Behaviour Audouin's Gull is a medium sized gull largely restricted to the Mediterranean. It is partially migratory and dispersive³⁰. It breeds in large monospecific colonies ranging from 10 up to 10,000 pairs³⁰ at a density of up to 1 nest/ sq. m³⁰ . Egg-laying takes place in the second half of April until the beginning of May, and peak hatching occurs in late May³⁰, with fledging mainly in the first two weeks of July. It has a large foraging range while breeding, and has been recorded up to 200 km from the colony²⁷. After breeding the birds disperse widely around the Mediterranean coast^13,30. Almost all juveniles and some adults migrate past Gibraltar during July-October³¹, to winter on the North African coast³⁰. During the winter it roosts in flocks of several thousand³¹. It returns to its breeding sites between late February and mid April³⁰. First year birds remain in the non-breeding range throughout the summer³². Very high colony-site fidelity is probably related to previous breeding success. However, in the Aegean Islands, birds return to the same "island group" but not necessarily to the same islet. At the Ebro Delta, Spain, c.1,400 breeders disperse to other colonies every year, generating marked fluctuations at those sites¹⁵. The Audouin's Gull is one of the few species of Larid to show nocturnal foraging patterns, which may be linked to fisheries activities; arrivals and departures from the Ebro Delta colony are in accordance with the trawling timetable²⁷. The species scavenges around fishing vessels, and uses discards extensively and very efficiently²⁷. The species's association with fisheries is more pronounced in the western than in the central and eastern Mediterranean³⁴. A trawler moratorium off the Ebro Delta has caused decreased food availability to birds and has also negatively affected breeding success, possibly by necessitating increased foraging ranges³⁶. Habitat Breeding Colonies are located on exposed rocky cliffs and on offshore islands or islets³², normally not more than 50 m above sea level³². The Ebro delta colony is located on saltmarsh and a sandy peninsula³¹. In the Aegean it breeds on uninhabited islands sloping gently to the sea and covered with large stones, eryngo Eryngium, grass and low bushes of Pistacia lentiscus³². Characteristics of habitats used differ from region to region and even within the same areas in different years: altitude ranges from close to sea-level to 100 m, vegetation cover from bare rocks to 85% bush cover, and slope from 0-90^o. Medium vegetation cover is preferred, and this probably provides chicks with shelter from heat and predators. The concentration of breeding colonies in the western Mediterranean is possibly related to the lower water salinity and higher abundance of clupeids. Non-breeding During the non-breeding season the species prefers sheltered bays, either flat and shingly, sandy or with cliffed margins³². It sometimes visits seaside resorts and marinas lured by food, and it especially likes areas on beaches where freshwater occurs, such as stream mouths or floods³². It is a coastal species, rarely occurring inland and generally not travelling far offshore³². Diet This species was historically thought to feed far out to sea, but more recent observations show that it feeds regularly along the coast. The diet consists mostly of epipelagic fish, especially Clupeiformes, for which it sometimes forages at night, taking advantage of its prey's diel migration patterns²⁷ and of commercial fishing by purse-seine netting³⁴. It is also known to take some aquatic and terrestrial invertebrates, small birds and plant material such as the peanut Arachis, olive Olea, and grain³². The Ebro delta colony feeds largely on fish waste dumped by boats fishing nearby³³. The species is also known to feed on food discarded at tourist beaches³², and during a moratorium on trawling, it was found to forage in marshes, rice fields and occasionally at refuse tips^27,30. Diet during the breeding season has been found to vary between colonies due to fishing practices that target different species in the respective areas³⁴. Breeding site The nests is a shallow scrape lined with available debris and vegetation³². It is placed among rocks and vegetation³⁰. Foraging range During the non-breeding season, surveys in Morocco found birds no further than 46 km from the coast³⁷, and generally <40 km from the colony seems to be the norm²⁷. However, the maximum recorded foraging range from a colony was 160 km²⁷. The species primarily forages in coastal and continental shelf areas between 5 and 15 nautical miles (nm) offshore. A radius of 15 nm from the Ebro Delta would ensure the protection of 30% of the birds (or 30% of the foraging area). A 30 nm radius would protect 80% of birds. These distances could be reduced in colonies where the surrounding continental shelf is narrower³⁸. Juveniles tend to forage in upwelling zones, whereas subadults and adults are more independent of these sites³⁹.

Red List Category

Red List Criteria

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Near Threatened
• 2006
  Near Threatened
• 2004
  Near Threatened

The global population (excluding Europe) is estimated to be 19,200 pairs (Lambertini 1996), with 18,000-19,000 pairs in Europe (BirdLife International 2004), giving a total of 57,600 individuals.

Decreasing

The trawling fishery off the Ebro Delta is regarded as unsustainable and its collapse would probably result in a decline in the breeding population due to the increase in density-dependence^15,25. A similar outcome would arise if waste from the trawlers were used industrially to produce food for domestic animals, as occurs in other areas, rather than being dumped near the Ebro colony.More important could be the reduction of small-pelagic fish stocks, the main natural prey for Audouin's Gull, due to increasingly high fishing pressure around the breeding grounds, owing partly to high demand by tuna-farming²⁸. Other important threats include coastal tourism developments, regulation of the river Ebro, mortality due to entanglement in fishing gear (mainly longlines and sporting lines)^17,18, and predation by terrestrial predators, such as red fox Vulpes vulpes, badger Meles meles and domestic dogs^15,19. Predation by sympatric Yellow-legged Gull L. michahellis can be high at some breeding colonies, especially when densities of Audouin's Gulls are low^6,11,16. Predation on chicks by black rats Rattus rattus has a negative impact at some breeding colonies³⁵. Nevertheless Audouin's Gull shows a very nomadic breeding site selection and high dispersal rates from year to year, probably avoiding large densities of Yellow-legged Gulls^20,21,22. Peregrines Falco peregrinus, other raptors, some herons and snakes can also prey on adults and nests but only accidentally and locally^23,24. Very high levels of mercury and other pollutants are found in this species¹³, partly due to the consumption of discards ²⁹, thus posing a potential threat, although no negative effects have been demonstrated. Current marine wind-farm projects, particularly around the main breeding colony (Ebro Delta), could also represent a serious threat. Overgrazing of some islets by goats in the east of its breeding range may reduce breeding success. Natal and breeding dispersal are extremely high ensuring genetic mixing and buffering against bad local environmental conditions through emigration and colonisation^9,25.

Conservation Actions Underway
CMS Appendix I and II. A European action plan was published in 1996. The ecology of this species, particularly its breeding and foraging behaviour and demography and population dynamics, has been extensively studied. Lebanon prepared an action plan to restore the breeding population back to Palm Islands Nature reserve. Several LIFE Nature projects have been implemented between 1992 and 2006 in Spain and Italy, contributing to successful recolonisation of breeding islands and development of safe line-fishing techniques. Control of invasive black rats Rattus rattus has been effective at some colonies³⁵.

Conservation Actions Proposed
Continue to monitor breeding colonies. Identify appropriate actions to mitigate against the key threats. Implement strict fishery management policies in the species's range. Increase the area of suitable coastal habitat that is protected from development and degradation. Enforce laws designed to minimise marine pollution. Implement measures to reduce mortality in fishing gear, perhaps facilitated by legislation. Ensure regulation of the river Ebro benefits the species.