Appendix 1: Sources and references for vulnerability assessment

1.1 Evidence for exposure (references)

1.1.1 Current impacts attributed to climate change:

Razorbill
1 - Extreme storms during the razorbill breeding season have led to wide-spread nest destruction, nesting failure and a net reduction in annual population production

• Newell, Mark, et al. “Effects of an extreme weather event on seabird breeding success at a North Sea colony.” Marine Ecology Progress Series 532 (2015): 257-268 A single extreme summer storm on the Isle of May resulted in wide-spread nest destruction, nesting failure and a net reduction in annual population production. While individual storms cannot be easily be attributed to climate change, severe storms are generally predicted to become worse in the future.

2 - Warmer temperatures correlate with lower adult razorbill mortality, most likely through changes in prey availability.

• Sandvik, Hanno, et al. “The effect of climate on adult survival in five species of North Atlantic seabirds.” Journal of Animal Ecology 74.5 (2005): 817-831 Survival of razorbills goes down as sea surface temperature increase, likely due to changes in fish prey abundance. Mortality most likely occurs in the non-breeding season. Study based on 10 years of breeding data from Hornøya, Norway. Note that this study finds a correlation between temperature and morality, and not a long term trend attributed to climate change.

3 - Warmer temperatures correlate with lower razorbill productivity, most likely through changes in prey availability. In addition, razorbill productivity has slowly declined over time, most likely due to changes in prey availability due to climate change

• Burthe, Sarah, et al. “Phenological trends and trophic mismatch across multiple levels of a North Sea pelagic food web.” Marine Ecology Progress Series 454 (2012): 119-133. Razorbills productivity is correlated with NAO and SST, though lagged. The authors found that long-term changes in razorbill productivity correlate with changes in SST. Most likely through changes in prey availability, but exact mechanism is not known. Study on Skomer Island, Wales.
• Burthe, Sarah, et al. “Phenological trends and trophic mismatch across multiple levels of a North Sea pelagic food web.” Marine Ecology Progress Series 454 (2012): 119-133. Timing of sandeel growth has changed substantially, but laying date has not in razorbills. This likely has resulted in trophic mismatch. However, to date no overall effect on breeding success has been observed. Seabird observations based mostly on Isle of May.

Little Auk
1 - Changes in auks’ prey availability during the breeding season has led to decreased breeding success

• Hovinen, Johanna EH, et al. “Climate warming decreases the survival of the little auk (Alle alle), a high Arctic avian predator.” Ecology and Evolution 4.15 (2014): 3127-3138. At several sites in Svalbard, increased SST is associated with decreased adult survival, probably mediated through prey availability. Suggested mechanism is that an increase in temperature results in a decrease in sea ice and a decrease in ice algal production which in turn results in less food quality and availability. Note that this study finds a correlation between temperature and productivity, and not a long term trend attributed to climate change.
• Kidawa, Dorota, et al. “Parental efforts of an Arctic seabird, the little auk Alle alle, under variable foraging conditions.” Marine Biology Research 11.4 (2015): 349-360. Higher SST during the summer results in longer and less successful foraging trips for nesting auks in Svalbard, and ultimately lowers chick growth and survival. Note that this study finds a correlation between temperature and productivity, and not a long term trend attributed to climate change.
• Hovinen, Johanna EH, et al. “Fledging success of little auks in the high Arctic: do provisioning rates and the quality of foraging grounds matter?.” Polar Biology 37.5 (2014): 665-674. Higher SST in colonies around Svalbard correlates with lower fledging success, though not with provisioning rate by parents. Most likely linked to higher SST resulting in lower prey availability quality.
• Welcker, Jorg, et al. “Flexibility in the bimodal foraging strategy of a high Arctic alcid, the little auk Alle alle.” Journal of Avian Biology 40.4 (2009): 388-399. Essentially corroborates above studies. Auks in Svalbard and Greenland shift their foraging strategy when SST is warmer and forage further away from the colony (very likely due to changes in prey availability). As a result chicks receive less food, though the study does not measure their condition or survival over time.
• Jakubas, Dariusz, Katarzyna Wojczulanis-Jakubas, and Wojciech Walkusz. “Response of dovekie to changes in food availability.” Waterbirds 30.3 (2007): 421-428. This study looks at similar effects to those above, they note warmer waters around Spitsbergen means less easily accessible high-quality food, but that adults are able to compensate somewhat with changes in their foraging strategy. Study based around Spitsbergen, Svalbard.
• Ramírez, Francisco, et al. “Sea ice phenology and primary productivity pulses shape breeding success in Arctic seabirds.” Scientific Reports 7.1 (2017): 1-9. As above, warmer years with less sea ice result in changes in timing of key prey species availability. This in turn correlates with lower breeding performance in Little Auks. Study was based around Spitsbergen, Svalbard.

