Archived 2010-2011 topics: Unicoloured Thrush (Turdus haplochrous): new information requested

Unicoloured Thrush Turdus haplochrous is known from only a few localities in south-east Beni and west Santa Cruz, north Bolivia. It is currently listed as Near Threatened under criterion C2 because the global population is assumed to be small owing to the small number of records.

The species occurs in seasonally flooded riverine forest (várzea), semi-open forest and semi-deciduous woodland at 250-350 m. This habitat is widespread in the Bolivian lowlands and is not currently subject to particular threats. However, the species’s patchy range implies that future changes in land-use could lead to an increase in threat status. With so little known about the species, assigning it to a Threatened category on the IUCN Red List is problematic. Given the lack of recent records its global population may be extremely small and the species may warrant listing in a higher threat category, but alternatively it may simply have been overlooked and given that it has a potentially large range (the current Extent of Occurrence is estimated at 192,000 km2) then it could be Least Concern. Until better data is available to inform this decision it may be necessary to give a listing of Data Deficient.

Comments on the species’s status are most welcome.

(This discussion was started as part of the 2010 Red List update)

Unicoloured Thrush Turdus haplochrous es conocida sólo de unas pocas localidades en el sureste de Beni y al oeste de Santa Cruz, al norte de Bolivia. En la actualidad está clasificada como Casi Amenazado en el criterio C2, porque la población mundial se supone que es pequeña debido al reducido número de registros.

La especie se produce en los bosques ribereños estacionalmente inundados (Várzea), semi-abiertos y los bosques semi-deciduos entre los 250-350 m. Este hábitat está muy extendido en las tierras bajas bolivianas y no está sujeto actualmente a amenazas. Sin embargo, la distribución fragmentada de la especie implica que los futuros cambios en el uso de la tierra podrían conducir a un aumento en su estado de amenaza. Con tan poco conocimiento acerca de la especie, la asignación de una categoría de amenaza en la Lista Roja de la UICN es problemática. Dada la falta de registros recientes de su población mundial se piensa que puede ser muy pequeña lo que podría justificar su inclusión en una categoría de amenaza superior, pero, alternativamente, se puede simplemente pensar que se han pasado por alto su registro, y dado que tiene un amplio rango de distribución potencial (la distribución actual se calcula en 192.000 km2), entonces podría ser de menor preocupación. Hasta disponer de mejores datos para evaluar a la especie se la mantiene en una categoría de Datos Insuficientes.

Se requieren comentarios sobre del estado de la especie en la actualidad.


3 Responses to Archived 2010-2011 topics: Unicoloured Thrush (Turdus haplochrous): new information requested

  1. Simon Mitchell says:

    During a six week period working on I a Blue-throated Macaw site about 75km NNW of Trinidad had single a record which I was fairly certain of. This was in fact the only Thrush sp. I saw during my entire time on the site. (I can will have to refer to someone for the exact Lat / Long co-ordinated). I have also heard (from Daniel Lane, LSU) that there are other reports of the species in the area immediately around Trinidad itself.
    It is also worth making the point that since no fieldguide currently exists for Bolivia and Ridgley & Tudor only has a text desciption of the species that observers visiting the right habitat and range likely far from familiar with identification.

  2. Dan Lane says:

    As Simon says, there was a record of several individuals near Trinidad (near Laguna Grande, from what I can tell) by the Schmitts in the 1980s, with a bird netted and collected (LSU) and two recordings (published on the ARA-Records Thrush cassette). Then, there are two specimens at the Museo de Noel Kempff Mercado from November 1993, one from Santa Rosa, the other from San Bernardo. The publication of White et al. 1995 (BBOC 115:29-33) covers a few more records that are from the 80s and early 90s (although I can find no evidence to support the report that Ted Parker encountered the species at PN Noel Kempff Mercado… which seems an odd site to begin with).

    After searching for the species for several years in Beni, I finally encountered it last year (see recordings here: ). This bird was in gallery forest along the Mamore well north of Trinidad. We only encountered one and it was not interacting with other thrushes around (I have also encountered T. hauxwelli and T. amaurochalinus at this site). Probably, the species keeps a low profile during the dry season (when not singing), and may be more common than reports indicate, but this is simply an assumption on my part. Additional searches (probably best to use playback) in gallery forest will be a good way to see if the species is more common and widespread. But with present knowledge, I think the conclusion that we must keep it ‘Data Deficient’ is the best course.

    Three LSU students are just returning from the Beni as I write this (Jan 2011), and they successfully encountered the species just now, so perhaps they will have additional useful comments to make about the species.

  3. Dan Lane says:

    Sorry, the recordings I made in Beni are on Xeno-canto (seems the link didn’t come through).

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