Markham’s Storm-petrel (Hydrobates markhami): request for information.

BirdLife species factsheet for Markham’s Storm-petrel

Markham’s Storm-petrel (Hydrobates markhami) occurs in the tropical zone of the eastern Pacific Ocean. Between July and September, it is found over warm, equatorial waters, while between January and July it moves to cooler waters of the Peru Current and further west (Pyle 1993, Spear and Ainley 2007). It breeds on the Paracas peninsula on the coast of central Peru and in the Atacama Desert of southern Peru and northern Chile (Carboneras 1992, Barros et al. 2019). Markham’s Storm-petrel breeds in dispersed colonies using fissures and holes created by saltpetre deposits for nesting (Tobias et al. 2006, Schmitt et al. 2015, Barros et al. 2019).

Following the recent discovery of several large breeding colonies in the Atacama, the global population was estimated to number c.50,000-60,000 breeding pairs (Schmitt et al. 2015, Barros et al. 2019). This equates to 100,000-120,000 mature individuals, or 150,000-180,000 individuals in total.

The principle threat faced by Markham’s Storm-petrel is the mining of saltpetre from the salt plain on which it nests (Torres-Mura and Lemus 2013, Barros et al. 2019). This has resulted in the loss of considerable amounts of breeding habitat, as it destroys the burrows and crevices in which nests are placed (Schmitt et al. 2015, Barros et al. 2019). Light pollution also represents a significant level of mortality, with 10-20 fresh corpses reported each morning next to a single light close to a breeding colony (Schmitt et al. 2015). It is assumed that fledglings are attracted to the lights of nearby cities during their first flight (Torres-Mura and Lemus 2013, Schmitt et al. 2015). It has been estimated that each year around 20,000 fledglings die because of light pollution, representing 1/3 of the entire cohort (F. Medrano in litt. 2019). Light-pollution was found to be a severe threat to seabirds and Hydrobatidae in particular, which can potentially have a detrimental effect on the overall population size (Rodriguez et al. 2017). Further threats include infrastructure developments (roads, wind farms, power lines) and garbage (Barros et al. 2019).

Markham’s Storm-petrel is currently classified as Data Deficient, as detailed data on population trends have been lacking. Considering the recently obtained information on the breeding colonies and  potential threats, the species may warrant a change in Red List status. Therefore, we present here our reassessment against all criteria for the species.

Criterion A – The population trend of Markham’s Storm-petrel has not been estimated directly. However, it has been suggested that each year, about 20,000 fledglings die after light-induced grounding (Barros et al. 2019). Based on this, we can suspect that the population is in decline. The rate of decline cannot be assessed based on the available information though, as population decline is measured as the decline in mature individuals. Juvenile seabirds generally have a high mortality for various reasons, which is dependent on age, sex and environmental parameters (Fay et al. 2015). It is not clear how many juveniles of Markham’s Storm-petrel die of natural causes each year, or if the reduced population density may even enhance the survival of the remaining fledglings, as has been shown in other seabirds (Fay et al. 2015). As such, it is unclear to which extent the light-induced mortality of juveniles affects the recruitment and the population size of Markham’s Storm-petrels.  

In order to be listed as Vulnerable, Markham’s Storm-petrel would have to undergo a decline of ≥ 30% over three generations. Therefore, information is urgently sought regarding the potential current rate of decline in mature individuals (e.g. within a known colony), to see whether the overall rate of decline in this species is large enough to warrant its listing under Criterion A4e and possibly additionally A3e.

Criterion B – Using a Minimum Convex Polygon, the Extent of Occurrence (EOO) of this species has been calculated as 14 million km2. This is far too large for listing the species as Vulnerable and therefore, Markham’s Storm-petrel may be considered Least Concern under Criterion B1.

The Area of Occupancy (AOO) has not been calculated. Following IUCN Guidelines (IUCN 2001, 2012), the AOO is measured by a 4 km2-grid, to be overlaid over the area of known breeding colonies. We can derive a rough estimate of the AOO based on the population density in the known breeding colonies. For several colonies in Chile, the area has been measured. These include Pampa Chuño (41 ha), Pampa Chaca (6,100 ha) and Pampa Camarones (2,209 ha) in Arica, as well as Pampa La Perdiz (33 ha) (Barros et al. 2019). A large colony in Salar Grande holding c.20,000 pairs has not been measured; however based on the number of breeding pairs we can assume that it covers roughly the same area as the colony in Pampa Chaca (c.6,000 ha). There is no recent information available about the area of the colony in Paracas in Peru; in the 1990s it contained c.2,300-4,600 pairs (Barros et al. 2019). This is about 10-20% of the colony in Pampa Chaca; therefore the colony in Paracas may cover 10-20% of the area of Pampa Chaca, i.e. 600-1,200 ha. Based on this very preliminary estimate, all known colonies may cover c.150-160 km2. Additionally, there are several other colonies in Chile which have not been measured (Barros et al. 2019). Consequently, we can conclude that the AOO of Markham’s Storm-petrel must be larger than 150 km2. This is supported by Barros et al. (2019), who report an AOO of c.250 km2, though no details are given on how this value was derived. We can therefore tentatively assume that the species meets the threshold for listing as Endangered under Criterion B2 (AOO < 500 km2). However, in order to be listed under this criterion, at least two further conditions have to be met.