2 - Change in little auk breeding phenology may lead to trophic mismatch, though no mismatch has been observed so far

• Moe, Børge, et al. “Climate change and phenological responses of two seabird species breeding in the high-Arctic.” Marine Ecology Progress Series 393 (2009): 235-246. Little auks on Svalbard are breeding earlier in correlation to increases in air temperature in the spring. The reason for this is not clear, but may be a result of nesting sites being available earlier due to snow melt. This change in phenology may or may not match prey availability, which may lead to trophic mismatch in the future.

3 - Extreme storms during the non-breeding season have led to mass mortality of little auks (‘wrecks’)

• Clairbaux, Manon, et al. “North Atlantic winter cyclones starve seabirds.” Current Biology 31.17 (2021): 3964-3971. Following heavy storm action, seabird mortality increases due to increased difficulty foraging (rather than increased energetic costs). The authors use a multi-species dataset (puffins, little auks, common murres, and thick-billed murres) over a wide area of the Atlantic basin. They conclude that seabirds around Iceland and the Barents Sea (along with several N. American sites) are particularly vulnerable. Climate change is likely to be a contributing factor to present and future storm mortality.

Black Guillemot
1 - Storms and increased water level have led to flooding and destruction of guillemot nests, and therefore lower breeding success. The frequency of such flooding events is likely to increase.

• Hof, Anouschka R., Joep AHM Crombag, and Andrew M. Allen. “The ecology of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region: insights into their diet, survival, nest predation and moment of fledging.” Bird Study 65.3 (2018): 357-364. Storms and increased water level leads to flooding of nests and lower breeding success in the Baltic. The authors note that such flooding events are likely to further increase.

2 - Range expansion of American mink, partly assisted by climate change, has led to increased rates of predation at guillemot colonies.

• Buchadas, Ana RC, and Anouschka R. Hof. “Future breeding and foraging sites of a southern edge population of the locally endangered Black Guillemot Cepphus grylle.” Bird Study 64.3 (2017): 306-316. Black guillemots are particularly vulnerable to predation by American mink, which is currently increasing in range and abundance in Europe. This range expansion has likely been assisted by climate change and therefore predation is likely to worsen across the species range. The study focusses on the Baltic but suggests anywhere the mink is expanding is likely to have similar issues in the future

3 - Guillemot have shifted their laying date, most likely linked to an increase in sea surface temperature and prey availability

• Greenwood, Julian G. “Earlier laying by Black Guillemots Cepphus grylle in Northern Ireland in response to increasing sea-surface temperature.” Bird Study 54.3 (2007): 378-379. A small population in N. Ireland has shifted its laying date in correlation with SST.

