Oceanography The Official Magazine of
The Oceanography Society
Volume 35 Issue 3-4

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Volume 35, No. 3-4
Pages 156 - 157


SIDEBAR • Alaskan Seabird Die-Offs

By Robb Kaler  and Kathy Kuletz  
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Prior to 2015, seabird die-offs in Alaskan waters (Northern Gulf of Alaska, eastern Bering Sea, eastern Chukchi Sea) were rare, typically occurred in mid-winter, and were linked to epizootic disease events (Bodenstein et al., 2015) or above-average ocean temperatures associated with strong El Niño-Southern Oscillation events. An example was late summer of 1997, a year with unusually warm waters in the southeastern Bering Sea, when possibly as many as 10% of the several million short-tailed shearwaters (Ardenna tenuitortris) present in the area died of starvation because their principal prey, euphausiids, were scarce or hard to find in a widespread coccolithophore bloom (Baduini et al., 2001). Since 2015, similar or smaller mass mortality events have been annual occurrences. In 2015, between 470,000 and 1.03 million common murres (Uria aalge) were estimated to have died in the Gulf of Alaska due to anomalous ocean conditions and the impacts on forage fish associated with the 2014–2016 Pacific marine heatwave (Piatt et al., 2020; Arimitsu et al., 2021). Another large die-off event occurred during late summer of 2019 (Figure 1), when over 10,000 carcasses of short-tailed shearwaters washed onto beaches of Bristol Bay and the Alaska Peninsula in the southeastern Bering Sea. Total mortality during that summer was likely much greater than reported given the region’s expansive coastline and sparse human population.


FIGURE 1. Location and number of seabird carcasses reported in Alaska during 2019. Data compilation and map were provided by the Coastal Observation and Seabird Survey Team (COASST; University of Washington, Seattle), and relied on data collected by community members, Alaska Sea Grant, the US National Park Service, and the US Fish and Wildlife Service. > High res figure


Seabirds are natural indicators of the status of marine ecosystems, and since at least 2017, die-offs in the northern Bering and southern Chukchi Seas (including some reports from the Russia Far East) have been concurrent with massive ecological shifts resulting from increased ocean temperatures coupled with decreased duration and extent of sea ice in those seas. Changes include a decrease in the large crustacean zooplankton that support planktivorous seabirds (Duffy-Anderson et al., 2019). In addition, there has been significant reduction of the cold pool thermal barrier, a layer of <2°C water near the seafloor that restricts species like Pacific cod (Gadus macrocephalus) and walleye pollock (Gadus chalcogrammus) from entering the northern Bering Sea. More recent studies in the Pacific Arctic region indicate the northward movement of adult cod and pollock (Duffy-Anderson et al., 2019; Eisner et al., 2020) that might compete with seabirds for food.

Seabird species affected since 2017 in eastern Bering and Chukchi Seas include planktivorous birds such as auklets (Aethia spp.) and shearwaters, piscivorous murres, puffins (Fratercula spp.), and kittiwakes (Rissa spp.), as well as some benthic-feeding sea ducks (Somateria spp.). Involvement of a range of seabird species that consume different prey, and localized mortality events throughout summer across a vast region (albeit with relatively low numbers at individual sites), signal broadscale, ecosystem-level impacts at multiple trophic levels. Such wildlife mortality events are of concern not only for coastal communities that rely on ocean resources for their nutritional, cultural, and economic well-being but also signal concern for the state of subarctic and Arctic oceans.

While starvation has been identified as the main cause of death for carcasses examined by US Geological Survey (USGS) National Wildlife Health Center scientists, university and federal researchers continue to evaluate other possible contributing factors. To date, highly pathogenic diseases have not been detected in tested carcasses. Exposure to saxitoxin, associated with harmful algal blooms, was detected in seabird tissues in 2017; however, direct neurotoxic results from saxitoxin could not be confirmed, and starvation appeared to be the proximate cause of death among birds examined (Van Hemert et al., 2021). USGS researchers at the Alaska Science Center continue to investigate algal toxins in marine invertebrates and forage fish and are conducting experimental trials to determine effects of saxitoxin on seabird behavior and health, which may include emaciation.

With seabird mortalities reported over a wide geographic region and throughout summer and fall on an annual basis, how are birds doing at breeding colonies? Observations at northern seabird breeding colonies indicate lack of breeding attempts or very late and unsuccessful breeding between 2017 and 2019 (Romano et al., 2020; Will et al., 2020). Although these observations suggest that the seabird die-offs stem from multiple ecosystem changes associated with abnormally high ocean temperatures, including forage fish quantity and quality, unfavorable foraging conditions (competition with fish), or exposure to harmful algal bloom biotoxins, there still is no confirmed “smoking gun.”

The bottom-up effects linked with changes in the prey base and top-down effects associated with increased metabolic rate, along with food demands of competing fish species that could reduce prey availability to seabirds and marine mammals, is referred to as an “ectothermic vise” by Piatt et al. (2020). With increasing ocean temperatures and decreasing sea ice, the next decade will be critical for upper trophic organisms and human communities adapting to a fast-changing environment in northern Alaska.



