Guadalupe Storm-Petrel Hydrobates macrodactylus Scientific name definitions

The Guadalupe Storm-Petrel was described in 1887, it was said to be an abundant breeder on Guadalupe Island, Mexico in 1906, and the last records of birds on Guadalupe come from 1912. It then disappeared and has not been seen again! Some consider the species extinct, while other hold out hope that it still exists. Predation by introduced rats, and habitat alteration by introduced goats are thought to be the culprits in the demise of the species. However, other storm-petrels have survived on the island, so perhaps another factor was involved? There is nothing known about the at-sea distribution of this storm-petrel. It was large and dark, with a white rump. It is thought to have been closely related to the Leach's Storm-Petrel (Hydrobates leucorhous) complex, and although larger than the Leach’s it would be very difficult to separate from it without detailed study. The Guadalupe Storm-Petrel processed a broader and thicker bill, and apparently paler underwings than white-rumped Leach's Storm-Petrel.

22·5–24 cm; wingspan 50·5–52 cm (1 Howell, S. N. G. (2012). Petrels, Albatrosses, and Storm-Petrels of North America: A Photographic Guide. Princeton University Press, Princeton, New Jersey, USA. Close ). Medium-large, fork-tailed and white-rumped storm petrel (see photo of specimen ). Blackish-brown upperparts with paler grey wingbar (principally on greater coverts, reaching almost to wing-bend), slaty sheen to head and back, and dark-tipped white uppertail patch that extends to lateral tail-coverts, and divided by a darker but variable median stripe; tail moderately forked; underparts slightly paler than upperparts. Probably very difficult to distinguish from the Leach's Storm-Petrel (Hydrobates leucorhous) subspecies socorroensis, which also breeds in summer on Guadalupe, although the present species’ bill is broader- and deeper-based, with a paler underwing and longer and deeper-forked tail.

Probably related to the species that may be separated in genus Cymochorea (see Leach's Storm-Petrel (Hydrobates leucorhous)). Monotypic.

Guadalupe Island, off northwestern Mexico. Possibly extinct (2 BirdLife International (2013). IUCN Red List for birds. URL: http://www.birdlife.org (download Aug 2013). Close ).

Marine, but degree of pelagic behaviour unknown; nested on ground within forest, ca. 800 m above sea-level (3 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ).

Few details known, but eggs laid March to June; chicks reported as late as August. Nested in burrows lined with leaves and pine needles, under pines (Pinus radiata) or cypress (Cupressus guadalupensis) groves. Lays single white egg finely spotted darker, mean size 35.7 mm × 27 mm. No further information (3 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ).

CRITICALLY ENDANGERED (POSSIBLY EXTINCT). Population estimated at no more than 50 individuals; may persist on Guadalupe, off Mexico, 280 km west of Baja California. The species was abundant in 1906 (4 Thayer, J. E., and O. Bangs (1908). The present state of the Ornis of Guadaloupe Island. Condor 10(3):101–106. Close ), but the last record of a breeding bird was in August 1912 (5 Collar, N. J., L. P. Gonzaga, N. Krabbe, A. Madroño, L. G. Naranjo, T. A. Parker, and D. C. Wege (1992). Threatened Birds of the Americas. The ICBP/IUCN Red Data Book. Part 2. Third Edition. ICBP, Cambridge, UK. Close ). Searches in midsummer 1922, April 1925 (not the breeding grounds) and the early 1970s (not all forested areas) failed to find it, although there has been no thorough survey at the appropriate season since 1906 (5 Collar, N. J., L. P. Gonzaga, N. Krabbe, A. Madroño, L. G. Naranjo, T. A. Parker, and D. C. Wege (1992). Threatened Birds of the Americas. The ICBP/IUCN Red Data Book. Part 2. Third Edition. ICBP, Cambridge, UK. Close ). Relatively recent reports of storm-petrels calling at night and the apparent persistence of breeding Leach's Storm-Petrel (Hydrobates leucorhous) raises some hope that it may survive, although this is unlikely unless it is able to nest in rock crevices in areas inaccessible to cats. Main cause of its demise was probably heavy predation by feral cats (Felis catus), compounded by goats destroying and degrading nesting habitat; nearly 35,000 goats were removed in 1970/71, and a comprehensive program resulted in complete eradication in 2004 (6 Garcillán, P. P., E. Ezcurra, and E. Vega (2008). Guadalupe Island: lost paradise recovered? Overgrazing impact on extinction in a remote oceanic island as estimated through accumulation functions. Biodiversity and Conservation 17(7):1613-1625. Close ). Guadalupe is now a Biosphere Reserve (IUCN Cat. VI; 4770 km²), but until recently there was little active management. The island should be completely surveyed during the breeding season; observers on pelagic trips off the Pacific coast of California and Mexico are urged to be vigilant.