Atlantic Puffin
1 - Changes in puffins’ prey availability during breeding season has led to decreased breeding success

• Durant, Joël M., et al. “Regime shifts in the breeding of an Atlantic puffin population.” Ecology Letters 7.5 (2004): 388-394. In the Norwegian sea, changes in the NAO have affected food availability and therefore puffin success and breeding timing. Study used a multi-decadal dataset from Hernyken, Northern Norway.
• Møller, Anders Pape, Wolfgang Fiedler, and Peter Berthold, eds. Effects of climate change on birds. OUP Oxford (2010) Higher water temperature in the Norwegian sea has resulted in a shift in herring stock to the north, and a spatial mismatch between puffins and prey.
• Barrett, Robert T., Erlend B. Nilsen, and Tycho Anker-Nilssen. “Long-term decline in egg size of Atlantic puffins Fratercula arctica is related to changes in forage fish stocks and climate conditions.” Marine Ecology Progress Series 457 (2012): 1-10. Puffin eggs in several Norwegian populations are smaller in years when capelin and herring is less available, which is linked to climate change. This likely is also an indicator of population health and may be driving declines.
• Frederiksen, Morten, et al. “Climate, copepods and seabirds in the boreal Northeast Atlantic–current state and future outlook.” Global change biology 19.2 (2013): 364-372. Declines in puffins (and other species) across the North Sea correlates to marine suitability for copepods (a key prey for many fish and seabirds), which has decreased in recent years (though the authors found a weaker link in Norway).
• 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. Puffin productivity and survival decreases in puffins around the Forth and Tay region as temperature gets higher. Most likely linked to prey availability.
• Fauchald, Per, et al. “The status and trends of seabirds breeding in Norway and Svalbard.” (2015). Severe declines of puffins have occurred in most areas of Norway, cause is not known but changes in food abundance and timing are concluded to be the most probable cause.
• Hansen, Erpur S., et al. “Centennial relationships between ocean temperature and Atlantic puffin production reveal shifting decennial trends.” Global Change Biology (2021). Sea surface temperature is a strong predictor of puffin breeding success in a breeding population in Iceland, most likely through sandeel abundance during the winters. Milder winters result in fewer sandeels in the following summer. Study uses a long term dataset (130 years) based on breeding success in Vestmannaeyjar, Iceland.
• Fayet, Annette L., et al. “Local prey shortages drive foraging costs and breeding success in a declining seabird, the Atlantic puffin.” Journal of Animal Ecology 90.5 (2021): 1152-1164. Puffin tracking data has shown that when they are forced to forage further (using data from Iceland, Norway and Wales) breeding success decreases. Changes in food availability are closely related to temperature and are likely to get worse.

2 - Changes in puffins’ prey availability during non-breeding season has led to increased mortality

• Harris, Michael P., et al. “Wintering areas of adult Atlantic puffins Fratercula arctica from a North Sea colony as revealed by geolocation technology.” Marine Biology 157.4 (2010): 827-836. Isle of May puffins are suffering over-winter mortality and are shifting their wintering distribution from the North Sea to the Atlantic, most likely due to changes in North Sea.
• “Scottish wildlife trust report on Atlantic puffin” (2018). Colony declines on the east coast of Scotland are attributed to lack of prey during the breeding and non-breeding season. The report notes the availability of suitable prey during the non-breeding season is critical for long-term health of puffin populations.

3 - Changes in vegetation has led to fewer suitable puffin nest-sites

• Van Der Wal, René., et al. “Multiple anthropogenic changes cause biodiversity loss through plant invasion.” Global Change Biology 14.6 (2008): 1428-1436. Expansion of tree mallow Lavatera arboreahas, in part due to climate change, substantially reduced suitable nesting habitat for Atlantic puffins at several colonies in the Forth and Tay region.
• 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. Update on the above confirming the impacts of tree mallow on puffins and the scale of the problem in Scotland.

