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Dusky Tetraka

Crossleyia tenebrosa

Abstract

Dusky Tetraka Crossleyia tenebrosa has most recently been assessed for The IUCN Red List of Threatened Species in 2020. Crossleyia tenebrosa is listed as Data Deficient.


The Red list Assessmenti

Last assessed

15 June 2020

Scope of assessment

Global

Population trend

Decreasing

Number of mature individuals

U

Population in detail

Habitat and ecology

Forest

Habitat and ecology in detail

Geographic range

+−
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  • Extant (resident)

BirdLife International and Handbook of the Birds of the World (2016) 2000. Crossleyia tenebrosa. The IUCN Red List of Threatened Species. Version 2024-2
Geographic range in detail

Taxonomy

Kingdom

Animalia

Phylum

Chordata

Class

Aves

Order

Passeriformes

Family

Bernieridae

Genus

Crossleyia

Scientific name

Crossleyia tenebrosa

Authority

(Stresemann, 1925)

Synonyms

Bernieria tenebrosa (Stresemann, 1925)

Bernieria tenebrosus BirdLife International (2004)

Phyllastrephus tenebrosus tenebrosus BirdLife International (2000)

Phyllastrephus tenebrosus tenebrosus Collar et al. (1994)

Phyllastrephus tenebrosus tenebrosus Sibley and Monroe (1990, 1993)

Phyllastrephus tenebrosus tenebrosus Collar and Andrew (1988)

Common names

English

Dusky Tetraka, Dusky Greenbul

French

Bulbul obscur

Taxonomic sources

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

14-15 cm. Small, rotund, terrestrial babbler-like bird. Dull dark earth-brown upperparts, with no green or yellow. Bright yellow eye-ring and loral streak to eye, and oval patch on throat. Breast similar dark brown to upperparts, belly paler. Legs stout. Bill and tail rather short. Bill mostly pale pink; pinkish-grey legs. Similar spp. From other Malagasy greenbuls by largely terrestrial habits, dark upper- and underparts, short tail, narrower yellow eye-ring and throat patch, and stronger legs. Hints Hops along ground in lowland rainforest, often in rather open areas.

Taxonomic notes

Crossleyia tenebrosa (del Hoyo and Collar 2016) was previously listed as Bernieria tenebrosa.

Assessment Information

Global Assessment

IUCN Red List Category and Criteria - Global Assessment

Data Deficient 

ver 3.1

Date assessed

15 June 2020

Year published

2020

Year last seen

Previously published Red List assessments

Regional assessments

    Assessor(s)

    BirdLife International

    Reviewer(s)

    Wheatley, H.

    Contributor(s)

    Ekstrom, J., Evans, M., Hawkins, F., Hermes, C., Lambert, F., Mills, S.L., Rabenandrasana, M., Schulenberg, T., Shutes, S., Starkey, M., Symes, A., Taylor, J. & Westrip, J.R.S.

    Facilitator(s) / Compiler(s)

    Clark, J.

    Partner(s) / Institution(s)

    Authority / Authorities

    IUCN SSC Bird Red List Authority (BirdLife International)

    Justification

    The status of this species is highly uncertain. There is insufficient information to estimate range, population size or trend, and consequently the species is classified as Data Deficient.

    Geographic Range

    Native

    Extant (resident)

    Madagascar

    Number of locations

    Upper elevation limit

    950 metres

    Lower elevation limit

    200 metres

    Estimated area of occupancy (AOO) (km²)

    Continuing decline in area of occupancy (AOO)

    Yes

    Extreme fluctuations in area of occupancy (AOO)

    No

    Estimated extent of occurrence (EOO) (km²)

    50600

    Continuing decline in extent of occurrence (EOO)

    Unknown

    Extreme fluctuations in extent of occurrence (EOO)

