Appendix 1: Sources and references for vulnerability assessment
1.1 Evidence for exposure (references)
1.1.1 Current impacts attributed to climate change:
European Herring Gull 1 - Changes in mercury cycling (due to increased sea temperatures) has led to increased exposure to mercury, with associated impacts on herring gull health- Beldowska, M., et al. “Mercury concentration in the coastal zone of the Gulf of Gdansk as a function of changing climate—preliminary results.” Baltic Sea Science Congress: new horizons for Baltic Sea science. Klaipeda University CORPI, Klaipeda. Vol. 140. 2013. Overview of how climate change can lead to changes in mercury concentration in Baltic
- Beldowska, Magdalena, et al. “Macrophyta as a vector of contemporary and historical mercury from the marine environment to the trophic web.” Environmental Science and Pollution Research 22.7 (2015): 5228-5240. Overview of how mercury concentration in the Baltic cycles into seabird tissues and how it affects ecosystem health
- Saniewska, Dominika, et al. “Climate change and its impact on the mercury cycling in the southern Baltic Sea.” Ecosystem dynamics in the Baltic Sea in a climate change perspective, 03.2015. Conference Umeå, Sweden, 2015. Climate change is likely leading to increased mercury concentration cycling in the southern Baltic, this is leading to higher concentrations of mercury in herring gull tissues. While this has not been shown to be affecting the population in the Baltic, it is known that mercury poisoning can severely affect herring gull health.
- Luczak, Christophe, et al. “North Sea ecosystem change from swimming crabs to seagulls.” Biology letters 8.5 (2012): 821-824. Increased numbers of swimming crabs significantly correlate with sea surface temperature increases and changes in the abundance of lesser black-backed gulls at 21 major North Sea breeding colonies (across northern France and Belgium). Though note there is some debate on whether an increase in crabs is actually the cause of the population increase.
- Prop, Jouke, et al. “Climate change and the increasing impact of polar bears on bird populations.” Frontiers in Ecology and Evolution 3 (2015): 33. Polar bears are swapping prey due to lack of sea ice and predate more heavily on glaucous gulls (amongst other seabirds). In some years it severely affects reproductive success in Svalbard and Greenland
- Alava, Juan Jose, et al. “Climate change–contaminant interactions in marine food webs: Toward a conceptual framework.” Global change biology 23.10 (2017): 3984-4001. Potential exacerbation of POPs and mercury in marine food webs due to climate change (i.e., increasing temperatures). Glaucous gulls appear to have high accumulation of compounds, but there’s no established negative effect on populations. Study was conducted across their range, especially around Greenland.
- Galaktionov, K. V. “Patterns and processes influencing helminth parasites of Arctic coastal communities during climate change.” Journal of Helminthology 91.4 (2017): 387-408. Review of helminth parasites across the Arctic, especially in seabirds. Notes that several parasites have been recorded in species they have never been associated with before. Most likely because boreal crustaceans are shifting north, along with associated parasites. Notable species are glaucous gulls and black-legged kittiwakes which now have significant new parasites at rapidly increasing loads.
- Burthe, Sarah J., et al. “Assessing the vulnerability of the marine bird community in the western North Sea to climate change and other anthropogenic impacts.” Marine Ecology Progress Series 507 (2014): 277-295. Greater black-backed gull productivity decreases as sea surface temperature gets higher. Probably due to prey availability, study focusses on seabirds in Forth and Tay region.
- Gilg, Olivier, et al. “Living on the edge of a shrinking habitat: the ivory gull, Pagophila eburnea, an endangered sea-ice specialist.” Biology letters 12.11 (2016): 20160277. Demonstrates how closely linked Ivory gull ranges are to sea ice availability across its range, including Greenland, Svalbard, Russia and Canada. Also notes that their range is shrinking due to changes in sea ice
- Hamilton, Charmain D., et al. “Spatial overlap among an Arctic predator, prey and scavenger in the marginal ice zone.” Marine Ecology Progress Series 573 (2017): 45-59. Decreasing area of sea ice mean less area for Ivory gulls, polar bears and ringed seals (both of which commonly scavenge from). This leads to increased intra- and inter- specific competition.
- Sandvik, Hanno, et al. “The decline of Norwegian kittiwake populations: modelling the role of ocean warming.” Climate Research 60.2 (2014): 91-102. The study find a correlation between lower breeding success and sea surface temperature along Norwegian coast. The suggested mechanism is through prey availability as this is known to affect breeding success in various parts of their range.
