.3%, 55.9% of stems on the previously mentioned sites. In New Hampshire, mean diameter at breast height (dbh) was 7 cm (Sabo 1980).

Figure 5.  Occurrence of Bicknell’s Thrush in New Brunswickand Cape Breton, N.S., by elevation (m), based on surveys conducted from 1995-1998 by the Canadian Wildlife Service and the Canadian Forest Service.  (Courtesy of D. Busby, CWS – Atlantic Region.)

Figure 5.  Occurrence of Bicknell’s Thrush in New Brunswickand Cape Breton, N.S., by elevation (m), based on surveys conducted from 1995-1998 by the Canadian Wildlife Service and the Canadian Forest Service.  (Courtesy of D. Busby, CWS – Atlantic Region.)

As stand characteristics within the subalpine zone are in part determined by cold and often severe weather patterns, similar habitat (extremely dense stands of stunted, windswept fir and spruce) also occurs at some coastal and island locations.  Historically, the species was known to breed in such coastal habitat at a number of locations in Canada (see Distribution section), but it is now limited to Cape Breton lowlands and peripheral small islands.

Non-typical/non-traditional habitat

Recent observations in southern Quebec (Ouellet 1993, 1995), northern New Brunswick (Erskine 1992, Nixon 1996, Holmes and Nixon 1997) and Cape Breton (D. Busby peTS. comm.) indicate that in Canada, Bicknell's Thrush also frequents second-growth or regeneration forests that follow large, stand-level disturbances such as clearcutting or fire.  This habitat is referred to as "non-typical" or "non-traditional" for two reasons.  First, the species is virtually absent from this habitat in the U.S., where the vast majority of research on Bicknell's Thrush has been conducted until the 1990s. Secondly, the species' presence in this habitat has only been recently detected.  In fact, it is possible that the species has been present in such habitat for years, but was overlooked (Ouellet 1993).

Bicknell's Thrushes are most commonly found in regeneration forests in New Brunswick.  Findings from a 1995 distribution survey in the northcentral and northwestern parts of the province showed that 91 % of all detected birds were located in regeneration, and only 9% in "typical" habitat (Nixon 1996).  More than 84% of all birds located during the survey were found on sites estimated to have been clearcut within the last five to 20 years (Nixon 1996).  On Cape Breton, Nova Scotia, the species is still found primarily in "typical" habitat, but approximately 25% of the population is estimated to occur in regeneration (D. Busby unpubl. data).  In Quebec, Ouellet (1993, 1995) suggested that a major shift in habitat preference has occurred (Table 2). However, Rompré et al. (1997) and Seutin (1998) contended, based on intensive surveys in 1997 and 1998, that alternative habitat is used in smaller proportion in Quebec than elsewhere in eastern Canada.

As in "traditional" habitat, the species is generally present in alternative stands at high elevations.  In New Brunswick and Cape Breton, most birds detected during the atlas period were found above 300 m (Erskine 1992).  No birds detected during distribution and habitat surveys in 1995-1997 were found below 426 m (Nixon 1996, Holmes and Nixon 1997, unpubl. data) and the species was found to increase steadily in density with elevations (Holmes and Nixon unpubl. data).

There appears to be some variability in the tree species composition of regeneration forests in which Bicknell's Thrush is found.  In Quebec and Cape Breton, Bicknell's Thrush has been located in regeneration dominated by balsam fir, with some spruce.  Hardwood species are also present (Prunus sp., Betula sp., Amelanchier sp., Acer spicatum, Populus sp., Sorbus sp.), but in small quantities (Ouellet 1993, Rompré et al. 1997, D. Busby pers. comm.).  In New Brunswick, stem counts on Bicknell's Thrush territories indicate that white birch is the dominant species. In 1996 and 1997, white birch comprised 48 and 44% of all stems, followed by balsam fir (30 and 25%) and pin cherry (15 and 22%; Holmes and Nixon 1997, unpubl. data).

