Chestnut-bellied Hummingbird (Amazilia castaneiventris): request for information

BirdLife species factsheet for Chestnut-bellied Hummingbird

Chestnut-bellied Hummingbird (Amazilia castaneiventris) is restricted to the Serranía de San Lucas and the drier parts of the Magdalena Valley, Colombia, with a core range in the Chicamocha, Suarez and Chucuri valleys. It inhabits bushy canyons and edges of lower montane humid forest (Weller et al. 2019). Although there are various sites where the species is now known to be found, it is somewhat unpredictable in occurrence and, at least in the Yariguíes area, not locally abundant. The species is often inexplicably rare in apparently suitable habitats and may go unrecorded for periods (J. Zuluaga in litt. 2009); elsewhere it appears to be resident. The increase in records of the species owes much to increased observer effort, but also may reflect nomadic movements in recent years linked to flowering events on which the species relies to some degree (J. Cortes in litt. 2009). The global population has previously been roughly estimated at 600-1,700 mature individuals.

The species is currently listed as Endangered under Criterion B1. However, following the application of the recommended methodology for estimating extent of occurrence (EOO) using a minimum convex polygon, the revised EOO no longer meets the threshold for listing the species as Endangered under this criterion. Hence, we are undertaking a review of the species’s Red List Category.

Our current information on the species’s conservation status will now be compared to all Red List Criteria.

Criterion A – We have no direct data on population trends. A recent analysis of forest loss data from 2000-2012 indicated that forest was lost within the species’s range at a rate equivalent to 1% across three generations (10.2 years; Tracewski et al. 2016). However, this species inhabits forest edges and shrubland, so forest loss may not be a reliable indicator of population change. An analysis of population size estimated based on modelled densities and remote-sensed land cover data estimated that the species’s population has slightly increased over three generations (Santini et al. 2019). The national Red List of Colombia also estimated an increase in available habitat between 2001 and 2011 (Renjifo et al. 2016). There is no evidence that indicates a past or future population size reduction approaching 30%, so the species is assessed as Least Concern under this criterion.

Criterion B – The species’s extent of occurrence (EOO) is estimated at 11,500km2. This meets the threshold for Vulnerable under Criterion B1. The species’s area of occupancy (AOO) has not been quantified, but based on a 4km2 grid placed over the area of mapped range, must be smaller than 5,452km2. This does not approach the threshold for listing the species as threatened under Criterion B2. To list the species as threatened on the Red List under Criterion B, two of conditions a-c must also be met.

The species is not severely fragmented. The main threat to the species is considered to be habitat loss due to agriculture. According to analyses of remote-sensed data on forest loss and land cover (Tracewski et al. 2016), habitat loss appears to be progressing at a slow rate within the species’s range, or the amount of available habitat may be slightly increasing (Santini et al. 2019). The number of locations (according to the IUCN definition) is therefore likely to be significantly greater than 10. Therefore, condition a is not met. If there is information to indicate a greater rate of habitat loss, the number of locations could be revised.

It is unclear whether there is a continuing decline in the species’s EOO, AOO, extent or quality of habitat, number of locations or subpopulations or number of mature individuals. A recent analysis of forest loss data from 2000-2012 indicated that forest was lost within the species’s range at a rate equivalent to 1% across three generations (Tracewski et al. 2016). However, this species inhabits forest edges and shrubland, so forest loss may not be a reliable indicator of population change or habitat quality for this species. An analysis of area of habitat and population size based on modelled population densities and remote-sensed land cover data estimated that the species’s area of habitat and population has slightly increased over three generations (Santini et al. 2019). The national Red List of Colombia also estimated an increase in available habitat between 2001 and 2011 (Renjifo et al. 2016). Nevertheless, there may be some habitat degradation, for example from logging, and the population may be impacted by hunting as well as habitat degradation (Renjifo et al. 2016). Therefore, condition b may be met, but further information would allow a better assessment.

