Table of Contents
Overview
Distribution
Range Description
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National Distribution
Canada
Origin: Native
Regularity: Regularly occurring
Currently: Present
Confidence: Confident
Type of Residency: Breeding
United States
Origin: Native
Regularity: Regularly occurring
Currently: Present
Confidence: Confident
Type of Residency: Breeding
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Global Range: (250-20,000 square km (about 100-8000 square miles)) BREEDING: eastern New York (south to the Catskill Mountains), Massachusetts (formerly, on Mount Greylock), central and northern Vermont, northern New Hampshire, Maine, southern Nova Scotia (has disappeared from Seal Island), Magdalen Islands (at least formerly), Gaspe Peninsula, interior highlands of New Brunswick, and (formerly) along the north shore of the Gulf of St. Lawrence from Natashquan, Quebec, east to Cape Saint Charles, southern Labrador (AOU 1957, Rimmer et al. 1993). In the U.S., mainly at elevations above 3000 ft; in 1992, found on 4 peaks lower than 3000 ft. In Quebec, elevations of 175-1160 (Ouellet 1993). NON-BREEDING: poorly documented; known from Hispaniola, Cuba, Puerto Rico, and St. Croix; winter stronghold almost certainly is the Dominican Republic (Rimmer 1996); not known from Central or South America (Ouellet 1993). Migration records encompass eastern coastal states of U.S. and Bahamas (Ouellet 1993).
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Physical Description
Diagnostic Description
Smaller and typically richer brown dorsally than the gray-cheeked thrush; tail color (with various amounts of chestnut) contrasts with the back color in Bicknell's whereas there is little contrast in gray-cheeked thrush; pale area at base of bill is yellowish in Bicknell's, fleshy-pink in gray-cheeked; white of ventral region is duller than in gray-cheeked thrush; songs differ as well, with those of Bicknell's ending on an even or ascending pitch whereas the gray-cheeked's descends (Rimmer et al. 1993, Ouellet 1993). However, Bicknell's thrush from the Gaspe Peninsula lacks bright yellow on the mandible, and some Newfoundland gray-cheeked thrushes have more extensively pale mandibles, "warm" plumage tones, and appear to have a chestnut tail (McLaren 1995). In migration, Bicknell's thrush and gray-cheeked thrush probably cannot be reliably separated without specimens in hand.
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Ecology
Habitat
Habitat and Ecology
Systems
- Terrestrial
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Comments: In New England and New York, inhabits montane forests, primarily areas dominated by stunted balsam fir and red spruce at elevations above 3000 ft (Rimmer et al. 1993). Habitats in Canada include mountaintop and dense coastal coniferous forests as well as mixed second-growth regenerating stands (Rimmer 1996). In southern Quebec, occurs mainly in second growth stands characterized by relatively young conifers of small size (balsam fir, white spruce) intermixed with a variety of deciduous species typical of second-growth regeneration (Prunus sp., BETULA sp., Amelanchier sp., Acer spicatum, POPULUS sp.) following forest fires or clear cutting; trees seldom exceed 10 m in height (Ouellet 1993). Nests generally are situated close to the trunk in the upper half of a small-to-medium-sized fir or spruce, typically in conifer thickets, often on steep slopes (Rimmer 1996). In migration and winter also in deciduous forest, forest borders, open woodland, second growth, and scrub. Winter habitat may be restricted to primary tropical forest (Rimmer et al. 1993). Occurred at fairly high densities in moist, broad-leafed montane forest in the Dominican Republic (Rimmer 1996).
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Migration
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Migrates through the U.S. mainly east of the Alleghenies (AOU 1957); through eastern coastal states (Ouellet 1993). Departs from northern New England in late Septemeber or early October, returns in mid- to late May (Rimmer 1996).
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Trophic Strategy
Comments: Eats mainly insects and other invertebrates and small fruits (Terres 1980).
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Population Biology
Global Abundance
10,000 to >1,000,000 individuals
Comments: Total breeding population probably is 7500-15,000 pairs (Rimmer 1996). In June-July surveys in 1992, populations ranged from only one or two pairs on 70 peaks to as many as 250 pairs on Mount Mansfield in Vermont (Rimmer et al. 1993; Audubon, November-December 1993, pp. 116-118).