Generally, Bicknell's Thrush tends to be located in regeneration of low average canopy heights. In Quebec, Ouellet (1995) found that occupied stands were generally less than 10 m in height, results consistent with stand heights measured in Cape Breton (3-7 m; D. Busby pers. comm.) and New Brunswick (2.1-5.9 m; Holmes and Nixon 1997).  Of 38 sites sampled by Holmes and Nixon (1997), average mean canopy height for 34 sites (89%) was 4.3 m or less.  As well, used regenaration stands are generally dense (Erskine 1992) and closely spaced, with average dbhs ranging from 4-15 cm (Ouellet 1993).  Small-stemmed trees (diameter of less than 2.5 cm) made up 74% of all stems on Bicknell's Thrush territories in New Brunswick (Holmes and Nixon unpubl. data).

A high degree of vertical ground cover has also been noted in regenerating stands. In northern New Brunswick, this cover was provided by closely spaced, low-branching conifers, mat-like, shrubby growths of mountain maple, dogwood (Comus sp.), pin cherry and elderberry, and ground plants such as raspberry (Rubus sp.), bracken and wood fern (Pteridium acquilinum, Dryopteris sp.), sarsaparilla (Aralia nudicaulis), and high grasses (Nixon 1996). Other common plant species, many of which have been previously noted under "typical" habitat, include Canada mayflower, boreal lily, bunchberry, Lycopodium sp., blueberry and snowberry (Nixon 1996, D. Busby pers. comm.).

Recent research in Quebec clearly indicated that not all coniferous or mixed regeneration forests in altitude are suitable for Bicknell's Thrush (Rompré et al. 1997, Seutin 1998).  The precise characteristics of occupied stands are still being researched, but necessary factors likely include a very high tree density within a few meters from the ground (Seutin and Connolly, unpubl. data).  Stand height (Holmes and Nixon 1997, Seutin 1998) and tree species composition (Seutin 1998) may also be important factors.

Observations of Bicknell's Thrush in regenerating forests in Quebec and the Maritimes raises the possibility that the species is less likely to be limited by habitat in Canada than in the United States. Currently, mixed second-growth forests are abundant in Quebec and in northern New Brunswick (ENixon peTs. obs.).  For a number of reasons, however, caution must be exercised in assuming that abundant second-growth habitat can replace traditional breeding habitat.  Firstly, while there is no doubt that Bicknell's Thrush occurs in regeneration habitats during the breeding season, there is as yet no proof that they successfully breed there; this habitat may actually represent a sink for Bicknell's Thrush. Secondly, there is no indication of a "shift" to second-growth habitat in the U.S. Northeast.  It is possible that extensive logging in eastern Canada, coupled with outbreaks of spruce budworm, may have seriously reduced the extent of "typical" habitat available to the species in Canada, forcing it to use lower quality habitat.  Thirdly, the species appears to select for specific age and structural characteristics within this habitat (Holmes and Nixon 1997, Seutin 1998), so only a portion of available regeneration is likely suitable at any given time.  Also, because of the transitional nature of these forests, the quantity of suitable habitat will vary over space and time, depending on harvest schedules and silvicultural practices.

Habitat distribution

Canada

In southern Quebec, large area of apparently high-quality habitat is found along the Gaspé Peninsula.  High-elevation peaks occur throughout much of the peninsular area; they are especially concentrated in the northeast, diminishing to smaller, more isolated areas west of Rimouski.  Suitable habitat is also found along the north shore of the St. Lawrence River.  A band of high-elevation areas extends along the shore from Quebec City in the west to Godbout in the east, with scattered areas occurring in the interior.  Extensive surveys in 1997 and 1998 revealed however that only a fraction of this habitat is currently used (Rompré et al. 1997, pers. comm.).  Small patches of habitat are also found in extreme southern Quebec in the Estrie region.  They are found on the few summits that reach more than 900m (i.e., Mont Mégantic, Mont Gosford and Montagne de Marbre).

