Overview

Brief Summary

Biology

Arriving at the nesting sites between late March and early April, Audouin's gull forms colonies from a few pairs to several thousand pairs. Each pair faithfully returns to the same breeding colony each year, but different nesting sites are used depending on the success of the previous year's clutch. Between late April and early May the female lays two to three eggs (9) and incubates them for three weeks (2). The chicks fledge in mid July, when both adults and young leave the colony for the wintering grounds (2). Audouin's gull feeds along the coast, taking mostly fish, including waste from the fishing industry, and cephalopods. It will also consume small mammals, arthropods, small birds and plant material (9).
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Description

With typical gull colouring of black, white and grey, Audouin's gull's most distinctive features are its scarlet red bill and dark eye. The head and body are white, the wings are grey, and the tail is black. In flight black wedges are revealed on the forewing, aiding identification. This gull species looks similar to the yellow-legged gull (Larus michahellis), but greyish-black legs distinguish Audouin's gull. Juveniles have a brown head that fades to white with age (7).
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Distribution

Range Description

Larus audouinii breeds in (all data for pairs) Spain (19,517 [Gutiérrez and Guinart 2008]), mainly the Chafarinas Islands and the Ebro Delta with the latter holding 67% of the global population (14,177 in 2007 [Gutiérrez and Guinart 2008]), Algeria (100-600), Greece (300-500 (D. Portolou in litt. 2010), and Sardinia and Tuscan Archipelago, Italy (1,019 [N. Baccetti in litt. 2008]), with smaller colonies in Portugal (11 [Gutiérrez and Guinart 2008]), Corsica, France (84 in 2009 [Recorbet and Culioli 2009]), Cyprus (c. 32 [Charalambidou and Gücel 2008]), islets and rocks in the southern Adriatic Sea near Korcula and Peljesac Peninsula, Croatia (65 in 5 colonies [Rubinic and Vrezec 2000]), Turkey (60-90 [G. Eken in litt. 1999]), Tunisia (70-115) and Morocco (50-300). It winters on the coast of North and West Africa from Libya west to Morocco and south to Mauritania, Gambia, Senegal and Gabon (Sanpera et al. 2007) and there is a small wintering population in the east Mediterranean along the Aegean coast of Turkey. The global population has been estimated at 21,161 pairs (Gutiérrez and Guinart 2008), and a recent assessment estimated the European population (encompassing over 90% of the global population) to be stable or increasing throughout (Barov and Derhé 2011). This represents a significant increase from an estimated population of 1,000 pairs in 1975 and is thought to be a result of the increased availability mainly of effectively protected areas during the 1980s, and secondly of discarded fish from the trawlers, particularly around the Ebro Delta (Criado 1997) where the colony has grown rapidly since 1981 (Guitiérrez and Guinart 2008). The large expansion of Larus audouinii in the western Mediterranean has probably caused the breeding population in other parts of the Mediterranean to increase and new colonies have been found in Croatia and even out of the Mediterranean in southern Portugal (BirdLife International 2004; Onmus 2006). Nevertheless more than 90% of the European breeding population occurs at just four sites and only a single site (the Ebro Delta) held 67% of the global breeding numbers in 2007. Recruitment can be extremely rapid when food availability is high, resulting in high population growth rates (Tavecchia et al. 2007; Oro and Pradel 2000). It is a long-lived species with high adult survival and relatively low fertility. Adult annual survival is estimated at 0.95 (Tavecchia et al. 2007; Oro et al. 1999, 2004).

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Range

Mediterranean basin; winters to Senegambia.

