Archived 2018 topic: Great Black-backed Gull (Larus marinus): uplist to Near Threatened or Vulnerable?

This discussion was first published as part of the 2017 Red List update. At the time a decision regarding its status was pended, but to enable potential reassessment of the species as part of the 2018 Red List update this post was kept open. A decision has now been made and this topic is now closed.

Great Black-backed Gull (Larus marinus) is currently considered Least Concern on the basis that it was not thought to approach the thresholds for Vulnerable under any of the Red List criteria. It has a very large, trans-Atlantic distribution, being found from the Great Lakes, U.S.A. and the east coast of U.S.A. and Canada, coastal Greenland, Iceland, Faroe Islands, Svalbard, U.K., Republic of Ireland, the west coast of mainland Europe, Scandinavia, Estonia and coastal European Russia. The population size is also large, with 118,000-133,000 pairs estimated in Europe alone. Therefore, the species would still not qualify for any category other than Least Concern under criteria B, C or D.

The species may, however, now be suffering a significant decline. Using data from the European Red List of birds (BirdLife International 2015), information provided by A. Bond in litt. (2016) and information from Hario and Rintala (2016), Wilhem et al. (2016), Bond et al. (2016), Ronconi et al. (2016), Washburn et al. (2016) and Mittelhauser et al. (2016) it has been calculated that this species is currently declining overall at a rate of 30-35% over a 3 generation period (36 years). Therefore, the species would seem to warrant listing as Vulnerable under criteria A2+3+4.

However, the causes of these declines are not certain. Several threats have been identified, including; collision with offshore windfarms (Bradbury et al. 2014); coastal oil spills and other kinds of pollution (BirdLife International 2015), although organochlorine contaminants do not appear to have an effect on chick condition and reproductive output in this species (Pekarik et al 2016); and the species may be caught as bycatch in fisheries (Anderson et al. 2011, Žydelis et al. 2013) as well as being deliberately hunted (Bregnballe et al. 2006). Reduced prey availability may also be impacting this species, with moratoria on certain types of fishing, and changes in fishery target species meaning that there may be reduced discard and hence less available prey (Boertmann and Frederiksen 2016, Mittelhauser et al. 2016, Wilhelm et al. 2016). Landfill closure could lead to further loss of potential foraging sites (Mittelhauser et al. 2016). In North America, increased predation rates by mammals and large birds of prey such as Bald Eagles, Haliaeetus leucocephalus, may be an additional threat (Mittelhauser et al. 2016); and on Sable Island in particular it has been suggested that gull declines on the island may be in part due to habitat changes (Ronconi et al. 2016).

Historically the species underwent a marked population increase and range expansion southwards between the 1930s and 1975, as well as spreading north to Spitsbergen. In the Nearctic,  the breeding range has also extended southwards considerably since mid-20th century; it first bred in Maine in 1928, Massachusetts in 1931, New York in 1940, the Great Lakes in 1954, and New Jersey in 1966. In New England the population increased from 30 pairs in 1930 to 12,400 in 1972 (Burger et al. 2017).

It is possible therefore that the subsequent declines documented above represent an adjustment to previous lower levels following a human-mediated increase, and could be considered to form part of a long-term fluctuation (as previously discussed for European Herring Gull in 2015). It may therefore be appropriate to consider listing the species as Near Threatened although the raw data suggest listing as Vulnerable.Were this to be the case, the population should continue to be monitored closely and were it to show no sign of stabilisation it should then be listed in a higher threat category.

We would therefore welcome any comments and further information regarding this proposed uplisting, particularly around the likely drivers of the recent decline. This will help us to determine whether the species warrants uplisting to Near Threatened or Vulnerable under criterion A2abcde+3bcde+A4abcd.

References

Anderson, O.R.J., Small, C.J., Croxall, J.P., Dunn, E.K., Sullivan, B.J., Yates, O. and Black, A. 2011. Global seabird bycatch in longline fisheries. Endangered Species Research 14: 91-106.

BirdLife International. 2015. European Red List of Birds. Office for Official Publications of the European Communities, Luxembourg.

Boertmann, D.; Frederiksen, M. 2016. Status of Greenland populations of Great Black-backed Gull (Larus marinus), Lesser Black-backed Gull (Larus fuscus) and Herring Gull (Larus argentatus). Waterbirds 39(sp1): 29-35.

Bond, A. L.; Wilhelm, S. I.; Robertson, G. J.; Avery-Gomm, S. 2016. Differential declines among nesting habitats of breeding Herring Gulls (Larus argentatus) and Great Black-backed Gulls (Larus marinus) in Witless Bay, Newfoundland and Labrador; Canada. Waterbirds 39(sp1): 143-151.

Bradbury, G., Trinder, M., Furness, B., Banks, A.N., Caldow, R.W.G. and Hume, D. 2014. Mapping Seabird Sensitivity to Offshore Wind Farms. PLoS ONE 9(9): e106366.

Bregnballe, T.; Noer, H.; Christensen, T.K.; Clausen, P.; Asferg, T.; Fox, A.D.; Delany, S. 2006. Sustainable hunting of migratory waterbirds: the Danish approach. In: G. Boere, C. Galbraith and D. Stroud (eds), Waterbirds around the world, pp. 854-860. The Stationery Office, Edinburgh, U.K.

Burger, J., Gochfeld, M., Kirwan, G.M., Christie, D.A. & Garcia, E.F.J. (2017). Great Black-backed Gull (Larus marinus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/53974 on 1 June 2017).