- Vihtakari, Mikko, et al. “Black-legged kittiwakes as messengers of Atlantification in the Arctic.” Scientific Reports 8.1 (2018): 1-11. Kittiwake diet in Svalbard changed significantly over a 10-year period (2006-2016), from predominantly Arctic species to species more associated with warmer Atlantic waters, in correlation with increase in ocean temperature and loss of sea ice. There were, however, no significant changes in clutch size or breeding success during this time.
- Garðarsson, Arnþór, Guðmundur A. Guðmundsson, and Kristján Lilliendahl. “Framvinda íslenskra ritubyggða.” Bliki 32 (2013): 1-10. Kittiwakes have redistributed across Iceland. Populations in the north have decreased, and populations in the west have increased. The population in general is relatively stable. The authors hypothesise this is likely due to redistribution of capelin, a key prey species of kittiwakes in Iceland.
- Galaktionov, K. V. “Patterns and processes influencing helminth parasites of Arctic coastal communities during climate change.” Journal of Helminthology 91.4 (2017): 387-408. Review of helminth parasites across the Arctic, especially in seabirds. Notes that several parasites have been recorded in species they have never been associated with before. Most likely because boreal crustaceans are shifting north, along with associated parasites. Notable species are glaucous gulls and black-legged kittiwakes which now have significant new parasites at rapidly increasing loads.
- Burthe, Sarah J., et al. “Assessing the vulnerability of the marine bird community in the western North Sea to climate change and other anthropogenic impacts.” Marine Ecology Progress Series 507 (2014): 277-295. Kittiwake productivity decreases as sea surface temperature gets higher. Probably due to prey availability, study focusses on seabirds in Forth and Tay region.
- Calado, Joana G., et al. “Anthropogenic food resources, sardine decline and environmental conditions have triggered a dietary shift of an opportunistic seabird over the last 30 years on the northwest coast of Spain.” Regional Environmental Change 20.1 (2020): 1-13. Yellow-legged gulls have changed their diet following declines in sardine populations, driven by climate change and fishery activity. Study based on several populations on the north-west coast of Spain.
1.1.2 Change in European range size between present day and 2100:
Using a species distribution model (SDM) we correlated species occurrence during the breeding season with a number of terrestrial and marine environmental variables. Species range data came from the European Breeding Bird Atlas (EBBA2) database. Present-day and 2100 terrestrial data were downloaded from the WorldClim database. We used data from the MRI-ESM2 general circulation model (GCM), which is a high-performing model over Europe. Present-day and 2100 marine data were downloaded from the Bio-Oracle database which averages predictions of marine variables from several different atmospheric-oceanic general circulation models (AOGCMS; for full details see Assis et al., 2017). For the map presented in the summary we used representative concentration pathway (RCP) 4.5, which is an “intermediate” emissions scenario. All data were at 5-minute resolution.
- For European Herring Gull, Audouin’s Gull, Lesser Black-backed Gull, Glaucous Gull, Great Black-backed Gull, Ivory Gull, Black-legged Kittiwake, and Sabine’s Gull we included the following terrestrial variables: Mean temperature of the warmest month, precipitation during breeding season, isolation of landmass, area of landmass, distance to sea
- For Caspian Gull, and Yellow-legged Gull we included the following terrestrial variables: Mean temperature of the warmest month, precipitation during breeding season, distance to sea
- For Audouin’s Gull, Lesser Black-backed Gull, Glaucous Gull, Great Black-backed Gull, Ivory Gull, Black-legged Kittiwake, and Sabine’s Gull we included the following marine variables: Sea surface temperature (during the winter), salinity, maximum chlorophyll concentration, bathymetry (depth and variance)
Several other variables may strongly influence the distribution ofgullsand it is not possible to include all possible variables in a given model. However the following variables have previously been found to be important to predicting the distribution of gulls in Europe: sea level height. For local assessments of climate change, we recommend these variables are strongly considered. We hope to incorporate these variables into future versions of this guidance document.
After running our model we generated a present-day map where every grid-cell is given a habitat suitability score between 0 and 1, where 1 is very suitable habitat and 0 is not at all suitable. We then compared this with a corresponding map built with 2100 data, and highlighted currently inhabitated areas where 1) suitability drops sharply (i.e. by more than 0.1) and 2) suitability drops below a probability threshold set by the model. Conversely we also highlighted areas where suitability rose sharply and above a given threshold. While a drop in habitat suitability is likely to result in population declines, it is not a certainty, and it does not mean that a population will be extinct in 2100 or that a population is doomed to extinction. With conservation action and careful management, along with changes in human behaviour, such declines may be mitigated or in some cases prevented. For a full explanation of the model see the accompanying ‘Methodology’ document.
