LC
European Herring Gull Larus argentatus



Justification

Justification of Red List category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). Despite the fact that the population trend appears to be decreasing, the decline is not currently believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). For these reasons the species is evaluated as Least Concern.

Population justification
The breeding population is estimated to number 531,000-608,000 pairs, which equates to approximately 1,060,000-1,220,000 mature individuals and 1,590,000-1,830,000 individuals (BirdLife International in prep.).

Trend justification
This species is endemic to Europe where there are well-established monitoring schemes that include the species (Keller et al. 2020, JNCC 2021, BirdLife International in prep.). This monitoring data, collated for all range states has reported an overall rapid decline in the order of 37% over the equivalent of the past three generations (BirdLife International in prep.). However, trends within the two countries holding the majority of the breeding population, Norway and the UK have low confidence, to the extent that the conservation status of the species in the UK was recently considered data deficient based on the same data (Stanbury et al. 2017). While long-occupied coastal colonies are considered well-monitored, data for the inland population is less certain and these colonies have increased rapidly (Mitchell et al. 2004, Keller et al. 2020). The reporting of Seabird 2000 (Mitchell et al. 2004) included estimates for Great Britain and Ireland for both natural and roof-nesting birds. At that time the numbers of the latter were growing at an annual rate of nearly 14% (Mitchell et al. 2004). If both the rate of decrease in the 'natural' nesting population and increase in the roof-nesting population continued at these rates, the population would have nearly doubled overall by 2021. As such, the lack of monitoring within urban areas where gulls have expanded their range, and so data from coastal communities may not be reflective of the global population (J. Coulson in litt. 2021). 

Further large uncertainty is present in the numbers reported for Norway. Limited count data has been collected and numbers reported are based on extrapolations of estimated trends from a small number of colonies. Consequently the two values that could be used for deriving a rate of reduction, 233,000 pairs assigned to 2005 (Barrett et al. 2006) and 72,000 pairs (Anker-Nilssen et al. 2015) are values based on extrapolations of much of the same count data with different modelled trends derived from a small percentage of the breeding population (Fauchald et al. 2015). Fauchald et al. (2015) record that the latest counts were from 1983 for the Norwegian Sea, 2005 for the Barents Sea and 1986 (for both North Sea and Skagerrak). It appears that a considerable extrapolation was used to generate the values given for 2005: the numbers for the most recent counts were 16,620 pairs for North Sea and Skagerrak (from 1986), 41,553 pairs for Norwegian Sea (1983) and 33,631 pairs for Barents Sea (2005), totalling 91,444 pairs for a timeframe that spans 22 years. Modelled populations using measured demographic parameters have been subsequently used to generate predictions of the population trends, but the relevant confidence to assign to these is unclear, and resurveys of large colonies are needed.

Both the UK and Norway data hint at a likely population reduction over the past three generations, which may have been at a moderate or rapid rate. Data for Sweden also indicate a very rapid decline (equivalent to 72% over three generations, although slowing recently [BirdLife International in prep.), but this is thought to have been offset by birds switching colonies to Denmark, which has seen a 174% increase over the same period. But reductions are also noted for the Netherlands, Finland, Estonia, Germany, Ireland and France and while the larger population sizes in the UK and Norway result in much uncertainty in the trend, a suspected overall population reduction of between 1-19% over the past three generations is considered to be the most likely range of the current trend.
 
The species's population increased and the distribution expanded in many range states and overall during the 20th century (Tucker and Heath 1994, BirdLife International 2004, Weseloh et al. 2020). Around the turn of the century, declines began in several key countries, including Norway (Fauchald et al. 2015) and the UK (JNCC 2020). The decline appears to be partly linked to waste management and reduced fishery discards, and so the species's population may be readjusting to a lower level similar to that before it was able to take advantage of anthropogenic and unsustainable food sources. Population declines may be particularly attributed to low recruitment, as juveniles are especially reliant on waste and fishery discards (V. Dierschke in litt. 2021).

Distribution and population

Herring Gulls breed from Iceland, the British Isles and France through northwest Europe to northwest Russia, and northern Siberia east to the Bering Strait. Most notable breeding areas include the United Kingdom, Denmark, Norway, Sweden, France, the Netherlands and Russia. It possibly breeds in Svalbard (Weseloh et al. 2020). Northern breeding populations of this species are migratory (del Hoyo et al. 1996) whereas populations in the south are nomadic or completely non-migratory (Flint et al. 1984). Northern populations winter mainly in maritime northwest Europe (Cramp and Simmons 1983, Calladine 2002), but as far south as northern Iberia (Weseloh et al. 2020).  

Ecology

The species inhabits coastal and near-coastal areas but may also forage inland on large lakes and reservoirs, fields and refuse dumps (del Hoyo et al. 1996). It has no specific breeding habitat (del Hoyo et al. 1996) but may show a preference for rocky shores with cliffs, outlying stacks or islets (del Hoyo et al. 1996, Snow and Perrins 1998), otherwise nesting on rocky and grassy islands, sandy beaches (del Hoyo et al.1996), dunes (Richards 1990), gravel bars, saltmarshes, rocky outcrops, buildings, claypits (del Hoyo et al. 1996), tundra with reeds or hummocks (Flint et al. 1984), swampy lowlands near lakes and on river islands (Flint et al.1984). When inland on migration the species also shows a preference for large river valleys (Flint et al. 1984). Although Herring Gulls exploit refuse tips and farmland extensively all year round, their breeding distribution is extremely coastal compared to other Larus gulls (other than L. marinus) (Gibbons et al. 1993). O'Hanlon et al. (2018) found that colonies were larger when associated with sheltered coastlines and farmland, believed to be due to the greater variety and availability of food. 

