Markham's storm petrel

Oceanodroma markhami is a storm petrel of the family Hydrobatidae, described by Salvin in 1883 ^[1]; some recent studies place it in the genus Hydrobates ^[2]. Peru's regulation on threatened species calls it «golondrina de mar de Markham» ^[3], and the Master Plan of the Paracas National Reserve calls it «golondrina de la tempestad» ^[4]. It is a small pelagic seabird that breeds in scattered colonies in the Sechura and Atacama deserts ^[2]. Peru's official list of threatened wildlife places it in the Vulnerable category ^[3].

It is 21 to 23 cm long ^[2]. The plumage is dark almost throughout, with a conspicuous diagonal band across the upper side of each wing, and the tail is forked ^[5]. A newly fledged female found in 2023 weighed 32.7 g, was 200 mm long with a wingspan of 483 mm, and had a black bill, tarsi and toes ^[5].

The 2 chicks found in nests in Tacna, more than 60 days old, were identified by their plumage: primaries and tail feathers already black, remaining greyish down on the flanks, belly and back, and new feathers of a uniform black on the forehead, crown, throat and ear coverts ^[6].

Similar species

• Oceanodroma melania: Very similar, but its pale bars on the upper side of the wing reach as far as the wrist ^[5]. It ranges from Panama to at least 8° S, so off northern Peru the two species can be confused at sea ^[7].
• Oceanodroma hornbyi: It shows much white and grey on the head and body; in Oceanodroma markhami, by contrast, even the new head feathers of chicks are entirely black ^[6].
• Oceanites gracilis: It shows the white rump that Oceanodroma markhami lacks, and the latter also has a longer, sturdier bill ^[6].
• Oceanodroma tethys: It also has a white rump, absent in Oceanodroma markhami, whose bill is longer and sturdier ^[6].

It occurs mainly over tropical waters of the eastern Pacific, between 5° N and 29.9° S ^[2]. During the 3 pelagic resource assessment cruises run by IMARPE in 2019 it was seen off the whole Peruvian coast, with most sightings beyond the continental shelf; the mean distance from shore was 56.1 nautical miles in summer, 40.3 in autumn and 56.9 in spring ^[7].

Its concentrations shifted with the season: in summer it gathered between Chimbote and Pisco, in autumn between Atico and the Chilean border, and in spring in two cores, one between Tumbes and Puerto Chicama and another between Punta Caballas and the border with Chile ^[7]. It used cold coastal waters, subtropical surface waters and the mixture of the two ^[7].

To breed it moves inland into the Sechura and Atacama deserts, where it uses fissures and cavities below the surface of salt flats ^[2]. In Peru, breeding areas were known on the Paracas Peninsula and on La Vieja and San Gallán islands, inside the Paracas National Reserve ^[8]; at Paracas it nests in small, scattered colonies on slopes up to 5 km from the sea ^[2]. In October 2022 a breeding site was found at Pampa Pie de Candela, Tacna, 11.5 km from the coast at about 160 m elevation, with 15 nests and an estimated 30 pairs ^[6].

In northern Chile, surveys made between 2013 and 2017 placed its colonies of Arica, Pampa La Perdiz and Salar Grande 5 to 18 km inland, at 600 to 800 m elevation, and estimated at least 55308 pairs ^[9]. Added to the minimum of 2305 pairs Jahncke calculated for Paracas in 1994, the world population would be at least 57613 pairs, more than 150000 birds once immatures are counted ^[9].

Some birds turn up far from the sea: it has been recorded at 3800 m elevation in the district of Jangas, Peru, 90 km from the coast, and in January 2023 a fledgling reached La Paz, Bolivia, about 310 km from the Arica colonies ^[5].

It breeds in colonies and is strongly faithful to its natal colony and to its nest sites ^[2]. Each pair spends about 5 months on land, from arriving at the territory until the fledgling leaves, but because pairs are not synchronised, a single colony can show breeding activity over 10 months ^[9].

In the Paracas National Reserve, laying starts in June and fledglings leave the nests between late November and early December ^[8]. The Arica colony follows a similar calendar, April to December, whereas Pampa La Perdiz and Salar Grande, only 140 and 240 km farther south, breed from November to May; the authors suggest that each colony times hatching to one of the 2 spawning peaks of the anchoveta, in September and in March ^[9]. The chicks found in Tacna in October 2022 fit the calendar of Paracas and Arica ^[6].

