The Convention for the Protection of the Marine Environment of the North-East Atlantic (the “OSPAR Convention”) was opened for signature at the Ministerial Meeting of the former Oslo and Paris Commissions in Paris on 22 September 1992. The Convention entered into force on 25 March 1998. It has been ratified by Belgium, Denmark, Finland, France, Germany, Iceland, Ireland, Luxembourg, Netherlands, Norway, Portugal, Sweden, Switzerland and the United Kingdom and approved by the European Community and Spain.

This background document on the Lesser black backed gull – Larus fuscus fuscus - has been developed by OSPAR following the inclusion of this species on the OSPAR List of threatened and/or declining species and habitats (OSPAR agreement 2008-6). The document provides a compilation of the reviews and assessments that have been prepared concerning this species since the agreement to include it in the OSPAR List in 2003. The original evaluation used to justify the inclusion of Larus fuscus fuscus in the OSPAR List is followed by an assessment of the most recent information on its status (distribution, population, condition) and key threats prepared during 2008-2009. Chapter 7 provides recommendations for the actions and measures that could be taken to improve the conservation status of the species. On the basis of these recommendations, OSPAR will continue its work to ensure the protection of Larus fuscus fuscus, where necessary in cooperation with other organisations. This document may be updated to reflect further developments.

Ecology and breeding biology

Larus fuscus fuscus is a migratory species, leaving the breeding areas from August to fly south to the Black Sea and the eastern part of the Mediterranean and Africa. Breeding colonies are often situated many kilometers inland, often on bogs or other flat areas or on small islands nearly always with rich dense vegetation. L. fuscus is a surface predator and feeds mainly on Atlanto-Scandic herring, Clupea harengus and sprat, Sprattus sprattus (Strann, 1992: In northern Norway, the species is a typical offshore feeder with a very limited terrestrial diet, and only infrequently feeds at rubbish dumps, although this has been reported in Finland to some extent.).

Original evaluation against the Texel-Faial criteria for which the species was included on the OSPAR List

The subspecies L.f.fuscus was nominated by one Contracting Party (Norway), and first listed by OSPAR 2003. The criteria cited were decline, rarity and sensitivity, with information also provided on threat.
Regional importance. At the time of listing, the total population of the fuscus subspecies was believed to be under 15 000 pairs, of which about 2500 pairs bred within the Barents Sea on the Norwegian and Russian coasts (Anker-Nilssen et al., 2000).
Decline. The ICES evaluation of this nomination (ICES, 2002) was based on compelling evidence of a decline in the numbers of L.f.fuscus, estimated at 90% since 1970. The evidence of a marked decline in breeding numbers of L.f.fuscus in northern Norway was considered very strong. The species was also reported to have disappeared from the Murman coast and the north-western White Sea of Russia (Anker-Nilssen et al., 2000).
Rarity. At the time of listing, the subspecies had a relatively small population and limited number of breeding sites, and was considered a rare sub-species in OSPAR Region I.
Sensitivity. L.f.fuscus was listed as sensitive due to the small numbers breeding at a very limited number of locations. It was considered to be particularly sensitive to disturbance, predation, and oil pollution.
Threats. The case report for this species cites the likely principal threats as man-made pollution such as PCBs, decline in prey species, and competition with and predation by the herring gull Larus argentatus.

Distribution in OSPAR maritime area

The species has a complicated systematics: 5 subspecies of L.fuscus have been described and the classification is widely accepted (ICES, 2002). The subspecies, L. fuscus fuscus breeds in Sweden and northern Norway across to the western part of the Kola Peninsula and the western White Sea and accidentally on Bjørnoya, and also in Estonia and in very small numbers in eastern Denmark (Strann, Semashko and Cherenkov, in Anker-Nilssen et al., 2000; Wetlands International, 2006; Thomas Bregnballe in litt. 2008). In Finland, the subspecies breeds through southern and central Finland but is a rare breeder in the north. Most of those breeding in Sweden, Finland and Denmark breed within the Baltic Sea basin and so originate outside the OSPAR area but some of these birds may move into OSPAR waters to feed or after breeding.

L.f.fuscus is a true long-distance migrant, using the East European – Black Sea migration flyway. A varying number stay in the eastern Mediterranean down to Ethiopia, but the bulk of the population flies to winter in the Great Lakes region of Kenya, Tanzania, and Uganda. In Uganda, the largest concentrations occur at Lake Victoria and the water bodies of the western (Albertine) Rift Valley, notably Queen Elizabeth National Park. Birds stay here from October - November to March - April, with groups of up to 500 - 700 birds occurring (Satellite tracking of a juvenile bird from a breeding area in Finland found that it travelled to Lake Victoria in 1 month (29 August to 29 September 1999), and made its final non-stop journey from the Nile delta to Lake Victoria, a distance of around 3 500 km, in 92 hours (average 38 km/h; Kube et al., 2000). A few birds also winter in south-west Asia (Wetlands International, 2006). Apart from a limited northward migration, immature birds remain in the wintering areas through the summer. The adults arrive on the breeding grounds in late May and early June (del Hoyo et al. 1996; Malling Olsen and Larsson, 2004).

