Bicknell's Thrush Catharus bicknelli


Justification of Red List Category
This species is listed as Vulnerable because its population is suspected to be in rapid decline overall, on the basis of regional trend data and knowledge of on-going threats that are causing habitat loss and degradation in both its breeding and wintering ranges.

Population justification
The current population estimate for the species in Canada is between 40,570 and 49,258 individuals (COSEWIC 2009), with global estimates of 95,000-126,000 individuals (IBTCG 2010), probably including c.63,300-84,000 mature individuals.

Trend justification
Breeding population trend data for the species are sparse, but generally indicate declines, especially in core and northern parts of the range. Annual declines of 7-19% have been documented in parts of the species’s breeding range (IBTCG 2010). A rapid population decline is suspected overall, based on these data, and owing to the on-going loss and conversion of the species's wintering habitat. In the past, acid rain may have reduced available habitat. Potential future threats include global warming.

Distribution and population

Catharus bicknelli breeds patchily in south-east Quebec and the Maritime provinces, Canada, and eastern New York and northern New England, USA (Phillips 1991, Ouellet 1993, Atwood et al. 1996). There are 20,000-50,000 adults in the USA  (C. C. Rimmer in litt. 1998, 1999, K. McFarland in litt. 1999) and 1,000-3,000 birds in the Maritime provinces (D. Busby in litt. 1999), but there have been local extinctions (C. C. Rimmer in litt. 1998, 1999). It migrates along the coast to winter in the Caribbean (Raffaele et al. 1998). The stronghold is the Dominican Republic (especially the Sierra de Baoruco and Cordillera Central) and possibly Haiti (Raffaele et al. 1998, Rimmer et al. 1999). It may also winter in the Blue Mountains of Jamaica, and small numbers occur in Puerto Rico and Dominica. There are three records from Cuba, including one in the Sierra Maestra in 1999 (Garrido and Garcia Montaña 1975, C. C. Rimmer in litt. 1998, 1999, G. Seutin in litt. 1999). The population is suspected to be in rapid decline overall. Population trend data show mixed results, but annual declines of 7-19% have been documented in parts of the species’s breeding range (IBTCG 2010). An analysis of several combined data sets revealed an overall decline of c.2.5%/year in New York and New England (Ralston et. al. 2015). Surveys (conducted through the High Elevation Landbird Program) in New Brunswick and Nova Scotia recorded apparent declines of c.16%/year and 11%/year respectively between 2002 and 2010 (Campbell 2011). Results from the second Maritime Breeding Bird Atlas show a greater than 40% decline in the distribution of the species between 1999 and 2009 (COSEWIC 2009). The current population estimate for the species in Canada is between 40,570 and 49,258 birds (COSEWIC 2009), with global estimates of 95,000-126,000 birds (IBTCG 2010).


It breeds in dense montane forests (above 900 m) of balsam fir Abies balsamae and red spruce Picea rubens, usually near the treeline (Atwood et al. 1996, Rimmer 1996), but occupies less than 75% of available habitat (C. C. Rimmer in litt. 1998, 1999). In Canada, it also inhabits regenerating clear-cuts and coastal areas with spruce-fir at low elevations (Atwood et al. 1996). In winter, it occurs in moist broadleaved and mixed pine-broadleaved montane forests and secondary woodlands (Rimmer 1996, Raffaele et al. 1998, Rimmer et al. 1999). It nests in June-July (present on breeding grounds May-September), sometimes with high failure rates (Rimmer 1996). It may sexually segregate in winter, with females in poorer quality habitats (C. C. Rimmer in litt. 1998, 1999).


Acid precipitation may have damaged breeding habitat in the 1960s and 1970s (Phillips 1991, Rimmer 1996). Projected climate change is expected to result in decreases in the extent of the species's breeding habitat (C. C. Rimmer in litt. 1998, 1999, K. McFarland in litt. 1999, Rodenhouse et al. 2008, Ralston and Kirchman 2013). Ski-resort, communication and wind-power developments potentially threaten local populations (Atwood et al. 1996, Rimmer 1996). In Quebec, the widespread practice of thinning renders habitat unsuitable (G. Seutin in litt. 1999). Agricultural conversion, logging and charcoal production are rapidly clearing and fragmenting winter habitat (Atwood et al. 1996, C. C. Rimmer in litt. 1998, 1999). Invasive rats Rattus rattus  pose a threat through predation in the winter range (Erickson 2011).

Conservation actions

Conservation Actions Underway
CMS Appendix II. SPAW Protocol Annex 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 protected (Rimmer et al. 1999), but recent funding requests for management were turned down. Management and protection of existing reserves and parks is now inadequate (C. Rimmer in litt. 2003). A predictive model has been developed and used to generate a population estimate for this species within New Hampshire (Hale 2006), 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 decisions (Lambert et al. 2005). New (and expansion of existing) ski-resorts are developed following environmental impact assessment, in a way that mitigates against habitat loss and disturbance (Anon 2006). One development established a fund for protecting the wintering grounds (Anon 2006). A conservation action plan has been produced for the species, with the overall goal of achieving a 25% population increase during the period 2011-2060 and no further net loss in distribution (IBTCG 2010).

Conservation Actions Proposed
Clarify distribution and migration details (Atwood et al. 1996, Rimmer 1996). Refine estimates of population size (Atwood et al. 1996, Rimmer 1996), potentially by using an existing predictive model and applying it to new areas. Evaluate human impacts on breeding birds (C. C. Rimmer in litt. 1998, 1999). Clarify winter segregation (C. C. Rimmer in litt. 1998, 1999). Develop strategies to maintain dense stands of regenerating balsam fir in Quebec. Develop management plans for existing, and designate new, reserves in the Dominican Republic (C. C. Rimmer in litt. 1998, 1999, Rimmer et al. 1999).


16-19 cm. Small thrush. Buffy-brown upperparts. Bold black spotting on sides of throat and creamy-buff breast. Rest of underparts white. Greyish cheeks and lores, and dark reddish-brown tail. Similar spp. Smaller than Grey-cheeked Thrush C. minimus, and browner above with paler lores, buffier on breast and has yellow (not pink) on lower mandible. Swainson's Thrush C. ustulatus shows distinct eye-ring. Veery C. fuscescens is redder above and more finely spotted below. Hermit Thrush C. guttatus shows rufous tail. Voice Song, high-pitched chook-chook wee-o wee-o wee-o-tee-t-ter-ee descending at end. Call, harsh slurred whistle. Hints Best located by song in breeding areas.


Text account compilers
Benstead, P., Bird, J., Harding, M., Isherwood, I., Pople, R., Taylor, J., Wege, D. & Wheatley, H.

Busby, D., Campbell, G., McFarland, K., Rimmer, C., Seutin, G., Whittam, B. & Ralston, J.

Recommended citation
BirdLife International (2020) Species factsheet: Catharus bicknelli. Downloaded from on 06/06/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from on 06/06/2020.