In the Maritime provinces, the largest, most continuous highlands are found in the northcentral and northwestern regions of New Brunswick, where elevations range mainly from 200-500 m (Figure 6).  This is where the majority of Bicknell's Thrush detections have been reported.  A much smaller highland area (mainly 200-500 m) occurs in the southeast comer of the province (Albert County Highlands), although there is no evidence of a breeding population (A.I. Erskine pers. comm.).

High-elevation sites are limited on the Nova Scotian mainland. Few peaks above 300 m are found in the north (A.I. Erskine pers. comm.) and a small highland area is found in the southwest.  However, there is no breeding evidence of Bicknell's Thrush in either of these areas.  Bicknell's Thrush is found on Cape Breton Island, however, where a large block of suitable, high-elevation habitat extends along the northern peninsula.

In Prince Edward Island, some suitable habitat is found along the northern tip, in the form of wind-exposed, stunted conifer forests. Much of the island, however, is of a relatively low elevation, with habitat unsuitable to Bicknell's Thrush.

As in Quebec, there are a number of areas in the Maritimes containing apparently suitable habitat which are currently uninhabited by Bicknell's Thrush (e.g., Albert County Highlands in N.B, southwest N.S., P.E.I.).  It is possible that habitat size (A.I. Erskine pers. comm.) or degree of isolation from larger areas of suitable habitat (McFarland pers. comm.), not elevation, are the limiting factors.  Habitat patches may simply be too isolated or too small to support other than sporadic breeding. Although there is no data on the impact of habitat fragmentation or isolation on the species, Atwood et al. (1994) found that Bicknell's Thrush occurred less frequently on high-elevation (≥ 914 m) New England and New York mountain masses with < 5 km2 of estimated land area than they did on larger mountains with similar habitat.  Despite these findings, however, the species was still detected on 83% (n=76) of the surveyed mountains with < 5 km2 of land area at ³914 m elevation.

 

Figure 6.  Elevation contour map of the Maritime provinces(from Erskine 1992).

Figure 6.  Elevation contour map of the Maritime provinces(from Erskine 1992).

Figure 7.  Approximate distribution of Bicknell’s Thrush habitat in the United States(from Atwood et al. 1994).

Figure 7.  Approximate distribution of Bicknell’s Thrush habitat in the United States(from Atwood et al. 1994).

 

Northeastern United States

In Maine, suitable habitat occurs on a number of scattered, isolated mountain peaks, found mainly in the southwest part of the state close to the New Hampshire border (Allen 1898, Wallace 1939) and continuing northward toward Baxter State Park (Atwood et al. 1994).  There are also some coastal areas where harsh weather conditions have produced forests of a structure similar to that found at high elevations (Atwood et al. 1994).  Scattered peaks are also present in northern New Hampshire, with most suitable habitat concentrated in the White Mountains in the centre of the state (Faxon and Allen 1888, Wallace 1939, Atwood et al. 1994).  In Vermont, breeding habitat is restricted to the Green Mountains (Davenport 1903, Wallace 1939), a narrow band of peaks running down the centre of the state from Canada to Massachusetts, and to the Taconic Mountains in the southwest (Atwood et al. 1994).  In New York, good breeding habitat is found in the Adirondack Mountains in the north and the Catskill Mountains in the south (Wallace 1939, Palmer 1949, Peterson 1988, Marshall and Clapp unpublished ms).  Suitable habitat appears to be extremely isolated, and is relegated to a single peak in the northwest corner of the Massachusetts (Wallace 1939, Atwood et al. 1994).