4 - Extreme storms during the non-breeding season have led to mass-mortality of puffins (‘wrecks’)

• Mitchell, I., et al. “Impacts of climate change on seabirds, relevant to the coastal and marine environment around the UK.” MCCIP Science Review (2020): 382-399. Winter storms can cause mass mortality (and have recently in 2013/14 storms), wrecks have been observed off the coast of France and the east coast of England. While individual storms cannot easily be attributed to climate change, most predictions are confident extreme Atlantic storms will become more frequent.
• Clairbaux, Manon, et al. “North Atlantic winter cyclones starve seabirds.” Current Biology 31.17 (2021): 3964-3971. Following heavy storm action, seabird mortality increases due to increased difficulty foraging (rather than increased energetic costs). The authors use a multi-species dataset (puffins, little auks, common murres, and thick-billed murres) over a wide area of the Atlantic basin. They conclude that seabirds around Iceland and the Barents Sea (along with several N. American sites) are particularly vulnerable. Climate change is likely to be a contributing factor to present and future storm mortality.

Common Murre
1 - High-wind events in the non-breeding season have led to mass mortality of murres in recent years.

• Louzao, Maite, et al. “Threshold responses in bird mortality driven by extreme wind events.” Ecological Indicators 99 (2019): 183-192. High wind events in the winter have caused several mass mortality events (“wrecks”) in NE Atlantic, though this study focusses on bodies washed up in Bay of Biscay. Study suggests high wind events are likely to become more common and result in more deaths in the future.

2 - Extreme storms during the non-breeding season have led to mass mortality of murres (‘wrecks’).

• Clairbaux, Manon, et al. “North Atlantic winter cyclones starve seabirds.” Current Biology 31.17 (2021): 3964-3971. Following heavy storm action, seabird mortality increases due to increased difficulty foraging (rather than increased energetic costs). The authors use a multi-species dataset (puffins, little auks, common murres, and thick-billed murres) over a wide area of the Atlantic basin. They conclude that seabirds around Iceland and the Barents Sea (along with several N. American sites) are particularly vulnerable. Climate change is likely to be a contributing factor to present and future storm mortality.

3 - More frequent extreme storms during murres’ breeding season has increased foraging difficulty and reduced food fed to chicks.

• Finney, Suzanne K., Sarah Wanless, and Michael P. Harris. “The effect of weather conditions on the feeding behaviour of a diving bird, the Common Guillemot Uria aalge.” Journal of Avian Biology (1999): 23-30. Stormy weather affects the quantity and size of food that adults can provide to chicks, and increases in summer storm frequency may result in lowered foraging efficiency. Study was conducted on Isle of May. Extreme storms in the Atlantic are likely to become more frequent in the future and further disrupt the breeding season.

4 - Changes in murres’ prey availability during the breeding season has led to decreased breeding success

• Wanless, Sarah, et al. “Low energy values of fish as a probable cause of a major seabird breeding failure in the North Sea.” Marine Ecology Progress Series 294 (2005): 1-8. Murres (aka guillemots) on the Isle of May were forced to switch to less nutritious prey due to a lack of sandeels. This resulted in substantially lower chick condition and fledging success. Sandeel decrease is likely at least partially due to climate change
• Irons, David B., et al. “Fluctuations in circumpolar seabird populations linked to climate oscillations.” Global Change Biology 14.7 (2008): 1455-1463. The authors find, using a multi-decade dataset, that murre population size across the Arctic is strongly correlated to sea surface temperature. Rapid temperature shifts (either hotter or cooler) resulted in a decrease in population size. Note: this study does not explicitly investigate anthropogenic climate change, but does show a clear linkage between rapid climate change and population declines.
• Frederiksen, Morten, et al. “Climate, copepods and seabirds in the boreal Northeast Atlantic–current state and future outlook.” Global change biology 19.2 (2013): 364-372. Breeding success on the Isle of May was strongly correlated to suitable climate for local copepods, and increases in temperature have lowered suitability for copepods and therefore breeding success in recent years. Projections also show that this drop in suitability will continue and worsen in the future. Interestingly, the authors did not find evidence of such a link in Rost, Norway.
• Sandvik, Hanno, et al. “The effect of climate on adult survival in five species of North Atlantic seabirds.” Journal of Animal Ecology 74.5 (2005): 817-831 The authors found that both common murres (guillemots) and thick-billed murres (Brünnich’s guillemots) were negatively affected by warmer temperatures causing alterations to their food webs, they note that these trends are likely to continue. The data spanned 14 years of observation at a colony on Hornøya, off Northern Norway in the western Barents Sea

5 - Murres are more likely to skip breeding in warmer weather, and this behaviour is becoming more frequent. While this is a cause for concern, it is unclear what effect this will have on the population in the long-term.

