Archived 2019 topic: Ringed Storm-petrel (Hydrobates hornbyi): request for information.

BirdLife species factsheet for Ringed Storm-petrel

The Ringed Storm-petrel (Hydrobates hornbyi) has been observed in thousands in the eastern Pacific Ocean, from 0°S to 35°S along the coast of Ecuador, Peru and Chile (Spear and Ainley 2007, Onley and Scofield 2007). Brooke (2004) suspected the global population to number at least thousands of individuals, and probably tens of thousands, and marine surveys in the 1980s-1990s led to an estimated abundance of 637,200 in spring (95% CI: 0.5-0.8 million) and 1,011,900 in autumn (95% CI: 900,000-1,500,000) (Spear and Ainley 2007).

The species’s breeding sites are poorly-known. The species has been considered likely to breed in the coastal desert of southern Peru and northern Chile (Brooke 2004, Carboneras et al. 2019), and the species’s at-sea distribution and observations of grounded birds have indicated that it nests between 20° and 25°S in Chile and in Peru (Murillo et al. 2013). Since no large colonies have been found, it has been speculated that the species breeds in ‘small, scattered groups’ (Brooke 2004). Individuals have been reported inland at Caraz, Peru, c. 100 km from the coast and at an altitude of 2,250 m (Gardner 1986 in Brooke 2004) and in the Peruvian Andes from Huaraz to Arequipa, at altitudes of 2,300-3,400 m (Murillo et al. 2013). Adults and fledglings attracted to lights have been recorded in localities in desert areas across a broad area of southern Peru (Huarmey, Lima, Lunahuana, Arequipa, Moquegua, Ite and Tacna [Koepcke 1964, Drucker and Jaramillo 2013, Murillo et al. 2013, eBird 2017, Barros et al. 2018]) and northern Chile (Arica, Iquique, Tocopilla, Michilla, Mejillones, Antofagasta, Baquedano, Sierra Gorda and La Negra [Brooke 2000, Brooke 2004, Gómez 2012, eBird 2017, Barros et al. 2018]).

However, no breeding birds had been recorded until a series of surveys was carried out along 780 linear kilometres of the Atacama Desert in northern Chile between 2013-2017. The surveys discovered 25 cavities with signs of storm-petrel breeding activity in the area of Pampa de Indio Muerto, 20 km north of the city of Diego de Almagro, and later captured one H. hornbyi individual at a site 75 km from the coast and at 1100 m above sea level (Barros et al. 2018). The breeding cavities were located in outcrops of gypsum in an area of pampa, and the authors noted that the breeding area could be much larger than that discovered, based on the large area of similar habitat that was not surveyed (Barros et al. 2018).

The species is thought to be threatened by light pollution, which disorientates juveniles, potentially leading to death (Murillo et al. 2013).  Dozens of juveniles of this species were recovered in Lima city between 2009 and 2012 (Murillo et al. 2013). Light pollution has been shown to pose a threat to closely-related species when a high enough proportion of the total population has been affected (Rodriguez et al. 2017). Mining and the development of solar energy, roads and power lines may threaten the species’s breeding sites in the Atacama desert (Barros et al. 2018, 2019).

H. hornbyi is currently listed as Data Deficient. Now that more information has been obtained on the species, we are undertaking a full review of the species’s Red List status. Our current information on the species’s conservation status will now be compared to all Red List Criteria.

Criterion A – We have no data on population trends. The species may be declining as a result of threats, including light pollution, but since we have no data from which to quantify population trends, the species cannot be correctly assessed against Criterion A.

Criterion B – The species has a large at-sea range and its Extent of Occurrence (EOO) is estimated at c. 2,761,700 km2. This does not approach the threshold for listing the species as threatened under Criterion B1. The species is therefore assessed as Least Concern under this criterion.

The species’s Area of Occupancy (AOO) has not been quantified. To date, only one breeding colony has been located, and the area of this colony may have a very small area that would fall beneath the thresholds for threatened categories under Criterion B2. However, this species’s population has been estimated to number in the thousands and probably tens of thousands (Brooke 2004), with abundance at sea in spring estimated at 0.5-0.8 million individuals (Spear and Ainley 2007). Based on this range of population estimates, the species can be inferred to breed over a larger area than that of the breeding colonies discovered so far. Furthermore, since a large colony would likely have been detected, it has been supposed that the species may breed in ‘small, scattered groups’ (Brooke 2004).