Trend in Quantity and Quality of Habitat

Breeding Grounds

In Canada, Bicknell's Thrush habitat has been substantially altered in Quebec and the Maritimes over the last century by major infestations of spruce budworm (Choristoneura fumiferana).  Infestations have also occurred in the eastern U.S., mostly in Maine, although to a lesser degree (Hardy et al. 1986).  Spruce budworm outbreaks occur cyclically in spruce-fir forests, where budworm feed voraciously on balsam fir and white, red, and black spruce (Kettela 1983).  Damage to traditional breeding habitat was especially severe during the last infestation.  During its peak year (1975), the outbreak covered between 57 million ha (Kettela 1983) and 72 million ha (Hardy et al. 1986) of forested land in eastern Canada and the U.S. (Figure 8).  By the following year, significant volumes of dead and dying trees covered 3 million ha of land (Kettela 1983). Outbreaks and spruce-fir mortality were especially severe on Cape Breton Island, an area of prime breeding habitat for Bicknell's Thrush, and in Quebec, including the Gaspé Peninsula, where, by 1981, 10.2 million ha of land contained significant volumes of dead and dying trees.

Budworm populations were at their peak in 1975, and have since declined. However, budworm is still considered to be the most devastating forest insect pest in North America whether measured by tree mortality, hectares infested, or frequency and duration of outbreaks (Hardy et al. 1986).  It has also been noted that budworm infestations have increased in frequency, duration and severity since the start of the

Figure 8.  Areas of defoliation by the spruce budworm in eastern North America, 1975 (from Hardy et al. 1986).

Figure 8.  Areas of defoliation by the spruce budworm in eastern North America, 1975 (from Hardy et al. 1986).

20th century (Bailey 1924, Blais 1983, Hardy et al. 1986), with the last infestation also the most wide-spread (Kettela 1983).  Nevertheless, Erskine (1992) concluded that Bicknell's Thrush populations in the Maritimes have not been obviously affected by spruce budworm damage to forests.  In Quebec, however, R. Ouellet (pers. comm.) links the presence of Bicknell's Thrush in young, second-growth forests to previous budworm damage: the destruction of large expanses of spruce-fir habitat during the latest budworm infestation may have forced the species into young, regenerating forests.  While the impacts of logging on Bicknell's Thrush are unknown at this time, large-scale forestry operations are occurring throughout important breeding areas, including the Gaspé Peninsula and in areas north of the St. Lawrence, throughout the northcentral and northwestern highlands of New Brunswick, and in Cape Breton. In New Brunswick, the distribution of high elevation habitat is virtually contained within timber license land.  Clear cutting is in evidence throughout, with some peaks virtually denuded (E. Nixon pers. obs.).

The presence of Bicknell's Thrush in regeneration stands may be an indication of a greater adaptability or wider habitat niche than previously believed, or of a switching of habitat (Ouellet 1993).  However, based on current information, it appears that Bicknell's Thrush may be selecting for very specific habitat features within managed forest.  In Quebec, a 1997 survey indicated that birds had vacated sites which had been recently thinned during logging operations (Rompre et al. 1997, Seutin 1998).  As thinning operations are a common forestry practice throughout eastern Canada, such operations undoutably reduce the supply of suitable habitat for the species.

Another potential threat to Bicknell's Thrush is the fact that the distribution of suitable regenerating habitat will certainly vary over space and time.  In New Brunswick, where the species is found almost exclusively in regeneration stands, B. Donovan, a forestry management planner with a pulp and paper company operating in the highlands, predicts that the uneven age distribution of industrial forests will lead to a "crash" in young dense regeneration within the next few decades.  This has already happened in parts of Quebec (e.g., sectors of Parc des Laurentides).  Thus, while young regeneration is currently plentiful, its transitional nature may lead to the need for specific forest management practices in the future if there is to be sufficient habitat for Bicknell's Thrush, particularly in New Brunswick.

In the United States, where habitat is restricted to higher elevations, logging has not contributed significantly to habitat degradation.  Due to lack of accessibility, it is unlikely that forestry operations will ever prove feasible in these areas.  However, these high elevation habitats face different threats.  In New England (except, perhaps, in Maine) and New York, a steady decline in habitat quality may have been occurring over the last 30-40 years (Marshall in Erskine unpublished ms).  Research suggests that forest decline is due largely to the direct and indirect effects of atmospheric deposition (Vogelmann 1982, Rimmer and McFarland 1994).  While the effects of atmospheric deposition, particularly in the form of acid precipitation, are most evident in Bicknell's Thrush habitat in the northeastern U.S., its impacts may potentially be felt throughout the entire breeding range of Bicknell's Thrush (Vogelmann 1982).