Hario, M.; Rintala, J. 2016. Population trends in Herring Gulls (Larus argentatus), Great Black-backed Gulls (Larus marinus) and Lesser Black-backed Gulls (Larus fuscus fuscus) in Finland. Waterbirds 39(sp1): 10-14.

Mittelhauser, G. H.; Allen, R. B.; Chalfant, J.; Schauffer, R. P.; Welch, L. J. 2016. Trends in the nesting population of Herring Gulls (Larus argentatus) and Great Black-backed Gulls (Larus marinus) in Maine, USA, 1977-2013. Waterbirds 39(sp1): 57-67.

Pekarik, C.; Barker, I. K.; Weseloh, D. V. C. 2016. Organochlorine contaminants, immunocompetence, and vitellogenin in Herring Gulls (Larus argentatus) and Great Black-backed Gulls (Larus marinus) nesting on Lake Ontario in 2001-2002. Waterbirds 39(sp1): 180-201.

Ronconi, R. A.; Stephens, J. R.; Crysler, Z. J.; Pollet, I. L.; Fife, D. T.; Horn, A. G.; Taylor, P. D. 2016. Distribution, abundance and trends of gulls and terns breeding on Sable Island, Nova Scotia, Canada. Waterbirds 39(sp1): 44-56.

Washburn, B. E.; Elbin, S. B.; Davis, C. 2016. Historical and current trends of Herring Gulls (Larus argentatus) and Great Black-backed Gulls (Larus marinus) in the New York Bight, USA. Waterbirds 39(sp1): 74-86.

Wetlands International (2012) Waterbird Population Estimates. 5th edition. http://wpe.wetlands.org/bundles/voidwalkerswpe/images/wpe5.xls

Wilhelm, S. I.; Rail, J.-F.; Regular, P. M.; Gjerdrum, C.; Robertson, G. J. 2016. Large-scale changes in abundance of breeding Herring Gulls (Larus argentatus) and Great Black-backed Gulls (Larus marinus) relative to reduced fishing activities in southeastern Canada. Waterbirds 39(sp1): 136-142.

Žydelis, R.; Small, C.; French, G. 2013. The incidental catch of seabirds in gillnet fisheries: A global review. Biological Conservation 162: 76-88.

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6 Responses to Archived 2018 topic: Great Black-backed Gull (Larus marinus): uplist to Near Threatened or Vulnerable?

  1. If the current population size is still around the one three generations before, I would suggest waiting with the uplisting to Near Threatened. Keeping a population under watch does not require having it listed in any of the threatened or near threatened categories but such a move would trigger conservation measures such as listing the relevant populations on Column A of AEWA and designating key sites. None of these would be justified if a species, whose increase was facilitated by discard and rubbish damps, returns to a lower population level, i.e. the same approach as in case of the European Herring Gull could be followed.

  2. Andy Symes (BirdLife) says:

    Preliminary proposals

    Based on available information, our proposal for the 2017 Red List would be to pend the decision on this species and keep this discussion open until 2018, while leaving the current Red List category unchanged in the 2017 update.

    There is now a period for further comments until the final deadline of 4 August, after which the recommended categorisations will be put forward to IUCN.

    Final 2017 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  3. James Westrip (BirdLife) says:

    Tim Meehan has kindly provided analyses of Christmas Bird Count data. Taken from long-term trends (1966-2017), these data suggest an annual decline of 0.97% (4.69% annual decline to 0.52% annual increase) in this species. This would equate to a reduction of 29.72% (82.27% reduction to 20.43% increase) over three generations.

  4. Rob Martin (BirdLife International) says:

    In support of the supposition that declines in some northern European countries are relatively short-term adjustments, recent trend estimates for the UK indicate that over the past 36 years (three generations) overall declines are of a far smaller magnitude than between 2000 and 2012 (http://jncc.defra.gov.uk/page-2888). Similarly, while the trend in Sweden between 2001 and 2011 was an estimated as a decline of between 20-50%, the long term (1980-2011 trend was stable): the population increased to the 1990s, then stabilised prior to the decline.
    Using the trend that most closely matches the three generation length reduces the estimate of the current rate of decline to 23.6%. Given that the short-term declines do not appear to be continuing in the UK, the species may be best kept as Least Concern at present. The current comprehensive seabird census in the UK will provide greater accuracy to guide the assessment, as will the reporting round on the status of Europe’s birds in the next two years.

  5. Rob Martin (BirdLife International) says:

    Based on the available information, our preliminary proposal for the 2018 Red List would be to close this topic and retain the species as Least Concern for now, pending any further information regarding current trends.

    There is now a period for further comments until the final deadline in mid-July, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.

    The final 2018 Red List categories will be posted on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  6. Nele Markones says:

    Sorry for the late posting, I just wanted to add a quick overview of the situation at sea that gives additional information on the general development of the population and on the potential drivers:
    In the German offshore areas, the numbers of GBBG at sea have declined by more than 90% (German North Sea: 99%, data from 1990-2013, summer; German Baltic Sea: 93%, data from 2000-2014, winter; source: German at-sea monitoring report, Markones et al. 2015). Strongest decrease took place around the turn of the millennium. Steep declines in numbers at sea both in the breeding and non-breeding period are also observed at the scale of the whole North Sea (ESAS data, Garthe et al. in prep.). Results indicate that declines along the British East coast are even more severe than in the southern North Sea.
    Since those massive declines at sea are not mirrored by analogous trends at the breeding sites, they will result from shifts in distribution / habitat use and a substantial diminishment of the importance of marine food sources for GBBG in the North Sea and probably also Baltic Sea region.

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