Population (current/trends/future prospects)

The global population of L.fuscus (all subspecies) is put at 680 000 - 750 000 (BirdLife International 2008). The European breeding population is considered large (>300 000 pairs), with 5000 - 7000 pairs in Finland, 30 000 - 40 000 pairs in Norway, 4000 - 5700 pairs in European Russia, and 2000 - 5000 in Sweden and 4000 - 6000 pairs in Denmark, but these are for all subspecies and not exclusively L.f.fuscus (BirdLife International 2004). Recent national surveys resulted in estimate of 18 000 - 19 000 pairs (or 54 000 - 57 000 individuals) for the fuscus subspecies (Wetlands International, 2006).
The Norwegian population is put at c. 1300 pairs (Barrett et al. 2006), which represents 6 - 7% of the world population of L.f.fuscus. A national survey carried out in Finland in 2003, gave a total population estimate of 8300 pairs (BirdLife Finland), representing around 45% of the world population. Trends are difficult to analyse as early population estimates did not differentiate between subspecies and included intermedius in surveys in Denmark, southern Norway and Sweden in this population (Wetlands International, 2006).
Norway. Although no complete census was ever made, the population of the fuscus subspecies in the 1960s was probably at least 3000 - 4000 pairs (Haftorn, 1971) but had declined to around 1300 pairs by 2005 (comprising about 1000 pairs along the Norwegian Sea coast and 300 pairs in the Barents Sea region), and the fuscus subspecies is now considered extinct in the Lofoten Islands (Barrett et al., 2006). In colonies monitored in Nord-Trøndelag and Sør-Helgeland, declines of 5 - 10% p.a. have been recorded since 1980 and up to the mid-1990s. An increase in numbers was recorded for the first time in Helgeland (considered to be the core area for this subspecies along the Norwegian coast) between 1996 and 2005. An overall decline of 5.4%/year was reported by Barrett et al. (2006) over a 15 year period (1980 - 1995) at their study sites in northern Norway. By contrast, the population of the intermedius subspecies in Norway has increased greatly since the 1960s, when the population was estimated to be 5800 pairs (Barth, 1968). Monitoring has shown that despite large annual variations, this increase has continued at least in the Skagerrak region (area off Southern Norway between the Baltic and North Sea) at a rate of 1 - 5% p.a. since 1974. There seems to have been a reversal of this L.f.fuscus trend in recent years with numbers falling again at a rate of 4% p.a. No monitoring data for L. f. intermedius exist for the North Sea and Norwegian Sea coastlines.
Sweden. The L.fuscus population in Sweden has decreased from 17 000 breeding pairs in the seventies to 4000 - 5000 at its lowest point in the 1990s (Gärdenfors, 2005). A study in 2003 - 04 (Lif et al., 2005) showed that the L.f.fuscus had begun to recover from the decrease in the nineties but had, for unknown reasons, an unsustainable low breeding success. Survey results from 2006 estimated that there were over 8300 pairs of L.f.fuscus – showing a small increase since the 1990s (Axbrink, 2007).
Finland. The fuscus subspecies was also believed to have declined at a high rate (8%/year) in Finland between 1986 - 2002 (Hario et al., 1998; Anker-Nilssen et al., 2000; BirdLife International, 2004). However, based on a national survey in 2003, the population in Finland is thought to have decreased only slightly during the previous 10 years. In the inland areas, the population is probably stable, but the subspecies is still decreasing slightly in the south and in some areas on the west coast (Teemu Lehtiniemi in litt. 2008).
The cause(s) of the decline are unknown but may be related to food shortages during the breeding season or, as proposed for the Finnish population, high chick mortality caused by elevated levels of DDE in adults picked up in the wintering areas in East Africa (Strann and Vader, 1992; Anker-Nilssen et al., 2000; Bakken et al., 2003; Hario et al., 2004). There has also been a marked reduction in the population of the fuscus subspecies in neighbouring areas of Russia. The species no longer breeds along the Murman coast or the north-western part of the White Sea of Russia (it has declined in the northern part of Karelia since the 1920s and in the southern part since the 1950s), although it bred in a few colonies in Onezhski Bay in the southern part of the White Sea which showed an increase at least until the early 1990s when the population was estimated to be c.1600 pairs (Anker-Nilssen et al. 2000).

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