Surveys of the closely-related Markham’s Petrel H. markhami, which breeds in a similar habitat in the Atacama Desert, found colonies with densities of between 2.2 and 248.15 pairs per hectare, with a mean density of 182 pairs per hectare (Barros et al. 2019). Based on the abundance estimates of Spear and Ainley (2007) and assuming the abundance in spring to represent mature individuals and that all mature individuals are breeding, the area of breeding colonies can be tentatively calculated at between 10 km2 and 1,800 km2.

Whilst it is not in fact likely that all mature individuals are breeding, AOO figures should be calculated at a scale of 4 km4 grid cells, so rescaling the area of breeding colonies to the required scale would likely inflate the figures given above. If we assume that the species has ‘small, scattered colonies’, each of which must contribute at least 4 km2 to the species’s AOO, then we can conclude that the AOO is unlikely to fall beneath 10 km2. From these extremely preliminary figures, the species’s AOO is assessed as falling within a range that may qualify the species as Vulnerable, Near Threatened or Least Concern under Criterion B2. Yet, to list the species as threatened on the Red List under Criterion B, two of conditions a-c must also be met.

Storm-petrels are highly mobile and the species’s population is not likely to be severely fragmented. The number of locations is difficult to quantify because it is determined by the ‘geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present’. If we assume that the species has ‘small, scattered colonies’ and that none of these are likely to be impacted by the same threats, then the species would likely have more than ten locations. However, if the colonies are concentrated in one or several geographic areas, in which a threat such as light pollution from a city could potentially affect a high proportion of breeding individuals, then the number of locations could be lower.

We have no quantified data from which to estimate, infer or project a continuing decline. Individuals are known to be affected by light pollution (Murillo et al. 2013), which has impacted on other closely-related species (Rodriguez et al. 2017), so we could suspect that this threat is causing a decline in mature individuals in this species. Additionally, the breeding colonies may be affected by mining and development (M. Ramirez in litt. 2019). If there is further evidence to indicate an ongoing decline in the area or extent of the species’s breeding habitat, than condition b may be met. If not, then declines are only suspected and condition b is not met. There is no evidence that the species’s population or range size are undergoing extreme fluctuations. Condition c is not met.

Based on current evidence, the species may qualify as Near Threatened as it potentially meets the area threshold for listing as Vulnerable under Criterion B2, but it is unclear whether condition a is met and a continuing decline is currently only suspected. Should further information indicate that the species has fewer than ten locations, and allow us to observe, estimate, infer or project a continuing decline, the species could qualify for listing as Vulnerable under Criterion B2ab. Conversely, if we conclude that the species is likely to have significantly more than ten locations, then the species may be assessed as Least Concern under Criterion B.

Criterion C – Marine surveys in the 1980s-1990s led to an estimated abundance of 637,200 in Spring (95% CI: 0.5-0.8 million) and 1,011,900 in autumn (95% CI: 900,000-1,500,000) (Spear and Ainley 2007). Assuming the lower population estimates in spring represent mature individuals, we can derive from these surveys a population estimate of 500,000-800,000 mature individuals. These figures do not meet or approach the threshold for listing the species as threatened under Criterion C. The species is assessed as Least Concern under this Criterion.

Criterion D – The population estimate of 500,000-800,000 mature individuals does not meet or approach the population threshold for listing the species as threatened under Criterion D. Although the species may have a highly restricted AOO or number of locations, the species’s is likely to breed in ‘small, scattered groups’ (Brooke 2004), so it is unlikely that there is a plausible future threat that could drive the species to Critically Endangered or Extinct within one generation (16 years). Therefore, the species is assessed as Least Concern under Criterion D.

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:

  • the size of the area occupied by the species’s breeding colonies.
  • trends in the species’s population and in the area and quality of its habitat.
  • threats affecting the species and its habitat, and the areas and rates of impact of these threats.

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

Barros R., F Medrano, R. Silva & F. de Groote. (2018) First Breeding site record of Hornby’s Storm Petrel Oceanodroma hornbyi in the Atacama Desert, Chile. Ardea 106(2): 203-207.