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General Ecology
At Mount Mansfield, Vermont, density was estimated at about 50-60 pairs/40 ha in optimal habitat (Rimmer 1996).
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Life History and Behavior
Cyclicity
Comments: Singing activity is most frequent in early to mid-June (Rimmer et al. 1993).
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Life Expectancy
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Lifespan, longevity, and ageing
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Reproduction
Eggs are laid in June (mostly) and July. Clutch size is 3-6 (average 3-4). Incubation, by female, lasts 12-14 days. Young are tended by both parents, leave nest at 11-13 days. Pairs with failed nests early in the season may renest. Causes of nest failure include predation by red squirrel and blue jay and desertion (Rimmer 1996).
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Molecular Biology and Genetics
Molecular Biology
Barcode data: Catharus bicknelli
There are 12 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
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Statistics of barcoding coverage: Catharus bicknelli
Public Records: 12
Species: 14
Species With Barcodes: 1
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Contributor/s
Justification
History
- 2004Vulnerable
- 2000Vulnerable
- 1994Not Recognized
- 1988Not Recognized
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National NatureServe Conservation Status
Canada
Rounded National Status Rank: N3B - Vulnerable
United States
Rounded National Status Rank: N4B - Apparently Secure
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NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
Reasons: Breeds in the northeastern U.S. and southeastern Canada, winter records are from the West Indies; apparently stable in New York/New England, but overall conservation status is not well known.
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Trends
Population
Population Trend
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Global Short Term Trend: Unknown
Comments: May be declining in north and south, but distribution in New England and New York has not undergone significant recent change; conservation status is uncertain (Rimmer et al. 1993).
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Threats
Threats
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Comments: Threatened by the damaging effects of acid precipitation and airborne pollution, habitat loss from ski area development and transmission tower construction, and overuse by hikers; global climate change is a potential threat (Rimmer et al. 1993). Wind power development is an increasing threat in parts of the breeding range (Rimmer 1996). Deforestation in the winter range probably has eliminated habitat (Rimmer 1996).
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Management
Conservation Actions
CMS Appendix II. There is much research activity in the breeding range and, increasingly, the Caribbean. Some important breeding areas and c.50% of sites in the Dominican Republic are actively protected9, but recent funding requests for management were turned down. Management and protection of existing reserves and parks is now inadequate12. A predictive model has been developed and used to generate a population estimate for this species within New Hampshire13, and a more general model has been used to predict distribution in the north-eastern USA in order to inform and plan habitat management/alteration decisions15. New (and expansion of existing) ski-resorts are developed following environmental impact assessment, in a way that mitigates against habitat loss and disturbance14. One development established a fund for protecting the wintering grounds14. Conservation Actions Proposed
Clarify distribution and migration details1,8. Refine estimates of population size1,8, potentially by using an existing predictive model and applying it to new areas. Evaluate human impacts on breeding birds10. Clarify winter segregation10. Develop strategies to maintain dense stands of regenerating balsam fir in Quebec. Develop management plans for existing, and designate new, reserves in the Dominican Republic9,10.
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Biological Research Needs: Determine population trends, demographics, impacts of habitat degradation, migration routes and ecology, and winter ecology (Rimmer 1996).
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Wikipedia
Bicknell's Thrush
The Bicknell's Thrush, Catharus bicknelli, is a medium-sized thrush, at 17.5 cm (6.9 in) and 28 g (1 oz). It was named after Eugene Bicknell, an American amateur ornithologist, who discovered the species on Slide Mountain in the Catskills in the late 19th century.
Adults are olive-brown on the upperparts, slightly redder on the tail. The underparts are white with gray on the flanks; the breast is greyish brown with dark spots. They have pink legs, a faint grey eye ring, and gray cheeks. They average slightly smaller than the very similar Gray-cheeked Thrush but are all but indistinguishable in outward appearance. Together, Gray-cheeked and Bicknell's Thrush form a cryptic species pair, and were indeed formerly considered conspecific [1]. The song is a jumbled series of flute-like tones ending on a higher note.
