Catharus bicknelli 

Scope: Global
Language: English

Translate page into:

Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Turdidae

Scientific Name: Catharus bicknelli (Ridgway, 1882)
Common Name(s):
English Bicknell's Thrush
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 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.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2c+3c+4c ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Busby, D., Campbell, G., McFarland, K., Rimmer, C., Seutin, G., Whittam, B. & Ralston, J.
Facilitator/Compiler(s): Benstead, P., Bird, J., Harding, M., Isherwood, I., Pople, R., Taylor, J., Wege, D. & Wheatley, H.
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.

Previously published Red List assessments:

Geographic Range [top]

Range Description: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).

Countries occurrence:
Canada; Cuba; Dominican Republic; Haiti; Jamaica; Martinique; Puerto Rico; United States
Virgin Islands, U.S.
Additional data:
Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:509000
Continuing decline in extent of occurrence (EOO):YesExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:11-100Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):350
Upper elevation limit (metres):2200
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: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.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:63300-84000Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology: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).

Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):4.2
Movement patterns:Full Migrant

Threats [top]

Major Threat(s): 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 [top]

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).

Classifications [top]

1. Forest -> 1.4. Forest - Temperate
suitability:Suitable season:breeding major importance:Yes
1. Forest -> 1.6. Forest - Subtropical/Tropical Moist Lowland
suitability:Suitable season:non-breeding major importance:No
1. Forest -> 1.9. Forest - Subtropical/Tropical Moist Montane
suitability:Suitable season:non-breeding major importance:Yes
14. Artificial/Terrestrial -> 14.4. Artificial/Terrestrial - Rural Gardens
suitability:Suitable season:non-breeding major importance:No
2. Land/water management -> 2.1. Site/area management

In-Place Research, Monitoring and Planning
  Action Recovery plan:No
  Systematic monitoring scheme:No
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over entire range
  Occur in at least one PA:Yes
  Invasive species control or prevention:No
In-Place Species Management
  Successfully reintroduced or introduced beningly:No
  Subject to ex-situ conservation:No
In-Place Education
  Subject to recent education and awareness programmes:No
  Included in international legislation:Yes
  Subject to any international management/trade controls:No
1. Residential & commercial development -> 1.3. Tourism & recreation areas
♦ timing:Past, Likely to Return ♦ scope:Minority (<50%) ♦ severity:No decline ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

11. Climate change & severe weather -> 11.1. Habitat shifting & alteration
♦ timing:Future ♦ scope:Whole (>90%) ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.2. Small-holder farming
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 6 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

5. Biological resource use -> 5.3. Logging & wood harvesting -> 5.3.3. Unintentional effects: (subsistence/small scale) [harvest]
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 6 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

6. Human intrusions & disturbance -> 6.1. Recreational activities
♦ timing:Future ♦ scope:Unknown ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 2. Species Stresses -> 2.2. Species disturbance

8. Invasive and other problematic species, genes & diseases -> 8.1. Invasive non-native/alien species/diseases -> 8.1.2. Named species [ Rattus rattus ]
♦ timing:Ongoing ♦ scope:Unknown ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

9. Pollution -> 9.5. Air-borne pollutants -> 9.5.1. Acid rain
♦ timing:Past, Likely to Return ♦ scope:Whole (>90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
1. Research -> 1.5. Threats

Bibliography [top]

Anon. 2006/2007. Case study: Bicknell's Thrush. Bird Conservation: 10.

Atwood, J. L.; Rimmer, C. C.; McFarland, K. P.; Tsai, S. H.; Nagy, L. R. 1996. Distribution of Bicknell's Thrush in New England and New York. Wilson Bulletin 108: 650-661.

Campbell, G. 2011. High Elevation Landbird Program 2010 report. Bird Studies Canada, Sackville.

COSEWIC. 2009. COSEWIC assessment and status report on the Bicknell's Thrush Catharus bicknelli in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa.

Erickson, L. 2011. Rats! A menace for Bicknell's thrushes. Birdscope Spring 2011: 1.

Garrido, O. H.; García Montaña, F. 1975. Catálogo de las aves de Cuba. Academia de Ciencias de Cuba, La Habana.

Hale, S. R. 2006. Using satellite imagery to model distribution and abundance of Bicknell's Thrush (Catharus bicknelli) in New Hampshire's White Mountains. The Auk 123(4): 1038-1051.

IBTCG. 2010. A Conservation Action Plan for Bicknell’s Thrush (Catharus bicknelli). International Bicknell’s Thrush Conservation Group.

IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-3. Available at: (Accessed: 07 December 2016).

Lambert, J.D.; McFarland, K. P.; Rimmer, C.C.; Faccio, S.D.; Atwood, J. L. 2005. A practical model of Bicknell's Thrush distribution in the northeastern United States. Wilson Bulletin 117: 1-11.

Ouellet, H. 1993. Bicknell's Thrush: taxonomic status and distribution. Wilson Bulletin 105: 545-572.

Phillips, A. R. 1991. The known birds of North and Middle America. Allan R. Phillips., Denver.

Raffaele, H., Wiley, J., Garrido, O., Keith, A., and Raffaele, J. 1998. Birds of the West Indies. Christopher Helm, London.

Ralston, J., King, D.I., DeLuca, W.V., Niemi, G.J., Glennon, M. J., Scarl, J.C., and Lambert, J.D. 2015. Analysis of combined data sets yields trend estimates for vulnerable spruce-fir birds in northern United States. Biological Conservation 187: 270-278.

Ralston, J. & Kirchman, J. J. 2013. Predicted range shifts in North American boreal forest birds and the effect of climate change on genetic diversity in blackpoll warblers (Setophaga striata). Conservation Genetics 14: 543-555.

Rich, T.D., Beardmore, C.J., Berlanga, H., Blancher, P.J., Bradstreet, M.S.W., Butcher, G.S., Demarest, D.W., Dunn, E.H., Hunter, W.C., Inigo-Elias, E.E., Martell, A.M., Panjabi, A.O., Pashley, D.N., Rosenberg, K.V., Rustay, C.M., Wendt, J.S. and Will, T.C. 2004. Partners in flight: North American landbird conservation plan. Cornell Lab of Ornithology, Ithaca, NY.

Rimmer, C. 1996. A closer look: Bicknell's Thrush. Birding 28: 119-123.

Rimmer, C. C.; McFarland, K. P.; Goetz, J. E. 1999. Demographics and ecology of Bicknell's Thrush and montane forest birds in the Dominican Republic.

Rodenhouse, N. L.; Matthews, S. N.; McFarland, K. P.; Lambert, J. D.; Iverson, L. R.; Prasad, A.,; Sillett, T. S.; Holmes, R. T. 2008. Potential effects of climate change on birds of the Northeast. Mitigation and Adaptation Strategies for Global Change 13: 517-540.

Citation: BirdLife International. 2016. Catharus bicknelli. The IUCN Red List of Threatened Species 2016: e.T22728467A94987334. . Downloaded on 22 September 2018.
Disclaimer: To make use of this information, please check the <Terms of Use>.
Feedback: If you see any errors or have any questions or suggestions on what is shown on this page, please provide us with feedback so that we can correct or extend the information provided