Underlying data were downloaded from:- Keller, V., Herrando, S., Voríšek, P., Franch, M., Kipson, M., Milanesi, P., Martí, D., Anton, M., Klvanová, A., Kalyakin, M.V., Bauer, H.-G. & Foppen, R.P.B. (2020). European Breeding Bird Atlas 2: Distribution, Abundance and Change. European Bird Census Council & Lynx Edicions, Barcelona. Source of range data
- Fick, S. E., & Hijmans, R. J. (2017). Worldclim 2: New 1-km spatial resolution climate surfaces for global land areas. International Journal of Climatology. http://worldclim.org/version2. Source of present-day and 2100 terrestrial data.
- Assis, J., Tyberghein, L., Bosch, S., Verbruggen, H., Serrão, E. A., & De Clerck, O. (2018). Bio-ORACLE v2.0: Extending marine data layers for bioclimatic modelling. Global Ecology and Biogeography, 27(3), 277–284. https://doi.org/10.1111/geb.12693. Source of present-day and 2100 marine data
1.1.3 Changes in key prey species:
We first identified the key prey species for each species. This can be variable across a species range, but if available evidence suggested at least one major population is highly dependent on a particular prey species, then typically this species would be included. Lists of prey species were compiled from published sources, then verified and expanded following consultation with conservation practitioners. Afterwards we compiled current and projected maps of prey ranges to assess where key prey species may disappear in the near future. If any of the key species are predicted to vanish or drastically reduce in abundance in the current foraging range a given species, we marked this on the summary map. We used several sources to collate range information, but for preference we used data from COPERNICUS as they include projected abundance. For species where this was not available we used habitat suitability instead. In all cases we used RCP 4.5, which is an “intermediate” emissions scenario. For species in the COPERNICUS database we used the 0.6 maximum sustainable yield parameter, which assumes international co-operation to work towards fish-stock sustainability. Our assessment is therefore relatively conservative in terms of changes in prey species.
European Herring Gull key prey species: This species has a very varied diet, including including fish, discards, bivalves, gastropods, crustaceans, squid, insects, refuse and other seabirds, among many other food sources. No key species were identified, so the key prey assessment is not complete
Audouin’s Gull key prey species: sardines (Sardina pilchardus), Atlantic saury (Scomberesox saurus) and blue whiting (Micromesistius poutassou). This species is also known to feed on various other demersal and pelagic fish, as well as various terrestrial food sources, but no other species could be firmly identified as key prey species. Prey species list was compiled from:
- Burger, J., M. Gochfeld, E. F. J. Garcia, and C. J. Sharpe (2020). Audouin’s Gull (Ichthyaetus audouinii), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.audgul1.01
- Calado, J. G., et al. “Seasonal and annual differences in the foraging ecology of two gull species breeding in sympatry and their use of fishery discards.” Journal of Avian Biology 49.1 (2018).
Caspian Gull key prey species: This species has a varied diet of invertebrates. No key species were identified and so the key prey assessment is not complete
Lesser Black-backed Gull key prey species: herring (Clupea harengus), saithe (Pollachius virens) and sandeel species (Ammodytes marinus and Ammodytes tobianus). Many populations also rely heavily on discards, refuse and egg/chick predation. These food sources were not included in this assessment. Prey species list was compiled from:
- Burger, J., M. Gochfeld, G. M. Kirwan, D. A. Christie, and E. de Juana (2020). Lesser Black-backed Gull (Larus fuscus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.lbbgul.01
- Bustnes, Jan Ove, Robert T. Barrett, and Morten Helberg. “Northern Lesser Black-Backed Gulls: What do They Eat?.” Waterbirds 33.4 (2010): 534-540.
- Weiser, E. and H. G. Gilchrist (2020). Glaucous Gull (Larus hyperboreus), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.glagul.01
- Good, T. P. (2020). Great Black-backed Gull (Larus marinus), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.gbbgul.01
- Mallory, M. L., I. J. Stenhouse, H. G. Gilchrist, G. J. Robertson, J. C. Haney, and S. D. Macdonald (2020). Ivory Gull (Pagophila eburnea), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.ivogul.01
- Hatch, S. A., G. J. Robertson, and P. H. Baird (2020). Black-legged Kittiwake (Rissa tridactyla), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bklkit.01
- Arctic Council Publication. “International Black-legged Kittiwake Conservation Strategy and Action Plan.” (2020).
