Justification of Red List Category
Although this species is not well known, surveys at sea and at one breeding colony suggest that its population size and range are above the thresholds for listing the species as threatened under Criteria B, C or D and we have no evidence to suggest that it is declining at a rate that would approach the threshold for threatened under Criterion A. However, the area of its breeding colonies is small and highly uncertain and the species may be declining as a result of light pollution. For these reasons, the species is listed as Near Threatened.
Brooke (2004) suspected the global population to number at least thousands of individuals, and probably tens of thousands. 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. The subpopulation structure is not known.
The species may be declining as a result of threats, including light pollution, but we have no data from which to quantify population trends.
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). The species’s breeding sites are poorly-known. It 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]). Between 2013 and 2017, surveys along 780 linear kilometres of the Atacama Desert in northern Chile discovered 25 cavities with signs of storm-petrel breeding activity in the area of Pampa de Indio Muerto in southern Antofagasta, Chile, and later captured one individual at a site 75 km from the coast and at 1,100 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). Further surveys of the same breeding colony in 2018 estimated a population of 7,919 pairs in an area of 129.1 km2 (Medrano et al. 2019). The authors also discovered a single nest cavity at Salar de Quiuña in the region of Tarapacá, northern Chile, and observed an individual leaving a cavity in gypsum at Salar de Navidad, central Antofagasta, Chile (Medrano et al. 2019). In 2018, a colony of several abandoned nests, one of which contained a dead H. hornbyi individual, were found at a a site in the Loa gorge, Tarapacá (Malinarich Torrico et al. 2018). 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).
It nests inland in the arid areas of northern Chile and probably Peru. Eggs are laid in December-January, with chicks found in the nests from February-June (Medrano et al. 2019). Nest cavities have been recorded inland at 1,085-1,100 m above sea level in cavities in gypsum outcrops and in a salt cavity (Barros et al. 2018, Medrano et al. 2019). It feeds mainly on the wing, by pattering, dipping and snatching from surface (Carboneras et al. 2019). It is pelagic and has been recorded far from the coast (Carboneras et al. 2019).
The species is thought to be threatened by light pollution, which disorientates juveniles, potentially leading to death (Murillo et al. 2013, Rodriguez et al. 2017). 69 grounded individuals were rescued in Tarapacá between 2010 and 2017, mainly during June-September (Malinarich Torrico 2017). Rescue workers have recorded 160 birds per year grounded due to light pollution in Antofagasta and 77 per year in Lima (Rodriguez et al. 2017). 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).
Conservation Actions Underway
The Ringed Storm-petrel Project recovers fledglings which have landed and are likely disoriented by the light pollution in urban areas along the cost in Lima, Peru. The 'Storm-petrels of the desert' (Golondrinas del desierto) project has been searching for breeding colonies and surveying breeding individuals (ROC 2018). The project also aims to implement protection of breeding colonies, reduce light pollution, evaluate the impact of mining, solar energy, power lines and road development and develop a species action plan (ROC 2018).
Conservation Actions Proposed
Search for more breeding colonies on offshore islands, coastal cliffs and the arid hinterland of the Antofagasta region in March-July, looking for burrows and signs of nesting, listening for night-time flight calls and following up reports of dead or grounded fledglings inland (Schmitt et al. 2016). Monitor population trends at breeding colonies and at sea. Study the routes used between nesting colonies and the sea (Medrano et al. 2019). Research the areas used at sea and the marine threats. Research the impact of light pollution; reduce and mitigate the consequences of this threat. Further improve fledgling rescue operations and carry out citizen education campaigns in Peru and Chile. Protect known breeding colonies and flight paths between colonies and the sea (Medrano et al. 2019).
Text account compilers
Martin, R., Sharpe, C.J., Miller, E., Moreno, R., Stuart, A., Fjagesund, T., Benstead, P., Wheatley, H., Hermes, C., Symes, A., Isherwood, I.
Cancino, L., Gaskin, C., Murillo, Y., Silva, R. & Vanerio Ramirez, M.
BirdLife International (2020) Species factsheet: Hydrobates hornbyi. Downloaded from http://www.birdlife.org on 19/02/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/02/2020.