    No

    Continuing decline in number of locations

    Unknown

    Extreme fluctuations in the number of locations

    No

    Range Description

    Crossleyia tenebrosa is found only in lowland rainforest in eastern Madagascar, where it is apparently extremely scarce (ZICOMA 1999). The species has previously been widely misidentified (Morris and Hawkins 1998), and no reliable sightings have been recorded in the last 20 years (M. Mills in litt. 2020).  Previous records have been from Marojejy (775 m), Betampona Strict Nature Reserve (below 600 m) and Zahamena (c.400 m), while records from Masoala peninsula, Ranomafana National Park and Analamazaotra Special Reserve require confirmation (ZICOMA 1999, Britt et al. 2003, Hawkins and Sartain 2013). Specimens are known from the central-east (Forêt Sihanaka, near Zahamena, and Mantadia [ZICOMA 1999], as well as Betaolona Forest and Lakato Forest near Moramanga [Hawkins and Sartain 2013]). During inventories of protected areas at Andringitra, Anjanaharibe-South, Andohahela and Marojejy, the species has been recorded only once and never mist-netted, despite around 10 months of survey effort and substantial mist-netting effort (ZICOMA 1999). It was thought to have the most restricted range of the eastern Malagasy rainforest species (ZICOMA 1999), but now the extent of its current range is not fully known. 


    Population

    Current population trend

    Decreasing

    Number of mature individuals

    U

    Population severely fragmented

    Unknown

    Continuing decline of mature individuals

    Unknown

    Extreme fluctuations

    No

    No. of subpopulations

    Continuing decline in subpopulations

    Unknown

    Extreme fluctuations in subpopulations

    Unknown

    All individuals in one subpopulation

    Unknown

    No. of individuals in largest subpopulation

    Description

    There have been no reliable sightings of this species for the last 20 years (M. Mills in litt. 2020), and as such the population size of this species is now unknown.

    Trend Justification: The species's population is suspected to be declining in line with the clearance and degradation of lowland rainforest in eastern Madagascar. The likely rate of decline, however, has not been estimated.

    Habitat and Ecology

    System

    Habitat type

    Forest

    Generation length (years)

    2.7 years

    Congregatory

    Movement patterns

    Not a Migrant

    Continuing decline in area, extent and/or quality of habitat

    Yes

    Habitat and Ecology

    This still-mysterious species is found in the understorey of both lowland and mid-altitude (up to 950 m) undisturbed, humid, evergreen forest. It forages for small insects, larvae and small spiders, both on the ground and in low shrubs, while it may avoid dense undergrowth (Randriamanindry 1995, Morris and Hawkins 1998). It often occurs with other ground or low-understorey species, and has been observed recently in mixed-species foraging flocks, where there were usually fewer C. tenebrosa than Spectacled Tetraka C. zosterops or Common Tetraka C. madagascariensis (Randriamanindry 1995, Morris and Hawkins 1998).


    Classification scheme

    HabitatsSeasonSuitabilityMajor importance
    1. Forest1.6. Forest - Subtropical/Tropical Moist LowlandResidentSuitableYes

    Threats

    Agriculture & aquaculture

    • Annual & perennial non-timber crops

    Biological resource use

    • Logging & wood harvesting

    Threats

    Its habitat is being reduced in extent, the principal threat coming from slash-and-burn cultivation by subsistence farmers, which results in progressively more degraded regrowth and leads eventually to bracken-covered areas or grassland (Du Puy and Moat 1996). Much of the eastern coastal plain has either already been cleared or is covered by highly degraded forest (Jenkins 1987), remaining habitat is under pressure from the increasing human population (Jenkins 1987), and commercial logging is an additional threat in some areas (A.F.A. Hawkins in litt. 1995). If present trends continue, the remaining forest will disappear within decades (Du Puy and Moat 1996).

    Classification scheme

    ThreatsTimingStressesScopeSeverityInvasive speciesVirus
    2. Agriculture & aquaculture2.1. Annual & perennial non-timber crops2.1.1. Shifting agricultureOngoing
    1. Ecosystem stresses1.1. Ecosystem conversion
    1.2. Ecosystem degradation
    		Majority (50-90%)Slow, Significant Declines
    5. Biological resource use5.3. Logging & wood harvesting5.3.4. Unintentional effects: (large scale) [harvest]Ongoing
    1. Ecosystem stresses1.1. Ecosystem conversion
    1.2. Ecosystem degradation
    		Minority (<50%)Slow, Significant Declines

    Use and Trade

    Use and Trade

    Conservation Actions

    In-place research and monitoring

    • Action Recovery Plan : No
    • Systematic monitoring scheme : No

    In-place land/water protection

    • Conservation sites identified : Yes, over entire range
    • Occurs in at least one protected area : Yes
    • Invasive species control or prevention : No