- Fauchald, Per, et al. “The status and trends of seabirds breeding in Norway and Svalbard.” NINA Report (2015): 1151. 84 pp
Sabine’s Gull key prey species: This species has a varied diet of invertebrates and fish. No key species were identified and so the key prey assessment is not complete
Yellow-legged Gull key prey species: Henslow’s swimming crab (Polybius henslowii), sardines (Sardina pilchardus), chub mackeral (Scomber colias), blue whiting (Micromesistius poutassou) and hake (Merluccius merluccius). This species has a varied diet of pelagic and demersal fish, as well as several terrestrial food sources. Note that several of the fish species here may be from fishery discards. Prey species list was compiled from:
- del Hoyo, J., N. Collar, G. M. Kirwan, C. J. Sharpe, and E. F. J. Garcia (2020). Yellow-legged Gull (Larus michahellis), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.yelgul1.01
- COPERNICUS. (2021). Fish abundance and catch data for the Northwest European Shelf and Mediterranean Sea from 2006 to 2098 derived from climate projections. https://doi.org/10.24381/cds.39c97304
- Kesner-Reyes, K., Kaschner, K., Kullander, S., Garilao, C., Barile, J., & Froese., R. (2019). AquaMaps: Predicted range maps for aquatic species. In R. Froese & D. Pauly (Eds.), FishBase. https://www.aquamaps.org
1.1.4 Climate change impacts outside of Europe
European Herring Gull Increased flooding due to sea level rise has led to the reduction or destruction of several populations in the US.- Burger, Joanna, and Michael Gochfeld. Habitat, population dynamics, and metal levels in colonial waterbirds: a food chain approach. CRC Press, 2016.
- Hayward, James L., et al. “Egg cannibalism in a gull colony increases with sea surface temperature.” The Condor 116.1 (2014): 62-73.
- Gilchrist, H. Grant, and Mark L. Mallory. “Declines in abundance and distribution of the ivory gull (Pagophila eburnea) in Arctic Canada.” Biological Conservation 121.2 (2005): 303-309.
- Hamilton, Charmain D., et al. “Spatial overlap among an Arctic predator, prey and scavenger in the marginal ice zone.” Marine Ecology Progress Series 573 (2017): 45-59.
- Yannic, Glenn, et al. “Complete breeding failures in ivory gull following unusual rainy storms in North Greenland.” Polar Research 33.1 (2014): 22749.
- Johansen M, Irgens M, Strøm H, Anker-Nilssen T, Artukhin Y, Barrett R, Barry T, Black J, Danielsen J, Descamps S, Dunn T, Ekker M, Gavrilo M, Gilchrist G, Hansen E, Hedd A, Irons D, Jakobsen J, Kuletz K, Mallory M, Merkel F, Olsen B, Parsons M, Petersen Æ, Provencher J, Robertson G, Rönkä M (2020). International Black-legged Kittiwake Conservation Strategy and Action Plan, Circumpolar Seabird Expert Group. Conservation of Arctic Flora and Fauna, Akureyri, Iceland. ISBN 978-9935-431-85-1. Based on unpublished data.
1.2 Sensitivity (references)
We used a list of candidate traits based on that in Foden & Young (2016) that indicate high sensitivity and identified which, if any, gulls possessed. In brief, we consulted published literature as well as expert knowledge and online databases such as Birdlife (http://datazone.birdlife.org/) and Birds of the World (https://birdsoftheworld.org), to assess whether gulls have either 1) Specialised habitat and/or microhabitat requirement 2) Environmental tolerances or thresholds (at any life stage) that are likely to be exceeded due to climate change 3) Dependence on environmental triggers that are likely to be disrupted by climate change, 4) Dependence on interspecific interactions that are likely to be disrupted by climate change or 5) High rarity.
For more detail and a full list of traits see:- Foden, W. B., & Young, B. E. (2016). IUCN SSC guidelines for assessing species’ vulnerability to climate change. Version 1.0 (Occasional paper of the IUCN Species Survival Commission No. 59)
1.3 Adaptive capacity (references)
We used a list of candidate traits based on that in Foden & Young (2016) that indicate adaptive capacity and identified which, if any, gulls possessed. In brief, we consulted published literature as well as expert knowledge and online databases such as Birdlife (http://datazone.birdlife.org/) and Birds of the World (https://birdsoftheworld.org), to assess whether gulls have either: 1) High phenotypic plasticity. 2) High dispersal ability or 3) High evolvability.
For more detail and a full list of traits see:- Foden, W. B., & Young, B. E. (2016). IUCN SSC guidelines for assessing species’ vulnerability to climate change. Version 1.0 (Occasional paper of the IUCN Species Survival Commission No. 59)