High-elevation forests (>800 m) are particularly vulnerable to the effects of atmospheric deposition due to the high levels of acidity transmitted through cloud moisture, the major source of precipitation within these areas (Vogelmann et al. 1968). These forests also receive higher levels of rain and fog than low-lying areas. In Vermont's Green Mountains, forests at 1067-1372m receive twice the annual precipitation of a low-elevation (122m) forest only 50 km away, more than doubling the acid load (Vogelmann 1982).  Rain in the northeastern states is now calculated to be at least 30-40 times more acidic than that of pre-industrial times (Vogelmann 1982). Montane areas also receive more frequent exposure to other air pollutants, including lead, zinc, copper, vanadium and cadmium, all heavy metals known to be toxic to plants.

Severe declines in red spruce, an integral component of the species' breeding habitat in the Northeastern North America., have been documented since the 1960s, with dead and crown-damaged trees common in the Green Mountains of Vermont, the White Mountains of New Hampshire, New York's Adirondack Mountains, Quebec's Laurentians, and the Appalachians as far south as West Virginia (Siccama 1974, Siccama et al. 1982, Vogelmann 1982, Foster and Reiners 1983, Battles et al. 1992). Increasing mortality rates are evident in individuals of all size classes, and have been exacerbated by a lack of reproduction (Siccama et at. 1982).  On one peak in the Green Mountains, a mortality rate of nearly 50% was recorded among spruces between 1965-1982 (Vogelmann 1982), with mortality especially severe among high-elevation spruces on windward slopes.  Seedling production also declined by 50%, with little spruce regeneration evident.  In New Hampshire's White Mountains, a forest sampled near the Hubbard Brook Experimental Forests showed a decline in saplings from 117 stems/ha in 1965 to 33 stems/ha in 1977 (Siccama et al. 1982).  Larger trees were also affected, declining from 45 to 40 stems/ha.

High mortality rates are also evident in balsam fir (Miller-Weeks and Smoronk 1993), another essential component of Bicknell's Thrush breeding habitat.  On Camel's Hump in Vermont, Siccama et al. (1982) found that balsam fir, the dominant species there, was not filling in the "growing space" released by the death of the spruces.  Not only were relatively high numbers of fir dead or dying, but there was also an over-all decrease in growth.

The composition and structure of subalpine forests may be further altered by global warming, which is predicted to have a particularly strong impact upon ecosystems of cooler climates or high altitudes.  In temperate breeding areas, predicted temperature increases range from 3°C in southern North America up to 9°C in the northern latitudes (Davis and Botkin 1985).  Although global warming is an as-yet-unrealized threat, even minor changes in temperature and soil moisture could potentially alter montane forests dependent upon a cooler climate.  Using computer simulations, a mean annual temperature increase of as little as 2°C could result in red spruce being replaced by deciduous tree species (Davis and Botkin 1985).

Tree-line communities may be particularly vulnerable to climactic change.  Unlike other communities, which are predicted to experience a delayed response to changes, tree-line habitats are expected to undergo an extremely rapid response (Davis and Botkin 1985).  Historically, a warming trend of only 0.6°C in 1880-1950 resulted in an upward movement in the alpine treeline in Lapland, and an expansion in the distribution of broad-leaved trees in southern Finland (Erkamo 1952, Davis and Botkin 1985).  In the mid- to high-latitudes, warmer temperatures of 23°C during the last interglacial (about 120,000-80,000 years ago) resulted in broad expanses of deciduous forests extending north into areas currently occupied by mixed conifer-deciduous forests (Hohn 1980, Warrick et al. 1986).  During a period of lesser warming (about 1°C, 1,200800 years ago), Canada's boreal forests extended well north of the current timberline (Lamb 1977).