Brooke M. (2000) Report on a project supported by a BOU research grant. Ibis 142: 348–349.

Brooke, M. de L. (2004) Albatrosses and Petrels Across the World. Oxford University Press, Oxford.

Carboneras, C., Jutglar, F., Kirwan, G.M. & Sharpe, C.J. (2019) Ringed Storm-petrel (Hydrobates hornbyi). 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/52601 on 9 May 2019).

Drucker J. & Jaramillo A. (2013) Ringed Storm-Petrel (Oceanodroma hornbyi), version 1.0. In: Schulenberg T.S. (ed.) Neotropical birds online. Cornell Lab of Ornithology, Ithaca, NY, USA.

Gómez G. (2012) Relación entre la presencia de la golondrina de mar de collar, Oceanodroma hornbyi (Procellariiformes; Hydrobatidae), iluminación artificial y fase lunar, en el norte de Chile, región de Antofagasta. Undergraduate thesis, Universidad de Antofagasta, Antofagasta.

Koepcke M. (1964) Las aves del departamento de Lima. Gráfica Morsom, Lima, Perú.

Murillo Y, Piana RP & Delgado-Alburqueque L. (2013) Rescate de Golondrinas de la Tempestad de Collar (Oceanodroma hornbyi) en la ciudad de Lima, Perú. Boletín de Ornitología Peruana-UNOP 8: 55-64.

Onley, D. & Scofield, P. (2007) Field guide to the albatrosses, petrels and shearwaters of the world. Christopher Helm, London.

Rodríguez, A., Holmes, N.D., Ryan, P.G., Wilson, K., Faulquier, L., Murillo, Y., Raine, A.F., Penniman, J.F., Neves, V., Rodríguez, B., Negro, J.J., Chiaradia, A., Dann, P., Anderson, T., Metzger, B., Shirai, M., Deppe, L., Wheeler, J., Hodum, P., Gouveia, C., Carmo, V., Carreira, G.P., Delgado‐Alburqueque, L., Guerra‐Correa, C., Couzi, F., Travers, M. & Corre, M. L. (2017) Seabird mortality induced by land‐based artificial lights. Conservation Biology 31: 986-1001. Spear, L. B. & Ainley, D. G. (2007) Storm-petrels of the eastern Pacific Ocean: species assembly and diversity along marine habitat gradients. American Ornithologists’ Union, Washington, DC.

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3 Responses to Archived 2019 topic: Ringed Storm-petrel (Hydrobates hornbyi): request for information.

  1. The following comments were made by a team of the NGO “Red de Observadores de Aves y Vida Silvestre de Chile”, who have been working in natural history and conservation of this species since 2013.

    We agree that the species doesn’t reach the threshold for being threatened under the criteria “C”, and there is not enough information for the criteria “A” “B”, “D” and “E” (so, probably should be reclassified as “Data Deficient” again).

    On the other hand, some information could be suspected/inferred:

    Criteria “B”: The only known colony has 12.91 km2 (Medrano et al. 2019). It’s highly probable that there are not 154 colonies of that size (which would be necessary for reaching the threshold of 2000 km2 of breeding AOO for “Vulnerable”). For using the Criteria B, two other conditions must be met:

    – Probably the population is not severely fragmented
    – The number of known breeding locations is one (Barros et al. 2018), with two other places where just one nest was discovered (probably they can’t be considered as a “location” sensu stricto). As you said, there are probably several “ ‘small, scattered groups’ (Brooke 2004).”, but there is a high uncertainty about if the number of localities reaches the threshold number of 10 localities.
    – The habitat quality is being degraded, since an optimal habitat it is a desert free of light pollution, which affects several hundreds of individuals each year (Silva et al. in prep).

    Probably, under this criteria should be classified as “Data Deficient”, because the uncertainty on the locations number, although a more conservative criteria would be to consider there are less than 10 locations in which case the species would reach the criteria B2ab(iii) for “Vulnerable”.

    Criteria “D”: As was exposed above, probably, under this criteria should be classified as “Data Deficient”, because the uncertainty on the locations number.

