Grey gull  (Larus modestus)

The grey gull is classified as Least Concern (LC) on the IUCN Red List (1).

Although rather indistinct in appearance, the grey gull (Larus modestus) is unusual among gulls for nesting in the extremely arid and barren Atacama Desert of northern Chile. Its dark grey plumage is thought to be an adaptation to life in this hot, sunny place, as the melanin (a skin pigment) prevents its feathers from being faded and weakened by the light, while dark colours are better at radiating heat than white, preventing the gull from overheating (3). 

Outside the breeding season, the grey gull is largely smoky grey, with a solid brownish hood, paler underparts, and a grey tail with a black band and white tip. The forehead, lores (area between the eye and bill), and a narrow ring around the eye are all white (2) (4), and the flight feathers are blackish with white-tipped secondaries. During the breeding season, the adult grey gull develops a pale head (4). 

The grey gull is a medium-sized gull with a slender black bill and black legs (4). Its call is a yelping “kyow” and a growled, rising “grrraaahh”, as well as a low moan and shrill cries (5).

The grey gull is found along the Pacific coastline of South America, ranging from Ecuador and Peru, to central Chile. For many years it was a mystery where this species bred. Courtship behaviours were observed on the Chilean coast, but the location of the nests was unknown. It was not until the 1970s that it was discovered that the grey gull breeds deep into the extremely arid Atacama Desert in northern Chile (3) (6).

Outside of the breeding season, the grey gull is found feeding along rocky coastlines, on sandy beaches and around river mouths and inshore waters. It may fly out to sea to feed, but rarely travels far from the coast. 

During the breeding season, the grey gull builds its nest on the ground amongst rocks in barren montane deserts that lack any vegetation and water. This gull commutes up to 100 kilometres each day from the inland colonies to the sea. These deserts have few or no predators making them extremely safe for nesting (2) (3) (4) (5) (6).

Outside of the breeding season, the grey gull disperses along the western coastline of South America, feeding mainly on small crustaceans. It usually feeds on the ground around the wave washed zone of sandy beaches, running back and forth between receding waves (4), but it may also scavenge in harbours and follow fishing boats (6). The grey gull may also forage at sea with other seabirds for schools of fish (4). 

The grey gull breeds in large colonies between November and January, when a simple nest is scraped into the sand of the Atacama Desert. Between 1 and 3 eggs are laid and incubated for 29 to 31 days. One adult attends the clutch while the other commutes to the coast after dark to feed, returning to the nest shortly before dawn. Young grey gulls grow slower than any other gull species, and are unable to fly until they reach around 40 days of age (2).

Although not currently considered to be threatened with extinction, the grey gull has a relatively small population that is thought to be in decline. Egg collection can be a problem and as many as 30,000 eggs were taken from a single colony during one notable event. However, the remoteness of its breeding habitat should limit the severity of this exploitation. Extreme El Niño events can also cause breeding failures, as they limit the foraging opportunities of breeding birds, leading to malnutrition and starvation (2) (4) (6).

The grey gull has not been the target of any known conservation measures.

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

Find out more about bird conservation in the Americas:

• American Bird Conservancy:
  http://www.abcbirds.org/

More information on the grey gull and other bird species:

• BirdLife International:
  http://birdlife.org/