There is no evidence that the species’s population or range size are undergoing extreme fluctuations. Condition c is not met.

The species’s EOO falls beneath the thresholds for listing the species as Vulnerable, but it is not clear whether conditions a and b are met. If further evidence indicates that the species has ten or fewer locations and is undergoing a continuing decline (for example in its extent or quality of habitat, and/or in population size), then the species may be listed as Vulnerable under Criterion B1. If not, the species may qualify as Near Threatened or Least Concern under this criterion.

Criterion C – The species’s population size was previously estimated at 600-1,700 mature individuals.Based on the area of the species’s mapped range (4,949km2), a range of recorded population densities (10, 33, 60, 140 and 210 individuals/km2; D. C. Sabogal in litt. 2009, Peñuela and Archila 2010, Cortes-Herrera 2006, Renjifo et al. 2016), and assuming that 11-22% of the range is occupied, the species’s population size is estimated to fall within the range 18,600 – 66,300 individuals, roughly equivalent to 12,400 – 44,200 mature individuals. The national Red List of Colombia estimated the population size at 24,120 individuals (Renjifo et al. 2016), roughly equivalent to 16,080 mature individuals. A recent analysis based on land cover data and a population density model estimated the population size at 117,733 mature individuals (Santini et al. 2019).This broad range of population estimates could qualify the species for listing as Endangered, Vulnerable, Near Threatened or Least Concern under Criterion C, depending on where the true population size is most likely to fall.To list the species as threatened on the Red List under Criterion C further conditions must also be met.

It is unclear whether there is a continuing decline in the species’s population size. A recent analysis of forest loss data from 2000-2012 indicated that forest was lost within the species’s range at a rate equivalent to 1% across three generations (Tracewski et al. 2016). However, this species inhabits forest edges and shrubland, so forest loss may not be a reliable indicator of population change. An analysis of area of habitat and population size based on modelled population densities and remote-sensed land cover data estimated that the species’s population size has slightly increased over three generations (Santini et al. 2019). The national Red List of Colombia also estimated an increase in available habitat between 2001 and 2011 (Renjifo et al. 2016). Nevertheless, there may be some habitat degradation, for example from logging, and the population may be impacted by hunting as well as habitat degradation (Renjifo et al. 2016).

We do not have population data from which to estimate the rate of any decline, so the species cannot be assessed under Criterion C1.

The species may have two or more subpopulations, since the record in the Serranía de San Lucas (Donegan 2012) is quite distant from the other recent records. Whether the largest subpopulation is likely to have fewer than 1,000 (or 250) mature individuals will depend on the best estimate of the total population size. It is unlikely that 100% of mature individuals are found in one subpopulation, although it may be the case that 95% are in one subpopulation. It is unclear whether subcriteria 2a(i) and/or 2a(ii) are met.

There is no evidence for extreme fluctuations in the number of mature individuals, so subcriterion b is not met.

Based on the information stated above, the species could qualify for listing as Endangered, Vulnerable, Near Threatened or Least Concern under Criterion C2a. The decision on which category to use depends on the best estimate of population size and whether the species can be inferred to be undergoing a continuing decline in its population size.

Criterion D – Based on the population estimates described above, the species’s population size could potentially meet the threshold for listing as Vulnerable under Criterion D, but it is more likely that the species would qualify as Near Threatened or Least Concern, depending on where the species’s true population size is considered most likely to fall.

The species does not have a restricted area of occupancy of number of locations such that deforestation could drive the species to Critically Endangered or Extinct within a very short time. The species does not therefore meet the criteria for listing as Vulnerable under Criterion D2.

Criterion E – To the best of our knowledge no quantitative assessment of the probability of extinction has been conducted for this species, and so it cannot be assessed against this criterion.

To allow us to achieve a clearer assessment of the species’s status, information is requested on this species’s conservation status. We particularly request information on the species’s population size and trends, as well as on threats which may be impacting on this species, including the rate or extent of any habitat loss or degradation that is underway within the species’s range.