• Reed, Thomas E., Mike P. Harris, and Sarah Wanless. “Skipped breeding in common guillemots in a changing climate: restraint or constraint?.” Frontiers in Ecology and Evolution 3 (2015): 1. Murres (aka guillemots) are more frequently skipping breeding in warm years, this may increase in the future. However it’s uncertain whether this will have long term consequences on the population. Study conducted on Isle of May, Scotland

6 - Heatwaves can result in significant murre chick mortality. The frequency and severity of heatwaves is likely to increase.

• __Elmar Ballstaedt (personal correspondance); See also https://www.jordsand.eu/2018/08/14/bruterfolg-deutscher-seev%C3%B6gel-durch-wetterkapriolen-schlecht-wie-lange-nicht-mehr__ The heatwave of summer 2018 resulted in fewer breeding attempts and increased chick mortality in many species on Helgoland, most likely due to heat stress. Many seabirds on Helgoland are declining which could in part be due to climate change.

7 - Common murres have changed their phenology, most likely in response to climate change. Changes in temperature and prey availability correlate to change in laying date.

• Wanless, Sarah, et al. “Long-term changes in breeding phenology at two seabird colonies in the western North Sea.” Ibis 151.2 (2009): 274-285. Common murres in the North Sea have changed their laying date, most likely due to changes in temperature and prey availability. Study on Isle of May, Scotland.

Thick-billed Murre
1 - Reduced prey availability during non-breeding season

• Descamps, Sébastien, Hallvard Strøm, and Harald Steen. “Decline of an arctic top predator: synchrony in colony size fluctuations, risk of extinction and the subpolar gyre.” Oecologia 173.4 (2013): 1271-1282. Many colonies in Svalbard are declining, and if trends continue there is a risk of local extinction. Declines strongly correlate with marine change, though the exact mechanism is unknown. Authors suggest that deterioration of the feeding conditions in the winter affected bird survival, particularly juvenile survival, and that local variations in spring and summer conditions affected breeding propensity and breeding success of murres.
• Sandvik, Hanno, et al. “The effect of climate on adult survival in five species of North Atlantic seabirds.” Journal of Animal Ecology 74.5 (2005): 817-831. Authors found that both the common murres (guillemots) and thick-billed murres (Brünnich’s guillemots) were negatively affected by warmer temperatures causing alterations to their food webs, they note that these trends are likely to continue. The data spanned 14 years of observation at a colony on Hornøya, off Northern Norway in the western Barents Sea

2 - Reduced prey availability during breeding season

• Garðarsson, Arnþór, Guðmundur A. Guðmundsson, and Kristján Lilliendahl. “Svartfugl í íslenskum fuglabjörgum 2006–2008.” Bliki 33 (2019): 35-46. Reviews the population trends in various seabird species in Iceland. Particularly highlights the drastic decline of thick-billed murres (Brünnich’s guillemots) across Iceland. Sharp declines correspond to crash in key prey species and changes in marine ecosystems linked to rapid temperature change.
• Descamps, Sébastien, Hallvard Strøm, and Harald Steen. “Decline of an arctic top predator: synchrony in colony size fluctuations, risk of extinction and the subpolar gyre.” Oecologia 173.4 (2013): 1271-1282. Local variations in Svalbard spring and summer conditions affected breeding propensity and breeding success of murres. See 1) for more details.
• Fluhr, Julie, et al. “Weakening of the subpolar gyre as a key driver of North Atlantic seabird demography: a case study with Brünnich’s guillemots in Svalbard.” Marine Ecology Progress Series 563 (2017): 1-11 An update and expansion on the previous paper, focussing on murres on Bear Island, Svalbard. Confirms strong correlation of adult annual survival and the strength of Atlantic subpolar gyre.