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Range

The only gull that is limited to the Mediterranean (2), Audouin's gull breeds mainly in Spain, Algeria, Greece and Italy. It has less significant breeding colonies in France, Cyprus, Croatia, Turkey, Tunisia and Morocco. Flying south at the end of the breeding season, Audouin's gull spends the winter on the coast of north and west Africa. Its population has risen from just 1,000 pairs in 1975 to over 19,000 pairs today, following an increase in discarded fish waste from the fishing industry, particularly at the Ebro delta in Spain (8).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Behaviour Audouin's Gull is a medium sized gull largely restricted to the Mediterranean. It is partially migratory and dispersive (del Hoyo et al. 1996). It breeds in large monospecific colonies ranging from 10 up to 10,000 pairs (del Hoyo et al. 1996) at a density of up to 1 nest/ sq. m (del Hoyo et al. 1996). Egg-laying takes place in the second half of April until the beginning of May, and peak hatching occurs in late May (del Hoyo et al. 1996), 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 colony (Mañosa et al. 2004). After breeding the birds disperse widely around the Mediterranean coast (Sanpera et al. 2007; del Hoyo et al. 1996). Almost all juveniles and some adults migrate past Gibraltar during July-October (Olsen and Larsson 2003), peaking in August (Guitiérrez and Guinart 2008), to winter on the North African coast (del Hoyo et al. 1996). During the winter it roosts in flocks of several thousand (Olsen and Larsson 2003). It returns to its breeding sites between late February and mid April (del Hoyo et al. 1996). First year birds remain in the non-breeding range throughout the summer (Cramp and Simmons 1983), while most third-summer birds attend the breeding colony as non-breeders (Gutiérrez and Guinart 2008). Second-summer birds migrate to the Mediterranean but do not join the colony, instead forming large gatherings, often far from colonies (Gutiérrez and Guinart 2008). 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 sites (Tavecchia et al. 2007). 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 timetable (Mañosa et al. 2004). The species scavenges around fishing vessels, and uses discards extensively and very efficiently (Mañosa et al. 2004). The species's association with fisheries is more pronounced in the western than in the central and eastern Mediterranean (Pedrocchi et al.2002). A trawler moratorium off the Ebro Delta established in 1991 reduced food availability to birds and impacted breeding success, possibly by increasing foraging ranges (Arcos and Oro 1996). Habitat Breeding Colonies are located on exposed rocky cliffs and on offshore islands or islets (Cramp and Simmons 1983), normally not more than 50 m above sea level (Cramp and Simmons 1983). The Ebro delta colony is located on saltmarsh and a sandy peninsula (Olsen and Larsson 2003). 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 lentiscus (Cramp and Simmons 1983). 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 0-90o. 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 margins (Cramp and Simmons 1983). 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 floods (Cramp and Simmons 1983). It is a coastal species, rarely occurring inland and generally not travelling far offshore (Cramp and Simmons 1983). 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 patterns (Mañosa et al. 2004) and of commercial fishing by purse-seine netting (Pedrocchi et al.2002). It is also known to take some aquatic and terrestrial invertebrates, small birds and plant material such as the peanut Arachis, olive Olea, and grain (Cramp and Simmons 1983). The Ebro delta colony feeds largely on fish waste dumped by boats fishing nearby (Oro and Martínez-Vilalta 1992). The species is also known to feed on food discarded at tourist beaches (Cramp and Simmons 1983), and during a moratorium on trawling, it was found to forage in marshes, rice fields and occasionally at refuse tips (Mañosa et al. 2004; del Hoyo et al. 1996). They began to exploit the introduced North American Red Swamp Crayfish Procambarus clarkia, which are abundant in rice fields around the delta (Gutiérrez and Guinart 2008). Hence Ebro Delta birds have developed from being mainly pelagic foragers to more coastal-foraging, even scavenging species (Gutiérrez and Guinart 2008). The fishing mortatorium was relaxed in 2000 during the birds breeding season, and as discards became available, so the population was boosted once again (Gutiérrez and Guinart 2008). Diet during the breeding season has been found to vary between colonies due to fishing practices that target different species in the respective areas (Pedrocchi et al.2002). Breeding site The nests is a shallow scrape lined with available debris and vegetation (Cramp and Simmons 1983). It is placed among rocks and vegetation (del Hoyo et al. 1996). Foraging range During the non-breeding season, surveys in Morocco found birds no further than 46 km from the coast (Hoogendoorn and Mackrill 1987), and generally <40 km from the colony seems to be the norm (Mañosa et al. 2004). However, the maximum recorded foraging range from a colony was 160 km (Mañosa et al. 2004). In recent years, some birds have remained at the Ebro Delta colony over-winter, with an average of c. 90 birds during 1996-2008, but occasionally up to 300 birds (Gutiérrez and Guinart 2008). 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 narrower (SEO/BirdLife in litt. 2010). Juveniles tend to forage in upwelling zones, whereas subadults and adults are more independent of these sites (Martinez-Abrain et al 2002). It remains extremely rare along the northern coast of Spain (Gutiérrez and Guinart 2008).


Systems
  • Terrestrial
  • Marine
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Depth range based on 117 specimens in 1 taxon.
Water temperature and chemistry ranges based on 32 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 18.347 - 18.963
  Nitrate (umol/L): 0.996 - 2.642
  Salinity (PPS): 36.417 - 37.431
  Oxygen (ml/l): 5.032 - 5.437
  Phosphate (umol/l): 0.068 - 0.193
  Silicate (umol/l): 1.178 - 3.508

Graphical representation

Temperature range (°C): 18.347 - 18.963

Nitrate (umol/L): 0.996 - 2.642

Salinity (PPS): 36.417 - 37.431

Oxygen (ml/l): 5.032 - 5.437

Phosphate (umol/l): 0.068 - 0.193

Silicate (umol/l): 1.178 - 3.508
 
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The majority of colonies base themselves on rocky cliffs and islands with medium vegetation cover to provide shelter for chicks, however, the Ebro delta colony inhabits salt marsh and sandy seashore. Unlike many other species of gull, Audouin's gull is not pelagic, preferring to feed along the coastline (9).
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Life History and Behavior

Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 20.9 years (wild) Observations: Maximum longevity from banding studies is 20.9 years (http://www.euring.org/data_and_codes/longevity.htm).
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
NT
Near Threatened

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s
Arcos, J., Carboneras, C., Eken, G., Omnus, O., Oro, D., Papaconstantinou, C., Anderson, O., Portolou, D. & Baccetti, N.

Justification
This species may undergo a moderately rapid population decline in future if current fishery practices change and as such it is precautionarily treated as Near Threatened.

