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

This species breeds in (all data for pairs) Spain (19,461), mainly the Chafarinas Islands and the Ebro Delta with the latter holding 67% of the global population (14,177 in 2007 [Gutirrez and Guinart 2008]), Algeria (100-600), Greece (350-500), and Sardinia and Tuscan Archipelago, Italy (1,153-1,286), with smaller colonies in Portugal (400-460), Corsica, France (82), Cyprus (14-28), islets and rocks in the southern Adriatic Sea near Korcula and Peljesac Peninsula, Croatia (60-70), Turkey (47-90)(BirdLife International 2015),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 (Gutirrez 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 Derh 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 (Guitirrez and Guinart 2008). The large expansion of this speciesin 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 (Oro and Pradel 2000,Tavecchiaet al. 2007). It is a long-lived species with high adult survival and relatively low fertility. Adult annual survival is estimated at 0.95 (Oro et al. 1999, 2004,Tavecchiaet al. 2007).

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Range

Mediterranean basin; winters to Senegambia.
  • Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2014. The eBird/Clements checklist of birds of the world: Version 6.9. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/

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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
Colonies are located on exposed rocky cliffs and on offshore islands or islets, 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, eryngoEryngium, grass and low bushes ofPistacia 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.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).It 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 diurnal vertical (diel) migration patterns(Maosaet al. 2004) and of commercial fishing by purse-seine netting (Pedrocchiet al.2002). It is also known to take some aquatic and terrestrial invertebrates, small birds and plant material such as the peanutArachis, oliveOlea, and grain (Cramp and Simmons 1983). The Ebro delta colony feeds largely on fish waste dumped by boats fishing nearby (Oro and Martnez-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 (del Hoyoet al.1996,Maosaet al. 2004). They began to exploit the introduced North American Red Swamp CrayfishProcambarus clarkia, which are abundant in rice fields around the delta (Gutirrez and Guinart 2008). Hence Ebro Delta birds have developed from being mainly pelagic foragers to more coastal-foraging, even scavenging species (Gutirrez and Guinart 2008). The fishing moratorium was relaxed in 2000 during the breeding season, and as discards became available, so the population was boosted once again (Gutirrez 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 (Pedrocchiet al.2002).

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(Maosaet al. 2004). However, the maximum recorded foraging range from a colony was 160 km(Maosaet 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 (Gutirrez 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/BirdLifein 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 (Gutirrez and Guinart 2008).

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 one 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 (Maosa 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 (Guitirrez 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 (Gutirrez and Guinart 2008). Second-summer birds migrate to the Mediterranean but do not join the colony, instead forming large gatherings, often far from colonies (Gutirrez 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 (Maosa et al. 2004). The species scavenges around fishing vessels, and uses discards extensively and very efficiently (Maosa 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).


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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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
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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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
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2015

Assessor/s
BirdLife International

Reviewer/s
Symes, A.

Contributor/s
Arcos, J., Carboneras, C., Eken, G., Omnus, O., Oro, D., Papaconstantinou, C., Anderson, O., Portolou, D., Baccetti, N., Hellicar, M., Bourne, W. & Recorbet, B.

Justification
This species is not currently declining and is unlikely to decline sufficiently rapidly in the near future to be listed as Near Threatened. It is therefore treated as Least Concern.


History
  • 2012
    Near Threatened (NT)
  • Near Threatened (NT)
  • Near Threatened (NT)
  • Near Threatened (NT)
  • Near Threatened (NT)
  • Lower Risk/near threatened (LR/nt)
  • Lower Risk/conservation dependent (LR/cd)
  • Threatened (T)