Archived 2010-2011 topics: Black-backed Thornbill (Ramphomicron dorsale) and Santa Marta Wren (Troglodytes monticola): uplist both to Endangered?

Black-backed Thornbill Ramphomicron dorsale is endemic to the Santa Marta Mountains of Colombia, where it occurs from 2,000-4,600 m.  It is currently classified as Least Concern but its Extent of Occurrence has recently been estimated at 2,600 km2.

Santa Marta Wren Troglodytes monticola is another Santa Marta endemic, found in low, thick shrubbery at the timberline and in sheltered spots high in the páramo zone, from 3,200 to 4,600 m. It is known from collections made in 1922 and from one record in the upper río Frío Valley, at 3,600 m, where a pair was observed and tape-recorded in a small montane forest patch (c.2 ha) amidst heavily burned and overgrazed páramo. It is currently classified as Vulnerable on the IUCN Red List, however its Extent of Occurrence has recently been estimated at 1,300 km2.

Loss of páramo vegetation in the Santa Marta Mountains has been acute – páramo is regularly burned and streamside vegetation is unsustainably cut for firewood (N. Krabbe in litt.).

Both species may now qualify as Endangered under criterion B1a+b if their range is now severely fragmented (having an Extent of Occurrence <5,000 km2 and a continuing decline in at least the Area of Occupancy, area, extent and/or quality of habitat and number of locations or subpopulations, and number of mature individuals).

Comments on this proposal and the status of these species, particularly focusing on the degree of fragmentation, number of locations, and rate of habitat loss, are sought.

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4 Responses to Archived 2010-2011 topics: Black-backed Thornbill (Ramphomicron dorsale) and Santa Marta Wren (Troglodytes monticola): uplist both to Endangered?

  1. I have seen Ramphomicron dorsale and Troglodytes monticola at Cuchilla de San Lorenzo (Santa Marta). More needs to be known about habitat use and the natural history of these species. However, deforestation (for agriculture) is severely affecting the core of their ranges in the Sierra de Santa Marta, where deforestation has reached the 2,000-4,600 m area vital for these birds. This worrying news suggests that the species now warrant uplisting to Endangered owing to their very small ranges and declines in the extent and quality of habitat in the Sierra de Santa Marta Sierra.

  2. Troglodytes monticola has previously never been seen, heard or collected on Cuchilla de San Lorenzo despite the area having received extensive ornithological attention for ~100 years, especially in the past ten years by hundreds of bird watchers. Given this, it would be good if Oswaldo Cortes could confirm any evidence of his record as it would be an extremely significant.

  3. Andy Symes says:

    Fundacion ProAves have provided the following information on Santa Marta Wren:

    BioMap reports 39 specimens of Troglodytes monticola, all but five taken by Carriker in 1946 from locations on the northern and southeastern slope of Santa Marta: Mamancanáca (20), Rio Guatapuri (10); Páramo de Macotama (2) and Páramo de Chirigua (7). There have been no specimens since 1946 (www.BioMap.net). Todd & Carriker (1922) considered the species to be “confined to the Paramo Zone of the Sierra Nevada de Santa Marta, having been discovered by Mr. Brown on the Paramos de Chiruqua and Macotama, at elevations ranging from 11,000 to 15,000 feet [3350-4570 meters], although it has not been detected below the latter altitude by the present writer. It is found in the low, thick shrubs and bushes in the more sheltered parts of the páramo. It is a very shy bird, rarely coming out into the open, and being silent is easily overlooked.”

    The only records since 1946 are from Strewe & Navarro (2004) in the upper río Frío Valley at 3,600 m, “where a pair was observed and tape-recorded in a small montane forest patch (c.2 ha) amidst heavily burned and overgrazed páramo. Only one other such intact forest patch was found in an area of c.5,000 ha, some 12 km distant, where we unsuccessfully searched for the species. The wren’s habitat is extremely isolated, due to burning and overgrazing. Thus, based on our work in the río Frío Valley, T. monticola appears to be threatened, due to its very narrow distribution, low population density and habitat destruction.”.