3 - Correlation between species and climate. Mechanism unknown.

• Bonnet-Lebrun, Anne-Sophie, et al. “Cold comfort: Arctic seabirds find refugia from climate change and potential competition in marginal ice zones and fjords.” Ambio 51.2 (2022): 345-354. Thick-billed murres (Brünnich’s guillemots) populations in Iceland have declined in correlation with rising sea surface temperatures. In addition, populations associated with higher sea temperatures have declined faster and tend to be smaller than those near refugia of cold water. The authors investigate the role of competition (with little significant effect), but link to various Icelandic studies which provide evidence for prey availability being the main reason behind the declines
• Irons, David B., et al. “Fluctuations in circumpolar seabird populations linked to climate oscillations.” Global Change Biology 14.7 (2008): 1455-1463. The authors find, using a multi-decade dataset, that murre population size across its range in the Arctic is strongly correlated to sea surface temperature. Rapid temperature shifts (either hotter or cooler) resulted in a decrease in population size, probably mediated through changes in underlying food-webs. Note: this study does not explicitly investigate anthropogenic climate change, but does show a clear linkage between rapid climate change and population declines.

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 Razorbill, Little Auk, Black Guillemot, Atlantic Puffin, Common Murre, and Thick-billed Murre 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 Razorbill, Little Auk, Black Guillemot, Atlantic Puffin, Common Murre, and Thick-billed Murre we included the following marine variables: ea surface temperature (during the winter), salinity, maximum chlorophyll concentration, bathymetry (depth and variance)

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.

Razorbill key prey species: sandeel species (Ammodytes marinus and Ammodytes tobianus), herring (Clupea harengus), capelin (Mallotus villosus) and sprat (Sprattus sprattus). Prey species list was compiled from:

• Fauchald, Per, et al. “The status and trends of seabirds breeding in Norway and Svalbard.” NINA Report (2015): 1151. 84 pp. 
• Barrett, Robert T. “The diet, growth and survival of Razorbill Alca torda chicks in the southern Barents Sea.” Ornis Norvegica 38 (2015): 25-31.

Little Auk key prey species: Calanus glacialis, Calanus hyperboreus and Apherusa glacialis. Note that since data regarding climate change and copepod range shifts are not readily available, a full prey loss assessment could not be carried out for this species. Prey species list was compiled from:

• Harding, Ann Marie Aglionby, et al. “Estimating prey capture rates of a planktivorous seabird, the little auk (Alle alle), using diet, diving behaviour, and energy consumption.” Polar Biology 32.5 (2009): 785-796.
• Amélineau, Françoise, et al. “Arctic climate change and pollution impact little auk foraging and fitness across a decade.” Scientific reports 9.1 (2019): 1-15.

Black Guillemot key prey species: sandeel species (Ammodytes marinus), butterfish (Pholis gunnellus), eelpout (Zoarces viviparus) and sea scorpion (Taurulus bubalis). Prey species list was compiled from:

• Fauchald, Per, et al. “The status and trends of seabirds breeding in Norway and Svalbard.” NINA Report (2015): 1151. 84 pp. 
• Ewins, P. J. “The diet of black guillemots Cepphus grylle in Shetland.” Ecography 13.2 (1990): 90-97.
• Hario, Martti. “Chick growth and nest departure in Baltic Black Guillemots Cepphus grylle.” Ornis Fennica 78.3 (2001): 97-108.
• BirdLife International (2021) Species factsheet: Cepphus grylle. Downloaded from http://www.birdlife.org on 01/06/2021
• Hof, Anouschka R., Joep AHM Crombag, and Andrew M. Allen. “The ecology of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region: insights into their diet, survival, nest predation and moment of fledging.” Bird Study 65.3 (2018): 357-364.
• Barrett, Robert T., and Tycho Anker-Nilssen. “Egg-laying, chick growth and food of Black Guillemots.”

