Justification of Red List Category
This species qualifies as Vulnerable because it has a very small breeding range at three or four locations, and is therefore susceptible to stochastic events or human impacts. It is likely to have been extirpated from one island some time ago, but the bulk of the population is presumably stable.
The world population may be no greater than 10,000 individuals. The estimate of global breeding population, based on on-the-ground counts of nests, is 2,777 breeding pairs (or 5,554 breeding individuals) (Hodum 2012).
The population is thought to be stable although the very small breeding range of the species renders it susceptible to stochastic events.
Pterodroma defilippiana is an east Pacific seabird, currently breeding on three or four islands off the coast of Chile. In the Desventuradas Islands, 10,000 or more birds occurred on San Ambrosio in 1970, with an additional 150-200 pairs on San Félix. The most recent estimate is 4,600 breeding individuals on San Ambrosio (Hodum 2012). In the Juan Fernández Islands, it has possibly been extirpated on Robinson Crusoe, and the population on Santa Clara was suggested at hundreds, possibly thousands, in 1986, but available habitat was found for only 100-200 individuals in 1991. A recent estimate for the Juan Fernández Islands was 954 breeding individuals, of which 327 breeding pairs are on Santa Clara (Hodum 2012). The remaining breeding birds are on small rock stacks immediately offshore of Robinson Crusoe.
It ranges at sea in the nearby Peru Current, south of the equator (Roberson and Bailey 1991, Spear et al. 1992).
This species breeds on sheltered cliff-ledges, crevices, caverns and amongst boulders at the foot of lava cliffs. It nests colonially, with eggs apparently laid late July-early August, chicks hatching in September-early October and colonies abandoned in December (Hodum 2012). However, it has been reported breeding in February on San Félix.
While the majority of the breeding population appear to be on predator-free islands the presence of cats, coati and rats may continue to prevent recovery on Robinson Crusoe and cats have caused extensive mortality on San Félix. Rats are present on many islands but it is unclear whether they are causing declines. Goats are present on San Ambrosio, but their impacts on the species are unknown.
Conservation Actions Underway
The Juan Fernández Islands were designated as a National Park in 1935 (protected from 1967) and a Biosphere Reserve in 1977. The Chilean government began a habitat restoration programme in 1997 (J. C. Torres-Mura in litt. 1999), and the islands have been nominated for World Heritage listing (Hulm 1995). Mapping of breeding colonies and a population estimate for all breeding locations except for San Félix were completed in 2010-2012 by Oikonos Ecosystem Knowledge. A long-term breeding season monitoring program was established on Santa Clara in 2010 by Oikonos. Monitoring on San Ambrosio is being planned by Oikonos for the 2016 breeding season, in collaboration with local fishermen. Oikonos has also undertaken awareness-building programs with the local community in Juan Fernández.
Conservation Actions Proposed
Continuing the long-term monitoring programme, and conduct assessments of foraging areas during the breeding season and any possible interactions with fisheries. Remove all introduced mammals, initially within intensively managed, fenced, feasibility study areas.
26 cm. Small, typical M marked gadfly petrel. Dark grey upperparts with sharp M mark. White forehead but dark grey cap and mask, extending to grey half-collar on upper breast. Dark grey rump and uppertail-coverts. Paler outer tail feathers. White throat and lower chest/belly. Predominantly white underwing, but black tip and narrow trailing edge, extending to leading edge. Similar spp. Separated from most other small gadfly petrels by whiter underwing. Cook's Petrel P. cookii has shorter and thinner bill and shorter tail. Stejneger's Petrel P. longirostris has paler crown and nape, and lacks darker central tail feathers. Pycroft's Petrel P. pycrofti is possibly inseparable, but ranges may not overlap.
Text account compilers
Fjagesund, T., Clay, R.P., Hermes, C., Bird, J., Martin, R., Moreno, R., Stuart, A., Temple, H.
Torres-Mura, J., Hodum, P.
BirdLife International (2020) Species factsheet: Pterodroma defilippiana. Downloaded from http://www.birdlife.org on 22/10/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/10/2020.