    Searches on the southern slopes (historical location) by ProAves / Niels Krabbe failed to located the species in 2007. Further attempts to locate the species on the most intact western slopes are being pursued by ProAves. The species has never been found in El Dorado Bird Reserve along the Cuchilla de San Lorenzo, which includes elevations of up to 2,700 m elevation. We suspect this species is restricted to the narrow ecotone of timberline vegetation rather than a páramo specialist, which would greatly narrow the EOO and AOO to also place it as CRB1a+2. Unlike some other Troglodytes in the Americas, this species appears to have particular, undisturbed habitat requirements. The apparently related and more widely distributed Mountain Wren T. solstitialis is found largely in forest and forest borders, rather than open habitats in the upper montane forest zone (around 2400-3500 m in Colombia). With the present and growing pressures on the upper montane forest, timberline and páramo as a principal zone of grazing and deforestation (from burning) by local people, we see that T. monticola’s population has undergone a severe (suspected >70% during the past 10 years) decline that will accelerate. Notably, no known viable populations exist for this species today.

    The southeastern slope has been most devastated at relevant elevations, being more heavily burnt and with greater human population at higher elevations than elsewhere in the Sierra Nevada. However, as Strewe & Navarro (2004) report, this species is even under severe threat on the northern slope. Based on current limited information, severe habitat loss, and suspected population reduction in the past and future decade, we recommend this species be treated as CRITICALLY ENDANGERED meeting criteria: B1a+2, C2a, D.

    A further priority for this species would be to assess its status as a species or subspecies of T. solstitialis, a matter which has not been subject to detailed vocal analysis owing to the lack of sound recordings and other field data.

    Todd, W. E. & Carriker, M. A. 1922. The birds of the Santa Marta region of Colombia: a study in altitudinal distribution. Ann. Carnegie Mus., vol. 14.

    Strewe, R. & Navarro, C. 2004. The threatened birds of the río Frío Valley, Sierra Nevada de Santa Marta. Cotinga 22: 47-55.

    Fundacion ProAves (in press) The status of various threatened or potentially threatened birds in Colombia. Conservación Colombiana 14

  4. Andy Symes says:

    Fundacion ProAves have provided the following information on Black-backed Thornbill:

    Each year, there are several seasonal records of Ramphomicron dorsale from January to early June and August in Fundación ProAves’ 1,900 acre El Dorado Bird reserve in the Santa Marta mountains. Mist-netting each month for 2-3 days from 2004 to 2008 at this site has resulted in captures of only six individuals (always immature males or females). Since 2010, 1-2 females started feeding from hummingbird feeders at the EcoLodge of the reserve at 1,900 m elevation. However, no male has ever been seen or photographed and we cannot confirm if there have been records of this species recently at any other location in Santa Marta. The species is known from ten specimens (www.BioMap.net), nine of which are of unknown date (probably 1800’s) and one specimen from 1972 from “Cuchilla de San Lorenzo” (modern day site of El Dorado Bird Reserve) by J. Munves. Carriker did not find or collect this species despite decades of work in the area and was perplexed as to the species’ movements and habitat. It seems likely that the species breeds in the timberline- páramo ecotone with immature birds observed at lower elevations being wandering individuals. Related R. microrhynchus is similarly largely a paramo / subparamo species.

    Unfortunately, the state of páramo and páramo timberline ecotone in the Sierra Nevada is disastrous – ProAves supported Niels Krabbe to investigate the páramo to search for this and Santa Marta Wren. He reported one of the poorest (impoverished and damaged) páramos he had visited in the Andes, almost devoid of birds. Extensive burning and heavy grazing by indigenous human populations along that sensitive timberline zone (the highest paramos being too inhospitable for grazing animals) combined with the Sierra Nevada’s fragile climate (wide fluctuations and climate change – heavy glacier and snow line meltback) places this species in a precarious position. Based on the few seasonal records of birds from El Dorado Bird Reserve and the state of páramos in the region, we recommend this species be treated as CRITICALLY ENDANGERED meeting criteria: B1a+2, C2a, D.

    Fundacion ProAves (in press) The status of various threatened or potentially threatened birds in Colombia. Conservación Colombiana 14

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