Justification of Red List Category
This species has undergone extremely rapid declines in the past three generations (60 years) and is therefore classified as Critically Endangered.
The global population estimate is best placed in the range of 10,000-19,999 individuals, based on an estimate of 4,500-5,000 active nests (representing 9,000-10,000 mature individuals) in 2008 (I. Guzmán in litt. 2008).
This species suffered from the impacts of introduced predators and agricultural expansion on its nesting islands, resulting in very rapid declines up until the 1980s (Coulter et al. 1981, Cruz and Cruz 1987). Declines since then appear to have been much slower (Valarezo 2006), although data is relatively sparse; nevertheless, given the species's long generation time (20 years), it has still undergone extremely rapid declines over the past 60 years (three generations).
Pterodroma phaeopygia is endemic to the Galápagos Islands, Ecuador, breeding on Santa Cruz, Floreana, Santiago, San Cristóbal, Isabela and possibly other islands in the archipelago (Cruz and Cruz 1987, H. Vargas and F. Cruz in litt. 2000). Between 1978 and 1980, populations on the islands were estimated at 9,000 pairs on Santa Cruz (Baker 1980), c.11,250 on Santiago, and c.6,750 on Floreana and San Cristóbal (Tomkins 1985). By 1985, the Santa Cruz population had plummeted to 1,000 pairs, that on Santiago to less than 500 pairs (Cruz and Cruz 1987), and numbers on Floreana and presumably San Cristóbal were estimated to have declined to c.2,000 pairs (Coulter et al. 1981). An extensive survey of Santa Cruz in 2005 located c.300 previously unknown nests, but the island population totalled just 700 pairs (Valarezo 2006); a further survey in 2010 calculated 1,135 pairs (Valarezo and Heitmann 2011). Estimates in 2008 suggested a total of 4,500-5,000 active nests on all five islands (I. Guzmán in litt. 2008). Birds forage around the islands, but also disperse east and north towards South America and up to 2,000 km south (Spear et al. 1995). The species has recently been recorded off the coast of Peru, and records in Baja California could be this species or Pterodroma sandwichensis (Carboneras et al. 2015).
It breeds in the humid highlands at 300-900 m, in burrows or natural cavities, on slopes, in craters, sinkholes, lava tunnels and gullies usually in close proximity to Miconia plants (Baker 1980, Cruz and Cruz 1987, 1996). It feeds mostly on squid, fish and crustaceans (Castro and Phillips 1996). On San Cristóbal, nests were primarily located along ravines in areas of dense Miconia robinsoniana and native fern cover, with the majority of egg-laying taking place between May and October, peaking in August (Cruz-Delgado et al. 2010a).
Like many species on the Galápagos, the Galapagos Petrel is threatened by a number of invasive species. Brown and house rats represent a significant threat, with predation by rats found to be the primary cause of nest failure (72%) in a study of colonies on San Cristóbal in 2002-2003 (Cruz-Delgado et al. 2010). Cats and pigs have been eradicated from Baltra and Santiago respectively, although are still thought to represent a significant threat to the Galapagos Petrel on other islands through predation of eggs, young and adults. Goats, donkeys, dogs and other introduced mammals still exist in some areas of the petrel’s range but are thought to represent a much less significant threat. Depredation also occurs from native species, primarily the the Short-eared Owl Asio flammeus and the Galapagos Hawk Buteo galapagoensis, however, there is no clear reason to suspect this is occurring at levels high enough to drive declines.
El Niño events seem to have a detrimental impact on nesting and productivity. This species is potentially susceptible to changes in sea temperature, such as due to ENSO events and climate change, which may affect food supplies (D. Wiedenfeld in litt. 2012, BirdLife International unpubl. data).Some areas of breeding habitat have been lost to the invasive Blackberry plant, and less so to the Cinchona. Although habitat has previously been threatened by farming activity, the majority of breeding sites are now within Areas of Conservation within the zoning system of protected areas within the Gálapagos National Park, with most colonies fenced or livestock removed from the area.
Conservation Actions Underway
CMS Appendix I. In 1982, predator control commenced in the Cerro Pajas colony (c.2,000 pairs) on Floreana (Cruz and Cruz 1996). Predator control involving intensive rat baiting around known colonies and petrel monitoring currently continues on Floreana, Santa Cruz, San Cristóbal and Santiago (H. Vargas and F. Cruz in litt. 2000, D. Wiedenfeld in litt. 2012). In early 2009, it was confirmed that goats have been successfully eradicated from Santiago (American Bird Conservancy 2009). A small number of burrows have recently been discovered on Alcedo, Isabela (Cruz-Delgado 2005). The islands are a national park and were declared a World Heritage Site in 1979. World Heritage Site designation encourages Ecuador to work carefully to enact suitable conservation laws and implement existing laws to protect the unique fauna and flora of the Galápagos Islands. There are proposals to protect more marine key biodiversity areas within the Galápagos Marine Reserve by amending the existing marine zoning scheme to reduce the impact from fishing (Edgar et al. 2008). The wind turbine development includes a series of mitigation and enhancement measures that will be instituted during implementation, many focusing on the Galapagos Petrel, and it is intended that these measures will not only act to minimise impacts but may actually help increase the population. A long-term monitoring programme is included as part of the project activity and ongoing operations (Anon. 2008). Exotic vegetation is being controlled with the help of local landowners on Santa Cruz (Valarezo and Heitmann 2011).
43 cm. Large, long-winged gadfly petrel. Variable amounts of black marking on white forehead. Similar spp. Exceedingly similar to Hawaiian Petrel P. sandwichensis and not certainly distinguishable at sea. On average, has longer wing, tarsus and bill. P. sandwichensis lacks black forehead markings. Voice Four-syllable kee-kee-kee-koo, the last note drawn out.
Text account compilers
Martin, R., McClellan, R., Sharpe, C.J., Stuart, A., Calvert, R., Stuart, T., Symes, A., Temple, H., Westrip, J., Clay, R.P., Fjagesund, T., Ashpole, J, Bird, J., Hermes, C., Isherwood, I., Lascelles, B.
Brooke, M., Vargas, H., Cruz, F., Hennessey, A., Allport, G., Wiedenfeld, D.
BirdLife International (2020) Species factsheet: Pterodroma phaeopygia. Downloaded from http://www.birdlife.org on 20/02/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/02/2020.