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’s Red List status. Therefore, please make sure your comments are about the proposed listing.

An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.

References

Cortes-Herrera, J. O. (2006) Natural history of Chestnut-bellied Hummingbird.

Donegan, T.M. (2012) Range extensions and other notes on the birds and conservation of the Serranía de San Lucas, an isolated mountain range in northern Columbia. Bull. Brit. Ornithol. Club 132(3): 140-161.

Peñuela, G. and Archila, L. (2010) Aspectos del comportamiento del colibrí ventricastaño, Amazilia castaneiventris (aves: Trochilidae), en la Reserva Natural de aves Cucarachero del Chicamocha. Zapatoca, Santander- Colombia. Tesis para optar a titulo de profesional en Biología, Universidad Pedagógica y Tecnológica de Colombia.

Renjifo L.M., Amaya-Villarreal A.M., Burbano-Girón J., Velásquez-Tibatá J. 2016. Libro Rojo de Aves de Colombia. Volumen II: Ecosistemas Abiertos, Secos, Insulares, Acuáticos Continentales, Marinos, Tierras Altas del Darién y Sierra Nevada de Santa Marta y Bosques Húmedos del Centro, Norte Y Oriente del País. Editorial Pontificia Universidad Javeriana and Instituto Alexander von Humboldt, Bogotá, Colombia.

Santini, L., Butchart, S. H. M., Rondinini, C., Benítez‐López, A., Hilbers, J. P., Schipper, A., Cengic, M., Tobias, J. A. and Huijbregts, M. A. J. (2019) Applying habitat and population‐density models to land‐cover time series to inform IUCN red list assessments. Conservation Biology https://doi.org/10.1111/cobi.13279.

Tracewski, Ł.., Butchart, S. H. M., Di Marco, M., Ficetola, G. F., Rondinini, C., Symes, A., Wheatley, H., Beresford, A. E. and Buchanan, G. M. (2016) Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.

Weller, A. A., Boesman, P. and Sharpe, C. J. (2019) Chestnut-bellied Hummingbird (Amazilia castaneiventris). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55493 on 22 February 2019).

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3 Responses to Chestnut-bellied Hummingbird (Amazilia castaneiventris): request for information

  1. Red List Team (BirdLife International) says:

    Preliminary proposal
    Based on available information, our proposal for the 2019 Red List is to pend the decision on this species and keep the discussion open until 2020, while leaving the current Red List category unchanged in the 2019 update.
    Final 2019 Red List categories will be published on the BirdLife and IUCN websites in December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  2. Thomas Donegan says:

    In case of interest: I have only ever seen this species in mature gardens containing many flowering trees (and flowery forest edges but very occasionally). It does not seem to occur inside primary forest, and only in the 1400-1700 m elevational range. To be honest, gardening to such a level as to produce the sorts of habitats that this species likes most is not a very mainstream activity in rural Colombia and most towns are based on a concreted grid type system, where the species does not occur much if at all. A proper assessment of the species’ population size or range would need to exclude both heavily modified habitats and primary habitats, with an assumption that it is rare at lower and higher elevations of its broad range, and an assessment of where flowery borders occur. Estimates based upon transect work along forest edges may over-estimate population sizes, unless the relevant habitat is consistently fragmented. I tend to believe the lower figures among those mentioned in the text.

  3. Hannah Wheatley (BirdLife) says:

    Recommended categorisation to be put forward to IUCN

    Following further review, our proposal for the 2019 Red List for this species has been changed.

    Chestnut-bellied Hummingbird (Amazilia castaneiventris) is now recommended to be listed as Near Threatened, approaching the thresholds for listing as threatened under Criteria B1ab(iii,v)+2ab(iii,v).

    The final 2019 Red List categories will be published on the BirdLife and IUCN websites in December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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