Grey Gull

The Grey Gull, or Garuma Gull (Leucophaeus modestus), presents a medium-sized silhouette, typical of gulls, with a length of approximately 45 cm and a weight ranging from 360 to 400 grams. In the summer, its head is adorned with pristine white feathers, transitioning to a brownish-grey hue in the winter months. The body and wings are cloaked in grey, with the dorsal surface a shade darker than the ventral. In flight, one can observe the striking contrast of black flight feathers against the white-tipped inner primaries and secondaries. A band of black, edged with white, graces the tail. Both legs and beak are a stark black, and the eyes are a deep brown.

Identification Tips

When identifying the Grey Gull, look for the seasonal changes in head coloration, the grey body, and the distinctive black and white pattern on the tail and wingtips. The black legs and beak are also key identifiers, setting it apart from other gull species.

Habitat

The Grey Gull is a coastal bird, favoring sandy beaches and mudflats along the western coasts of South America. It is uniquely adapted to breed in the arid conditions of the Atacama Desert.

Distribution

This gull breeds inland in the Atacama Desert of northern Chile. Outside the breeding season, it can be found along the Pacific coast, from southern Ecuador through Peru to south-central Chile. It has also been recorded as a vagrant in locations such as the Falkland Islands, South Georgia, the South Sandwich Islands, Mexico, the Galapagos, Guatemala, Brazil, Argentina, Panama, and even as far north as Florida.

Behaviour

The Grey Gull is a remarkable species, breeding in the inhospitable Atacama Desert, far from the coast. It was not until 1945 that the mystery of their breeding grounds was solved, revealing their preference for a predator-scarce environment. Parents exhibit a remarkable dedication, traveling up to 100 km to the sea to provide sustenance for their chicks.

Song & Calls

The vocalizations of the Grey Gull bear resemblance to the laughing gull, a series of calls that can be heard along the coastal regions where they reside.

Breeding

Nests are simple scrapes in the sand, often situated near rocks in the waterless expanses of the desert. The gulls employ various thermo-regulatory behaviors to protect their eggs and chicks from the extreme temperatures. The eggs have evolved to minimize water loss through evaporation, a critical adaptation for survival in such a dry habitat.

Diet and Feeding

The Grey Gull's diet consists of invertebrates, which it forages for by probing the sediment on beaches and mudflats. It also consumes fish, ragworms, and will scavenge for offal, occasionally following fishing boats for scraps.

Conservation status

Despite a restricted breeding range and a limited wintering range, the Grey Gull is classified as "Least Concern" by the IUCN. The population is believed to be in decline, but the overall numbers are still large enough to avoid a more threatened status.

References

• BirdLife International (2012). "Larus modestus". IUCN Red List of Threatened Species. 2012.
• Josep del Hoyo, Andrew Elliott, Jordi Sargatal (Eds.): Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions 1996.
• "Leucophaeus modestus". Neotropical Birds Online. Cornell Lab of Ornithology.
• Guerra, Carlos G.; Aguilar, Roberto E.; Fitzpatrick, Lloyd C. (1988). "Water Vapor Conductance in Gray Gulls (Larus modestus) Eggs: Adaptation to Desert Nesting". Colonial Waterbirds. 11 (1): 107–109.