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Status in Egypt

Regular passage visitor?

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Status

Audouin's gull is classified as Near Threatened (NT) on the IUCN Red List (1) and is listed on Appendices I and II of the Convention on Migratory Species (CMS or Bonn Convention) (3). It is also listed on Appendix II of the Berne Convention on the Conservation of European Wildlife and Natural Habitats (4), Annex I of the EU Birds Directive (5), and Annex 2 of the African-Eurasian Migratory Water Bird Agreement (6). It is classified as endangered on the Greek Red Book of Threatened Vertebrates (2).
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Population

Population
Gutiérrez and Guinart (2008) reported a global population of 21,161 pairs. However, more recent figures point to a total of 21,300-22,300 pairs, of which 21,080-21,310 pairs are in Europe. The global population is therefore estimated to number 63,900-66,900 individuals (G. Eken in litt. 1999, N. Baccetti in litt. 2008, D. Portolou in litt. 2010).

Population Trend
Stable
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Threats

Major Threats
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 (Oro et al. 2004, Tavecchia et al. 2007, Barov and Derhé 2011). 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-farming (Arcos et al. 2006). Other important threats include coastal tourism developments, regulation of the river Ebro, mortality due to entanglement in fishing gear (mainly longlines and sporting lines) (Cooper et al. 2003; Belda and Sánchez 2000), and predation by terrestrial predators, such as red fox Vulpes vulpes, badger Meles meles and domestic dogs (Tavecchia et al. 2007; Oro et al. 1999). Predation by sympatric Yellow-legged Gull L. michahellis can be high at some breeding colonies, especially when densities of Audouin's Gulls are low (Bonaccorsi 2003; Travichon 2004; Oro et al. 2006; Paracuellos and Nevado 2010). Predation on chicks by black rats Rattus rattus has a negative impact at some breeding colonies (Jones et al. 2008). 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 (Oro and Matínez-Abraín 2007; Genovart et al. 2003; Martínez-Abraín et al. 2003). Peregrines Falco peregrinus, other raptors, some herons and snakes can also prey on adults and nests but only accidentally and locally (Oro 1997, 1996). Very high levels of mercury and other pollutants are found in this species (Sanpera et al. 2007), partly due to the consumption of discards (Arcos et al. 2002), 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 (Oro and Ruxton 2001; Oro et al. 2004).

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This gull species thrives on human practices of waste fish dumping. The population of Audouin's gull has risen spectacularly since the fishing industry, particularly in the Ebro delta of Spain, began dumping large volumes of fish waste overboard. Having adapted to this food source, Audouin's gull populations would now be decimated should the fishing industry choose to use the fish waste as animal food (9). In periods when the fisheries do not operate, Audouin's gulls have been seen to suffer food shortages, as well as becoming prey for the yellow-legged gull (Larus michahellis) (10). Audouin's gull is also threatened by tourism, which causes both increased coastal development and increased disturbance during the breeding season (8). Bird-watching and research activities have also been known to negatively impact on Audouin's gull (9). Predation by the red fox and the domestic dog, as well as by other gulls and peregrine falcons is increasing, but is only a minor threat (8).
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Management

Conservation Actions

Conservation Actions
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 colonies (Jones et al. 2008). Culling of Yellow-legged Gulls Larus michehellis was conducted from 2000 to 2009 on Alborán Island, Spain, and demonstrated immediate local benefits (Paracuellos and Nevado 2010). However, even in small, remote colonies, culling needs to be continuous to avoid a return to the original situation (Paracuellos and Nevado 2010).

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.

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Conservation

Audouin's gull has both a European and an International action plan for its survival. They aim to encourage the implementation of coastal habitat management plans for all Mediterranean countries, as well as calling for the designation of key sites as protected areas. Preventing habitat alteration at breeding sites and reducing disturbance are important. Crucially, the effects of fishing industry practices on Audouin's gull are to be monitored (9).
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Wikipedia

Audouin's Gull

The Audouin's gull (Ichthyaetus audouinii) is a large gull restricted to the Mediterranean and the western coast of Saharan Africa. It breeds on small islands colonially or alone, laying 2-3 eggs on a ground nest. As is the case with many gulls, it has traditionally been placed in the genus Larus.

In the late 1960s, this was one of the World's rarest gulls, with a population of only 1,000 pairs. It has established new colonies, but remains rare with a population of about 10,000 pairs.

This species, unlike many large gulls, rarely scavenges, but is a specialist fish eater, and is therefore strictly coastal and pelagic. This bird will feed at night, often well out to sea, but also slowly patrols close into beaches, occasionally dangling its legs to increase drag.

The adult basically resembles a small European herring gull, the most noticeable differences being the short stubby red bill and "string of pearls" white wing primary tips, rather than the large "mirrors" of some other species. The legs are grey-green. It takes four years to reach adult plumage.

This species shows little tendency to wander from its breeding areas, but there were single records in the Netherlands and England in May 2003.

This bird is named after the French naturalist Jean Victoire Audouin.

The Audouin's gull is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

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