Waved albatross

Phoebastria irrorata is an albatross of the family Diomedeidae described by Salvin in 1883 ^[1]. Peru's official list of threatened wildlife calls it «albatros de las Galápagos» ^[2]. Nearly all of its population breeds on the Galápagos island of Española (Ecuador), and a few pairs breed on Isla de la Plata, near the mainland; while incubating and raising larger chicks, adults travel to feed in the coastal upwelling off Peru ^[3]. The IUCN Red List classifies it as Critically Endangered in its 2018 assessment ^[4], and the Peruvian list approved in 2014 places it in the Critically Endangered category ^[2].

For nesting it depends almost entirely on a single island: nearly all birds of this species breed on Española Island (1° 20′ S, 89° 40′ W), with large colonies at its eastern and western ends, Punta Cevallos and Punta Suárez ^[5]. By the 2001 calculations, the living adult population of Española added up to a minimum of between 31818 and 34694 birds; on Isla de la Plata only 3 non-breeding adults were found in 2000, and in December 1998 up to 11 non-breeding birds were seen on Genovesa Island ^[6]. The La Plata colony, of 10 to 20 pairs, lies about 850 km from the Peruvian upwelling ^[3].

Away from the islands it lives mainly in the northern part of the Humboldt Current ^[7]. It can reach much farther south: 13 sightings compiled in Chile since the 1980s place it as far as 38° S, 4391 km south of the Galápagos, and up to 920 km offshore from the South American coast, and 76.9 % of them fell outside the breeding season ^[8]. During the 2015-2016 El Niño and the 2017 coastal El Niño it was seen in southern Peru between 1300 and 1400 km south of its usual limits ^[9].

In the colonies of Española Island, then called Hood, studied in 1970-1971, incubation lasted 60 days on average and raising the chick to its first flight took 167 days ^[7]. The species keeps no stable nest site: adults shift the egg over long stretches, which causes many losses, and some pairs left without their own adopted another bird's deserted egg and raised the chick ^[7].

Young birds may come back to the colony from 2 years of age, usually very late in the season, but most do not attempt to breed until they are 5 or 6 ^[5]. Of the birds ringed as adults in 1999 that were expected to be still alive, on average 68 % bred each year between 2003 and 2005 ^[5]. The greatest documented age was 38 years, a figure capped by how long the ringing programme had run ^[5].

Although pairs are socially monogamous, copulations outside the pair are frequent: of 3661 copulation attempts noted over 3 seasons between identified birds, more than 60 % of those involving a breeder were with an outside bird ^[10]. Males usually return to the colony ahead of their partner, nearly always by 6 to 10 days, which between 76.3 % and 96.6 % of them did depending on the year; genetic tests showed that between 14 % and 21 % of chicks were not sired by the male raising them ^[10].

It is a sexually dimorphic species: at fledging, male chicks were clearly larger than females, although over 3 consecutive seasons both hatched and fledged in similar proportions and with the same survival ^[11]. The excess of females among adults is most probably explained by adult mortality that differs between the sexes, including more male deaths in fisheries ^[11].

The way it feeds changes with the breeding stage. In 2003, in the weeks when chicks were still very small, parents tracked by GPS made short trips to waters less than 600 m deep lying north-northwest of Española; nearly all of their activity, 92 %, was recorded within 100 km of the colony, with no marked difference between males and females ^[12]. During incubation and the rearing of older chicks, by contrast, adults from Punta Cevallos feed mainly in the Peruvian upwelling, about 1350 km to the southeast ^[3].

In 2008, all long trips by birds tracked from Española and from Isla de la Plata ended on the Peruvian coast near the upwelling; the southernmost latitude of those trips had a median of 7.18° S for Punta Cevallos birds and 7.98° S for Punta Suárez birds, against 4.86° S for La Plata birds, which made more and shorter trips ^[3].

The chicks Harris studied were fed mostly squid and fish ^[7]. Stable isotopes measured in adult blood gave higher δ15N values in males, a sign that they eat prey of a somewhat higher trophic level than females; δ13C values, with no difference between the sexes, point to both feeding in pelagic waters, in the Galápagos as well as in the Peruvian upwelling ^[13].

In Peru it takes advantage of fishing activity. Between 2023 and 2024, 4 groups of 8 to 210 birds were seen eating anchoveta (Engraulis ringens) trapped in industrial purse seines or leaping beside the floats, off the north-central coast; IMARPE observers had already seen the same since 2015 ^[14]. In the south, alongside the artisanal fishery for jumbo squid (Dosidicus gigas), it was present all year round between 2015 and 2017 and fed mostly on pelagic fish at the surface ^[9].

Its global category is Critically Endangered ^[4]. In Peru it is classified as Critically Endangered, and the regulation that lists it prohibits the hunting, capture, possession, trade, transport and export for commercial purposes of the species included ^[2].

The breeding population of Española is shrinking: the 2007 count gave 6045 pairs at Punta Suárez and Punta Cevallos, 88.1 % of the 6857 of 2001, and the data suggest a fall of close to 42 % between 1994 and 2007 ^[5]. Annual adult survival, 0.92 to 0.93 in normal years and 0.859 in a mild El Niño year, stayed below the 0.953 estimated for the 1960s, and a model built on those rates gave annual growth of 0.9615, typical of a population that is getting smaller ^[5].

According to the authors of the 2007 census, the death of adults in Peru's artisanal fishery remains the most convincing explanation for that decline; plastic, by contrast, looks like a minor threat, as only 3 of 43 dead birds examined in 2007 (7.0 %) had any in the proventriculus ^[5]. At 11 ports on Peru's northern and central coast, interviews with 361 fishers held between April 2022 and June 2023 recorded bycatch at every port but one; the estimate exceeds 1200 interactions a year, counting birds freed alive, hurt or possibly dead, and most happen on surface longlines and in gillnets ^[15]. The risk was concentrated in fishing for large pelagic fish, with J-shaped hooks and with large-mesh nets, and the study recommends management suited to each area and more cooperation between Peru and Ecuador ^[15].

Diseases are also monitored at the colony. Between November 2013 and January 2014, 14 chicks with avian pox-like lesions were found on Española, consistent with avipoxvirus in the 5 samples examined under the microscope, and 6 of those 14 died ^[16]. In 2017 cloacal samples were taken from 59 albatrosses and 21 of them (35.6 %), all from Punta Suárez, held a bacterium of a type close to avian strains of Chlamydia abortus ^[17]. In 2023, 51 birds from Punta Suárez and Punta Cevallos were tested and none was positive for highly pathogenic avian influenza H5N1 ^[18].

It does not nest in Peru: its only two colonies are on Española and La Plata, both in Ecuador ^[3]. The published records in Peru are at sea, from fishing vessels: between November 2023 and April 2024, groups of 8 to 210 birds were seen between 30 and 167 km off the coast facing Culebras, Chimbote, Chao and La Gramita, and IMARPE observers logged it in 2015 and 2022 between Punta Eten and Punta Lomitas, with up to 230 birds in a single sighting ^[14]. In the south of the country it was frequent between 2015 and 2017, during El Niño, alongside the artisanal jumbo squid fleet ^[9].