Their breeding habitat is the coniferous forests in southeastern Quebec to Nova Scotia and the sky islands of northern New England and New York state. It is the rarest and most secretive of the breeding thrushes in North America and it is the only bird whose breeding is restricted to the Northeastern part of the continent. They usually breed at higher elevations, normally nesting above 915 m (3,000 ft).[1]
Bicknell's Thrushes have an unusual mating system in which females mate with more than one male. Such a practice is not known to occur in other thrushes.[2] As many as four males perform duties connected with one nest, including bringing food for the nestlings. The nest itself is typically a bulky cup, close to the trunk of a conifer. Nestlings grow rapidly, developing in 12 days from peanut-sized hatchlings to completely feathered adult-sized birds. Ticks, blowflies, and lice are some of the parasites with which Bicknell's Thrush must contend. The red squirrel is the main predator of eggs and nestlings, according to breeding ecology studies.[2] Other predators include the Sharp-shinned Hawk, the long-tailed weasel, and the Northern Saw-whet Owl.
The thrush's diet consist mainly of insects, but wild fruits are added in late summer, during migration, and on the wintering grounds. They usually forage on the forest floor, but also catch flies, and glean insects from the foliage of trees.
These birds migrate to the West Indies, (the Greater Antilles), with an estimated 90% of the individuals wintering on Hispaniola [2]. Bicknell's and Gray-cheeked Thrush, along with the Veery, make up a close-knit group of migrant species (Winker & Pruett, 2006).
Its numbers are declining in some parts of its already limited range as a result of habitat degradation. Scientists believe that industrial pollution is one of the main reasons for the decline of the red spruce, an important element in Bicknell’s Thrush habitat in the United States. Airborne heavy metals may also damage high-elevation forests in the northeastern United States. Furthermore, based on expected substantial carbon dioxide increases by the end of the century, scientists predict a radical reduction of balsam fir forest in the eastern United States. If average global temperatures increase and forests change as much as predicted, Bicknell’s Thrush habitat is very likely to be altered in ways that may seriously affect the species’ survival.
Other potential threats to Bicknell’s Thrush habitat are the development of recreational skiing and summer sports areas, increasing numbers of telecommunication towers on mountaintops, cyclical spruce budworm outbreaks, and commercial forestry operations. Industrial forestry practices, although possibly harmful, may be modified to aid in conservation efforts to protect Bicknell’s Thrush. While more study is needed, the bird’s apparent acceptance of certain commercial second-growth forest gives promise to possibilities of “growing” Bicknell’s Thrush habitats in the future.
There is also considerable concern about the degradation of Bicknell’s Thrush’s wintering habitats. The Dominican Republic’s native forests are under considerable pressure from naturally occurring events such as hurricanes, as well as changes from agricultural activities, particularly at low altitudes. The forested lands of Haiti have been almost completely eliminated, and in Cuba, most of the known suitable habitat exists only in protected parklands.[2]
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References
- ^ http://www.fws.gov/r5gomp/gom/habitatstudy/metadata/Bicknell's_thrush_model.htm
- ^ a b c http://www.hww.ca/hww2.asp?cid=7&id=28
- BirdLife International (2004). Catharus bicknelli. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. RangeMap Database entry includes a range map and justification for why this species is vulnerable.
- Winker, Kevin & Pruett, Christin L. (2006): Seasonal migration, speciation, and morphological convergence in the avian genus Catharus (Turdidae). Auk 123(4): 1052–1068. [Article in English with Spanish abstract] DOI: 10.1642/0004-8038(2006)123[1052:SMSAMC]2.0.CO;2 PDF fulltext
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Names and Taxonomy
Taxonomy
Comments: Formerly included as a subspecies of C. minimus; elevated to full species status by Ouellet (1993) (see also McLaren 1995); not known to intergrade/hybridize with C. minimus. AOU (1995) accepted full species status for C. bicknelli Formerly placed in genus Hylocichla (AOU 1983).
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