    In-place species management

    • Successfully reintroduced or introduced benignly : No
    • Subject to ex-situ conservation : No

    In-place education

    • Subject to recent education and awareness programmes : No
    • Included in international legislation : No
    • Subject to any international management / trade controls : No

    Conservation Actions

    Conservation Actions Underway
    This species is known from only three eastern Malagasy IBAs (ZICOMA 1999), including the following protected areas: Marojejy National Park, Masoala National Park, Zahamena National Park (Morris and Hawkins 1998).

    Conservation Actions Proposed
    Carry out surveys to locate populations and estimate population size. Establish habitat requirements and other factors limiting its distribution/population, in order to better predict its likely distribution and population size. Monitor the clearance and degradation of forest within its potential range. Increase the area of suitable habitat that has protected status.

    Conservation actions classification scheme

    Conservation Actions NeededNotes
    1. Land/water protection1.1. Site/area protectionIncrease the area of suitable habitat that has protected status. </P>

    Research classification scheme

    Research NeededNotes
    1. Research1.2. Population size, distribution & trendsLocate other populations. </P>
    1.3. Life history & ecologyEstablish habitat requirements and other factors limiting its distribution/population, in order to better predict its likely distribution and population size. </P>
    3. Monitoring3.4. Habitat trendsMonitor the clearance and degradation of forest within its potential range. </P>

    Bibliography

    Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S.G., Symes, A., Taylor, J., Şekercioğlu, Ç.H. and Butchart, S.H.M. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology 34(5): 1252-1261.

    Britt, A., Iambana, B. R., Welch, C. R. and Katz, A. S. 2003. Restocking of Varecia variegata variegata in the Réserve Naturelle Intégrale de Betampona. In: S. M. Goodman and J. P. Benstead (eds), The Natural History of Madagascar, pp. 1545–1551. The University of Chicago Press, Chicago, USA.

    Du Puy, D. J.; Moat, J. 1996. A refined classification of the primary vegetation of Madagascar based on the underlying geology: using GIS to map its distribution and to assess its conservation status. In: Lourenço, W.R. (ed.), Proceedings of the International Symposium on the biogeography of Madagascar, pp. 205-218. ORSTOM, Paris.

    Global Forest Watch. 2020. Interactive Forest Change Mapping Tool. Available at: http://www.globalforestwatch.org/.

    Hawkins, A. F. A.; Sartain, A. 2013. Dusky Tetraka, Xanthomixis tenebrosa. In: Safford, R. J.; Hawkins, A. F. A. (ed.), The Birds of Africa. Volume VIII: The Malagasy Region, pp. 728-730. Christopher Helm, London.

    IUCN. 2020. The IUCN Red List of Threatened Species. Version 2020-3. Available at: www.iucnredlist.org. (Accessed: 10 December 2020).

    Jenkins, M. D. 1987. Madagascar: an environmental profile. International Union for Conservation of Nature and Natural Resources, Cambridge, U.K.

    Morris, P.; Hawkins, F. 1998. Birds of Madagascar: a photographic guide. Pica Press, Robertsbridge, UK.

    Randriamanindry, J. J. 1995. The Dusky Greenbul Phyllastrephus tenebrosus in the Zahamena Strict Reserve, Madagascar. Working Group on Birds in the Madagascar Region Newsletter 5: 1.

    ZICOMA. 1999. Zones d'Importance pour la Conservation des Oiseaux a Madagascar.

    External Data

    Images and External Links

    iNaturalist.org observations

    Search sites for species

    GooglePicSearchFishBaseBirdLife InternationalNatureServe ExplorerGBIF - Global Biodiversity Information Facility Encyclopedia of LifeCatalogue of Life (Species2000)

    CITES Legislation from Species+

    Data Source

    The information below is from the Species+ website.

    Ex situ data from Species360

    Data Source

    The information below is from Species360's Zoological Information Management System (ZIMS)

    Studies and Actions from Conservation Evidence

    Data Source

    The information below is from the Conservation Evidence website.

    Search terms: "Crossleyia tenebrosa", "Bernieridae"

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