Atlantic Puffin key prey species: sandeel species (Ammodytes marinus and Ammodytes tobianus), herring (Clupea harengus), capelin (Mallotus villosus) and sprat (Sprattus sprattus). Prey species list was compiled from:

• Fayet, A. L., Clucas, G. V., Anker-Nilssen, T., Syposz, M., & Hansen, E. S. (2021). Local prey shortages drive foraging costs and breeding success in a declining seabird, the Atlantic puffin. Journal of Animal Ecology, 90(5), 1152–1164. https://doi.org/10.1111/1365-2656.13442
• BirdLife International (2021) Species factsheet: Fratercula arctica. Downloaded from http://www.birdlife.org on 01/06/2021

Common Murre key prey species: sprat (Sprattus sprattus), sandeels species (Ammodytes marinus and Ammodytes tobianus), capelin (Mallotus villosus), herring (Clupea harengus), Atlantic cod (Gadus morhua), saithe (Pollachius virens) and haddock (Melanogrammus aeglefinus). Prey species list was compiled from:

• Kadin, Martina, et al. “Contrasting effects of food quality and quantity on a marine top predator.” Marine Ecology Progress Series 444 (2012): 239-249.
• BirdLife International (2021) Species factsheet: Uria aalge. Downloaded from http://www.birdlife.org on 01/06/2021
• Ainley, D. G., D. N. Nettleship, and A. E. Storey (2021). Common Murre (Uria aalge), version 2.0. In Birds of the World (S. M. Billerman, P. G. Rodewald, and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.commur.02
• Fauchald, Per, et al. “The status and trends of seabirds breeding in Norway and Svalbard.” (2015).

Thick-billed Murre key prey species: sandeel species (Ammodytes marinus and Ammodytes tobianus), herring (Clupea harengus), capelin (Mallotus villosus), Atlantic cod (Gadus morhua) and polar cod (Boreogadus saida). Prey species list was compiled from:

• Barrett, Robert T. “Atlantic puffin Fratercula arctica and common guillemot Uria aalge chick diet and growth as indicators of fish stocks in the Barents Sea.” Marine Ecology Progress Series 230 (2002): 275-287.
• Fauchald, Per, et al. “The status and trends of seabirds breeding in Norway and Svalbard.” NINA Report (2015): 1151. 84 pp. 

Prey range information for all species were compiled from:

• 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

Little Auk
Loss of sea ice and new prey items due to climate change has led to increased little auk breeding success in Greenland

• Amélineau, Françoise, et al. “Arctic climate change and pollution impact little auk foraging and fitness across a decade.” Scientific reports 9.1 (2019): 1-15.

Atlantic Puffin
Some colonies in North America have changed their laying phenology, presumably in response to temperature and/or prey availability. Some recent observations have reported this has also occurred in Europe.

• Major, Heather L., et al. “Contrasting phenological and demographic responses of Atlantic Puffin (Fratercula arctica) and Razorbill (Alca torda) to climate change in the Gulf of Maine.” Elem Sci Anth 9.1 (2021): 00033.
• Erpur Hansen (Personal Correspondance)

Thick-billed Murre
Thick-billed murres are known to be impacted by climate change outside of Europe. Impacts include increased predation by polar bears, increased parasitism by mosquitoes (leading to breeding failure), and increased mortality caused by algal blooms.

• Gaston, Anthony J., and Kyle H. Elliott. “Effects of climate-induced changes in parasitism, predation and predator-predator interactions on reproduction and survival of an Arctic marine bird.” Arctic (2013): 43-51.
• Kuletz, Kathy et al. “Chapter 3.5: Seabirds” in “State of the Arctic Marine Biodiversity Report”. Conservation of Arctic Flora and Fauna International Secretariat (2017): 129-147

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, auks 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 auks 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, auks 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 auks 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)