Based on the size of the breeding colonies, the species cannot be considered severely fragmented sensu IUCN (i.e. most individuals are found in small, isolated subpopulations; IUCN 2001, 2012). The seven known colonies in Chile are subject to a variety of threats, which affect the colonies to a different scale (Barros et al. 2019). The most severe threats to the species are mining, light pollution and infrastructure developments. All these threats represent single events, which are restricted to a very small geographical scale. Per IUCN, a location is defined as a place where one threatening event can quickly eradicate the entire population (IUCN 2001, 2012). Mining only represent a threat to two of the known colonies, both of which extend over 20 and 40 km in length. Each of these colonies therefore most likely consists of a high number of locations. Similarly, light pollution and infrastructural developments, respectively, are affecting only three colonies each, which also contain a high number of locations. Therefore, we can conclude that Markham’s Storm-petrel occurs at > 10 locations and does not meet condition a. In several places throughout the colonies, AOO and habitat quality are observed to be declining due to ongoing mining, garbage pollution and infrastructural development. The species therefore meets conditions b(ii,iii). There is no evidence of a decline in EOO and number of subpopulations and the population decline is only suspected based on a number of fledglings dying each year, and so the species does not meet condition b(i,iv,v). Moreover, there is no evidence of extreme fluctuations, and so condition c is not met.

Overall, even though the species may have a small AOO, it does not meet enough conditions to list it as threatened. On a precautionary basis, it may be considered Near Threatened though, approaching the threshold for listing as threatened under Criterion B2ab(ii,iii).

Criterion C – The population of Markham’s Storm-petrel is estimated to number 100,000-120,000 mature individuals. This is too large to warrant listing the species under Criterion C, and as such, Markham’s Storm-petrel may be considered Least Concern under this criterion.

Criterion D – The population size and range of this species are too large for listing as Vulnerable and therefore, Markham’s Storm-petrel may be considered Least Concern under this criterion.

Criterion E – To the best of our knowledge no quantitative analysis of extinction risk has been conducted for this species. Therefore, it cannot be assessed against this criterion.

Therefore, it appears that the only criteria where the species might meet the threshold for Vulnerable are A4e, and possibly additionally A3e. To better assess the species against these criteria, we urgently request up-to-date information regarding the rate of decline in mature individuals of Markham’s Storm-petrel.

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of its Red List status. Therefore, please make sure your comments are relevant to the discussion outlined in the topic.

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.


Barros, R.; Medrano, F.; Norambuena, H. V.; Peredo, R.; Silva, R.; de Groote, F.; Schmitt, F. 2019. Breeding phenology, distribution and conservation status of Markham’s Storm-petrel Oceanodroma markhami in the Atacama Desert. Ardea 107: 75-84.

Carboneras, C. 1992. Hydrobatidae (Storm-Petrels). In: del Hoyo, J.; Elliott, A.; Sargatal, J. (ed.), Handbook of the birds of the world, pp. 258-271. Lynx Edicions, Barcelona, Spain.

Fay, R.; Weimerskirch, H.; Delord, K.; Barbraud, C. 2015. Population density and climate shape early-life survival and recruitment in a long-lived pelagic seabird. Journal of Animal Ecology 84: 1423-1433.

IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.

IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.

Pyle, P. 1993. A Markham’s Storm-Petrel in the northeastern Pacific. Western Birds 24: 108-110.

Schmitt F., R. Barros & H.V. Norambuena. 2015. Markham’s Storm Petrel breeding colonies discovered in Chile. Neotropical Birding 17: 5-10.

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.

Tobias, J. A.; Butchart, S. H. M.; Collar, N. J. 2006. Lost and found: a gap analysis for the Neotropical avifauna. Neotropical Birding 1: 4-22.

Torres-Mura J. C.; Lemus, M. L. 2013. Breeding of Markham’s Storm-Petrel (Oceanodroma markhami, Aves: Hydrobatidae) in the desert of northern Chile. Revista Chilena de Historia Natural 86: 497-499.

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