Additional threats to habitat include intensive use by outdoor recreationalists such as hikers and bikers, ski resort developments, and the construction of transmission and microwave towers (Rimmer et al. 1993).  Wind-power development may become a problem, if use of this technology becomes more widespread in the future (C. Rimmer pers. comm.).

Wintering Grounds

Deforestation and land conversion continue to rapidly reduce the amount of broad-leaf, montane forests available to Bicknell's Thrush in the Dominican Republic and Haiti (Rimmer et al. 1998).  Deforestation in Haiti is calculated to occur at an annual rate of 3.7%, with only 2-5% of the landscape still forested (Rappole 1995).  In the Dominican Republic, 1980s forest inventories indicate that 14% of the native broad-leafed forest remained (Ottenwalder 1989, Anonymous 1995), with a deforestation rate of 0.6% (Rappole 1995).

Highlands are particularly vulnerable to conversion for agricultural use (Terborgh 1977, 1980).  Terborgh (1980) reported that elevations between 1O00-2000 m in the Dominican Republic are particularly denuded.  This is a concern for Bicknell's Thrush which was found at elevations ranging from 1676 m to 1829 m during recent field investigations in the Dominican Republic (Rimmer and McFarland 1995).

The larger availability of breeding versus wintering habitat means that many neotropical migrants occur in higher densities on the wintering grounds (Terborgh 1980).  This concentration can severely amplify the effects of habitat loss, with Terborgh (1980) suggesting that the conversion of Iha of forest in the Neotropics may equal the loss of 5-8ha on the breeding grounds.  He concluded that species such as Bicknell's Thrush, which concentrate in, or use primary forests in the Neotropical highlands, will be the first to experience heavy pressure due to habitat loss, and suggested the serious prospect of insufficient habitat for many neotropical migrants by the end of the century. These conclusions were supported by Rimmer et al. (1998).  They predicted the loss of the eastern section of forest within the Dominican Republic within 2-3 years, and suggested that increasing fragmentation may affect the ability of forest fragments to support forest songbirds even sooner.

Habitat Protection

In Canada, small portions of the confirmed and potential breeding range of Bicknell's Thrush fall within the boundaries of provincial and federal parks, including the Cape Breton Highlands National Park on Cape Breton Island, Mount Carleton Provincial Park and Fundy National Park in New Brunswick, Forillon National Park, Murdochville Réserve, Parc de conservation de la Gaspésie, and Reserve Matane on the Gaspé Peninsula, and, in southern Quebec, a number of scattered parks and reserves extending from Mont Mégantic in Estrie to Parc des Grands-lardins in Charlevoix. Logging and/or mining activities are permitted in some of these parks and/or reserves, however.

In New England and New York, Bicknell's Thrush breeding habitat falls mainly within national and state forests, including Maine's Baxter State Park, Vermont's Green Mountain National Forest, New Hampshire's White Mountain National Forest (which also extends across the border into Maine), and New York's Catskill Forest Park. Additionally, in Vermont, high­altitude areas (> 762 m) are somehow protected under Act 250, a state land-use law requiring development plans on lands above 762m to undergo a rigorous review process (Kibbe 1985, C. Rimmer pers. comm.).  In New York, the Adirondacks are located on state-protected land, and camping throughout the state is prohibited on peaks above 1219m (Peterson 1988).

While 10% of the Dominican Republic and 0.3% of the Haitian landscape are under some form of conservation protection (Rappole 1995, SEA-DED 1990), activities such as timber extraction and agricultural clearing have continued largely unabated.  In the national park of Sierra de Neiba, 1995 observations estimated that deforestation had occurred on approximately 30-40% of the land; by 1997, two years after the park boundaries had been established, this had increased to 70-80% of the land (Rimmer et al. 1998). Park areas below 1600 m were found to be completely deforested. (c. Rimmerpers. comm.).