Monitoring seabird die-offs has been a collaboration of local community members from Nome, Savoonga, Gambell, Shishmaref, St. Paul Island, Unalaska, and federal and state agencies. We thank the following for assisting with collection of data, examining and testing carcasses, and summary reports: Brandon Ahmasuk and Austin Ahmasuk (Kawerak Inc.); Gay Sheffield (University of Alaska Fairbanks/Alaska Sea Grant); Julia Parrish, Timothy Jones, and Jaqueline Lindsey (Coastal Observation and Seabird Survey Team); Stacia Backensto (US National Park Service); Barbara Bodenstein and Robert Dusek (USGS National Wildlife Heather Center); and Caroline Van Hemert, Mathew Smith, and Sarah Schoen (USGS Alaska Science Center). Oceanographic and prey links in areas with seabird die-offs are being investigated by the National Oceanic and Atmospheric Administration, University of Alaska Fairbanks, University of Massachusetts, and Woods Hole Oceanographic Institution, with support from the North Pacific Research Board and National Science Foundation. Reviews by George L. Hunt and an anonymous reviewer greatly improved the text.

Kaler, R., and K. Kuletz. 2022. Alaskan seabird die-offs. Oceanography 35(3–4):156–157, https://doi.org/10.5670/oceanog.2022.118.


Arimitsu, M.L., J.F. Piatt, S. Hatch, R.M. Suryan, S. Battan, M.A. Bishop, R.W. Campbell, H. Coletti, D. Cushing, K. Gorman, and others. 2021. Heatwave-induced synchrony within forage fish portfolio disrupts energy flow to top pelagic predators. Global Change Biology 27(9):1,859–1,878, https://doi.org/10.1111/gcb.15556.

Baduini, C.L., K.D. Hyrenbach, K.O. Coyle, A. Pinchuk, V. Mendenhall, and G.L. Hunt Jr. 2001. Mass mortality of short-tailed shearwaters in the eastern Bering Sea during summer 1997. Fisheries Oceanography 10:117–130, https://doi.org/10.1046/j.1365-2419.2001.00156.x.

Bodenstein, B., K. Beckman, G. Sheffield, K. Kuletz, C. Van Hemert, B. Berlowski, and V. Shearn-Bochsler. 2015. Avian cholera causes marine bird mortality in the Bering Sea of Alaska. Journal of Wildlife Disease 51(4):934–937, https://doi.org/10.7589/2014-12-273.

Duffy-Anderson, J.T., P. Stabeno, A.G. Andrews III, K. Cieciel, A. Deary, E. Farley, C. Fugate, C. Harpold, R. Heintz, D. Kimmel, and others. 2019. Responses of the northern Bering Sea and southeastern Bering Sea pelagic ecosystems following record-breaking low winter sea ice. Geophysical Research Letters 46:9,833–9,842, https://doi.org/​10.1029/2019GL083396.

Eisner, L.B., Y.I. Zuenko, E.O. Basuk, L.L. Britt, J.T. Duffy-Anderson, S. Kotwicki, C. Ladd, and W. Cheng. 2020. Environmental impacts on walleye pollock (Gadus chalcogrammus) distribution across the Bering Sea shelf. Deep Sea Research Part II 181–182:104881, https://doi.org/10.1016/​j.dsr2.2020.104881.

Piatt, J.F., J.K. Parrish, H.M Renner, S.K. Schoen, T.T. Jones, M.L. Arimitsu, K.J. Kuletz, B. Bodenstein, M. Garcia-Reyes, R.S. Duerr, and others. 2020. Extreme mortality and reproductive failure of common murres resulting from the northeast Pacific marine heatwave of 2014–2016. PLoS ONE 15(1):e0226087, https://doi.org/10.1371/journal.pone.0226087.

Romano, M., H.M. Renner, K.J. Kuletz, J.K. Parrish, T.T. Jones, H.K. Burgess, D.A. Cushing, and D. Causey. 2020. Die-offs and reproductive failure of murres in the Bering and Chukchi Seas in 2018. Deep Sea Research Part II 181–182:104877, https://doi.org/10.1016/j.dsr2.2020.104877.

Van Hemert, C., R.J. Dusek, M.M. Smith, R. Kaler, G. Sheffield, L.M. Divine, K.J. Kuletz, S. Knowles, J.S. Lankton, D.R. Hardison, and others. 2021. Investigation of algal toxins in a multispecies seabird die-off in the Bering and Chukchi seas. Journal of Wildlife Diseases 57(2):399–407, https://doi.org/​10.7589/​JWD-D-20-00057.

Will, A., A. Takahashi, J.-B. Thiebot, A. Martinez, E. Kitaiskaia, L. Britt, D. Nichol, J. Murphy, A. Dimond, S. Tsukamoto, and others. 2020. The breeding seabird community reveals that recent sea ice loss in the Pacific Arctic does not benefit piscivores and is detrimental to planktivores. Deep Sea Research Part II 181–182:104902, https://doi.org/10.1016/​j.dsr2.2020.104902.

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