Justification of Red List Category
This poorly known species is considered Vulnerable because it has a very small population. Numbers are assumed to be stable, although there are a number of potential threats, which may be having an impact.
Snow and Snow (1969) estimated 600-800 mature individuals which Wetlands International (2002) interpreted to equate to 900-1,200 individuals. This may be an overestimate (Aguirre 2007, D. Wiedenfeld in litt. 2012).
Numbers are assumed to be stable although there are a number of potential threats which may be having an impact.
Larus fuliginosus breeds only in the Galápagos Islands, Ecuador. It is widespread throughout the archipelago, with possibly the most dense populations found at Puerto Ayora (Santa Cruz) (Jackson 1985, H. Vargas and F. Cruz in litt. 2000), Puerto Baquerizo Moreno (San Cristóbal) and Puerto Villamil (Isabela) (H. Vargas and F. Cruz in litt. 2000). In 1963, a survey of 56 km of coastline on the south and east of Santa Cruz found eight territories, which was extrapolated over the remaining coastline in the archipelago to give an estimate of 300-400 pairs. This has been considered an overestimate, and an estimate by Aguirre (2007) determined only 81 individuals in the largest population, on Santa Cruz Island. If extrapolated, this would produce a total population of only 243 individuals (D. Wiedenfeld in litt. 2012). It has been suggested that the tiny population is probably a consequence of its confinement to linear feeding grounds of restricted range, which provide a limited food supply for much of the year (Snow and Snow 1969).
It nests solitarily in sheltered places near lagoons, pools and other calm water, usually close to the sea (Snow and Snow 1969). It is a scavenger, with local concentrations of birds in areas of high food availability, such as harbours, and will associate with boats (Burger and Gochfeld 1996). However, it also takes seabird eggs, juvenile marine iguana Amblyrhynchus cristatus, small fish and crustaceans (Snow and Snow 1969). It nests in scrapes on sandy beaches or low outcrops close to water, and lays two eggs (Burger and Gochfeld 1996). Territories are large (Snow and Snow 1969).
Lava Gulls are primarily threatened by fishing activities, especially being caught on hooks as bycatch (Wiedenfeld and Jiménez 2008, Pott and Wiedenfeld 2017). Newcastle disease, brought into the Galápagos with domestic chickens, is thought to pose a particularly high risk of mortality and morbidity in wild Lava Gulls due to their endemic nature and small population size (Gottdenker et al. 2005). It is also thought they experience some direct persecution, although it is believed the numbers included are very low (Wiedenfeld and Jiménez-Uzcátegui 2008). Invasive non-native species also pose a threat, particularly House Rats Rattus rattus, cats Felis catus and dogs Canis familiaris which have been shown to predate Lava Gull nests (Wiedenfeld and Jiménez-Uzcátegui 2008, Cepeda and Cruz 1994).
Conservation Actions Underway
Although much of the island archipelago is protected in the Galápagos National Park, the greatest densities of this species may occur in the three main ports (Wiedenfeld 2006), and these urban areas are not part of the national park (H. Vargas and F. Cruz in litt. 2000). The islands were declared a World Heritage Site in 1979.
53 cm. Unmistakable, all-dark gull. Overall dark ashy-grey, darkest on wings and palest on belly and vent. Noticeably darker hood with white eyelids. Black bare parts, red inside of mouth. Immature browner.
Text account compilers
Martin, R., Palmer-Newton, A., Pilgrim, J., McClellan, R., Benstead, P., Sharpe, C.J., Stuart, A., Symes, A.
Vargas, H., Cruz, F., Wiedenfeld, D.
BirdLife International (2019) Species factsheet: Larus fuliginosus. Downloaded from http://www.birdlife.org on 20/10/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/10/2019.