An analysis of the mitochondrial gene ND1 separated 3 well-supported lineages, corresponding to Paracas, Arica and Salar Grande ^[2]. Paracas and Arica, which breed at the same time of year, share a haplotype, which points to some exchange of birds, while Salar Grande, on a different calendar, has a haplotype of its own ^[2].

Adults reach the colonies at least 45 minutes after sunset and call both in flight and from inside the cavities ^[9]. With automatic recorders at 2 Atacama Desert colonies, vocal activity began on average 86.7 minutes after sunset at Pampa Chaca and 102.9 minutes after it at Caleta Buena ^[10].

Researchers examined 95 stomach contents from adults caught on the Paracas Peninsula and La Vieja Island in 1996, 1999 and 2000: by weight, 54 % of what had been eaten was fish, 36 % cephalopods and 10 % crustaceans ^[8]. The anchoveta Engraulis ringens supplied 27.2 % of the total mass, and Pleuroncodes monodon was the leading crustacean, at 9.4 % ^[8].

The diet changed from year to year: cephalopods prevailed in 1996 and 2000, and fish in 1999, after the 1997-1998 El Niño, when anchoveta was its main prey; no anchoveta turned up in the 1996 and 2000 samples ^[8]. Its prey included mesopelagic fish that rise to the surface at night and squid with light organs, which the authors take as a sign that it partly feeds in the dark ^[8].

Nearly 10 % of the samples held remains that betray scavenging, and at sea it was seen hovering over carcasses of the sea lion Otaria byronia along with other storm petrels; 3 samples contained small bits of plastic and aluminium foil ^[8]. In at-sea censuses in 1998 and 2000, 90 % of the birds were beyond the continental shelf, up to 360 km from the coast, and the authors conclude that it feeds opportunistically on whatever it finds near the surface ^[8].

In Peru it is listed as Vulnerable in the official list of threatened wildlife species, approved by Supreme Decree N.° 004-2014-MINAGRI ^[3].

In the Paracas National Reserve, its breeding areas in the desert sector of Cerro Lechuza lie within a strict protection zone of the 2025-2030 Master Plan; entry and passage on foot or by vehicle are not allowed there, and research needs prior authorisation from the reserve's management ^[4].

In Chile, none of the 3 colonies studied between 2013 and 2017 lay inside a protected area; the threats recorded include roads, litter that blocks the entrances of the cavities, military exercises that destroy the salt crust, power lines, mines and power plants ^[9].

Artificial light attracts fledglings and brings them down on their flight to the sea: between 21 and 29 November 2017, 86 grounded birds were found in the city of Arica, 31 % of them dead, and at Salar Grande more than 20875 fledglings were estimated to die each year because of the lights of the mines ^[9]. To reduce the harm, the authors recommend switching off or dimming lights during the breeding season, aiming them so that they do not point at the sky, and rescuing grounded birds before dawn ^[9].

In Peru, young birds come down in Lima in November and December, which is put down to disorientation caused by the city lights ^[7]. The Pampa Pie de Candela breeding site in Tacna is crossed by a road and surrounded by farmland advancing near the valley of the Sama River ^[6].

According to distribution models under climate change scenarios up to 2080, the most affected area would be the southern edge of its breeding range, in the Chilean regions of Tarapacá and Antofagasta, which has no legal protection today; the authors warn that losing any local population could mean losing unique genetic diversity ^[2].

Grounded fledglings turn up in the middle of town: in Arica, most of those recorded in 2017 were near the Carlos Dittborn stadium and the street lights at the entrance to the Azapa road ^[9]. In the cities of northern Chile, groups of volunteers take part every year in rescuing and releasing them, and at Salar Grande the mining companies run rescue programmes, although the authors consider their effect marginal because many birds are eaten by vultures Cathartes aura after dawn ^[9].

In Peru, the 2025-2030 Master Plan of the Paracas National Reserve places breeding areas of the species in the desert zone of Cerro Lechuza, a strict protection zone where entry is not permitted ^[4]. At sea, IMARPE's 2019 cruises recorded it off the whole coast, mostly beyond the continental shelf, at mean distances of 40.3 to 56.9 nautical miles from land depending on the season; no sighting was closer than 5.9 nautical miles to the coast ^[7].