The species has a highly opportunistic diet and will exploit almost any superabundant source of food (del Hoyo et al. 1996). It takes fish, earthworms, crabs and other marine invertebrates (e.g. molluscs, starfish or marine worms), adult birds, bird eggs and young, rodents, insects (e.g. ants), berries and tubers (e.g. turnips) (del Hoyo et al. 1996). It also scavenges at refuse dumps, fishing wharves and sewage outfall zones and frequently follows fishing boats (del Hoyo et al. 1996, Huppop and Wurm 2000). The feeding range has been variously reported as 35 km (for breeding herring gulls in a Dutch colony) (Spaans 1971), 41 km (in Westphalia, Germany, outside the breeding season) (Sell and Vogt 1986), 50 km (for breeding birds in Morocco) (Witt et al. 1981) and 70 to 100 km (for herring gulls breeding in Denmark) (Klein 1994). Several other studies have reported shorter foraging distances (Witt et al. 1981, Cramp and Simmons 1983, Sibley and McCleery 1983, Nogales et al. 1995, Pons and Migot 1995, BirdLife International 2000). Refuse tips are frequently exploited by foraging individuals (Sibley and McCleery 1983, Nogales et al. 1995, Pons and Migot 1995) and so the feeding distribution of some colonies will be determined by location of refuse dumps (BirdLife International 2000). On the basis of a simple density model of birds at sea, it has been estimated that 95% of herring gulls breeding on Terschelling in the Dutch Wadden Sea foraged within 54 km of the colony (BirdLife International 2000).
Northern breeding populations of this species are migratory (del Hoyo et al. 1996) although populations in the south are nomadic or completely non-migratory (Flint et al. 1984). Outside of the breeding season the species is highly gregarious and gathers in large flocks in favoured sites (Richards 1990, Snow and Perrins 1998). Individuals show foraging site fidelity (Shamoun-Baranes and van Loon 2006)

Threats

The species is at risk from reductions in food supplies due to changes in fishing practices. Reduction in discards has greatly reduced available food in parts of the species range that had seen rapid increases in the previous century. Further, trophic shifts have impacted fishing activity and catch size, which appears to be directly related to colony reproductive success: lower catches are resulting in lower breeding success and the decline of colonies in the UK (Foster et al. 2017). Changes to land-fill management across northern Europe may be detrimental to winter survival of Herring Gulls (Olsson et al. 2017, Shlepr et al. 2021). 

The species is also vulnerable to collisions with wind turbines (Bradbury et al. 2014) and was the most frequently recorded casualty in a study of 4.7 km of the English coastline over 11 years (Newton and Little 2009). 

In the past, persecution has represented a significant source of mortality however, the EU directive (2009/147/EC) has made it an offense to kill birds or destroy eggs without license. This has likely resulted in a reduction in mortality due to persecution, however, there is still some level of culling, with 5,000 birds culled under license 2010-12 in the UK (Coulson 2015). The threat is unlikely to disappear, with a recent paper calling for lethal controls for closely related Larus spp. in Gulf of Maine (Scopel and Diamond 2017) however, this is thought to cause negligible declines. 

The European Herring Gull, among other gulls, is currently at low risk of plastic ingestion in the Arctic, although southern populations have variable levels of plastic ingestion from the proximity to anthropogenic sources of pollution. The risk of plastic ingestion may increase as the human population, shipping and fishing activity increase in the Arctic region (Baak et al. 2021).

The species is threatened by coastal oil pollution (Gorski et al. 1977) and is susceptible to avian influenza and so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006). Botulism reports have been increasing in Britain in the last 45 years and, despite the number of deaths not having been quantified, it is suggested to have been a factor in the population declines in Britain (Coulson 2015). It is vulnerable to being caught as bycatch in fisheries, including longlines, trawls and gillnets (Anderson et al. 2011, Zydelis et al. 2013).

Conservation actions

Conservation Actions Underway
The species is covered by the African Eurasian Waterbird Agreement. In the EU it is listed under Annex II of the Birds Directive. Gulls and their eggs and nests are protected under the WildLife and Countryside Act, UK, and is a priority in the UK Biodiversity Action Plan

Conservation Actions Proposed
On-board monitoring programmes for seabird bycatch in fishing vessels, and implementation of mitigation measures where appropriate. Increased understanding of movements to assist placement of offshore wind farms. Establish long-term monitoring programmes across the Arctic to track plastic ingestion, or have plastic research incorporated into current programmes.

Acknowledgements

Text account compilers
Martin, R., McGonigle, K., Hermes, C.

Contributors
Ashpole, J, Baccetti, N., Bourne, W.R.P., Butchart, S., Calvert, R., Coulson, J., Dierschke, V., Ekstrom, J., Hatchett, J., Hibble, R., Lehtiniemi, T., Malpas, L., Mischenko, A.L., Morkunas, J., Petkov, N., Raudonikis, L., Steiof, K., Stuart, A., Symes, A., Taylor, J., Virkkala, R. & Yésou, P.


Recommended citation
BirdLife International (2024) Species factsheet: Larus argentatus. Downloaded from https://datazone.birdlife.org/species/factsheet/european-herring-gull-larus-argentatus on 29/02/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org on 29/02/2024.