    In this case, under the uncertainty on the number of locations (which could be the factor for classifying the species as Vulnerable under the criteria B2ab(iii)D2), and the spatial uncertainty (most of the knowledge comes just from one colony, despite its wide range), we suggest that the species is reclassified as “Data Deficient” until more information.

    Thanks in advance and looking forward for your reply,
    Red de Observadores de Aves y Vida Silvestre de Chile.

  2. Hannah Wheatley (BirdLife) says:

    Preliminary proposal

    Based on available information, our preliminary proposal for the 2019 Red List would be to list Ringed Storm-petrel (Hydrobates hornbyi) as Near Threatened as it approaches the thresholds for listing as threatened under Criterion B2.

    There is now a period for further comments until the final deadline in mid-July, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from those in the initial proposal.

    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.

  3. Hannah Wheatley (BirdLife) says:

    Thank you very much for the helpful comment and additional information, which unfortunately was missed in error prior to the preliminary decision being posted. We are very grateful for your contributions and we have now reviewed the additional information, including the recent paper cited above, Medrano et. al. 2019.

    According to Medrano et. al. 2019, the surveyed colony at la Pampa del Indio Muerto has a total area of 129.1 km2 and a mean density of 0.61 pairs per hectare – equivalent to 61 pairs per km2, or 122 mature individuals per km2. Based on this density, the species would need to have a population smaller than 244,000 mature individuals to have a total colony area smaller than 2,000 km2; or fewer than c.15 colonies of the same size as that recorded.

    Although the species’s population size is currently listed as 1,000-90,000 individuals, this was a suspected population size based on expert judgement. Marine surveys in the 1980s-1990s led to an estimated abundance of 637,200 in spring (95% CI: 0.5-0.8 million) and 1,011,900 in autumn (95% CI: 900,000-1,500,000) (Spear and Ainley 2007). The results of Medrano et. al. indicated that around 16,000 mature individuals occupy one colony alone. The species is thought likely to breed in ‘small, scattered groups’ (Brooke 2004) and individuals have been recorded inland across a wide latitudinal range. Given that the population size beneath which the species would be estimated to have a total colony area of <2,000 km2 is less than half of the population size estimated by Spear and Ainley 2007, we consider that it is unlikely that the species has an Area of Occupancy (AOO) that falls beneath the threshold for listing the species as Vulnerable under Criterion B2.

    Furthermore, to list the species as threatened under Criterion B, two conditions would need to be met. Since the species is not considered to be undergoing extreme fluctuations (condition c), the species would need to meet both condition a (severely fragmented or 10 or fewer locations), and condition b (continuing decline).

    The species is not considered to be severely fragmented. According to the IUCN definition, a location does not necessarily equate to one breeding locality. A location is defined as follows: “a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat.” (IUCN 2001, 2012b). The main threats to this species are considered to be light pollution and solar energy developments (Medrano et. al. 2019). We consider it unlikely that light pollution could cause the entire colony at la Pampa del Indio Muerto to be eliminated in the period of one generation; neither would a single solar energy development be likely to destroy the entire colony. Therefore, the colony at la Pampa del Indio Muerto probably represents multiple locations. Taking into account the population estimates described above, and that the species is likely to breed in ‘small, scattered groups’ (Brooke 2004), we consider it likely that the species has more than ten locations in total, and hence condition a is not met.

    It is possible that there is a continuing decline in the quality of habitat due to an increase in light pollution, so condition b could be met.

    If only one of the three conditions a-c is met, we are unable to list the species as threatened under Criterion B. However, given the uncertainty around the total population size, and hence the species’s AOO, we propose to list the species as Near Threatened as it approaches the thresholds for listing as threatened under Criterion B2ab(iii).

    The IUCN Red List Guidelines contain the following guidance on when it is appropriate to list a species as Data Deficient (DD): “if the data are so uncertain that both CR and LC are plausible categories, the taxon can be listed as DD. If, however, plausible categories range from NT to threatened categories, DD is not the appropriate category. In this case, the assessor must select the most plausible category.”

    Based on current information, there is no evidence to suggest that this species could come close to qualifying for listing as Critically Endangered (CR). Therefore, it would not be appropriate to continue to list the species as Data Deficient.

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