Marine bird mass mortality events as an indicator of the impacts of ocean warming

Timothy Jones; Julia K. Parrish; Jacqueline Lindsey; Charlie Wright; Hillary K. Burgess; Jane Dolliver; Lauren Divine; Robert Kaler; David Bradley; Graham Sorenson; Rémi Torrenta; Stacia Backensto; Heather A. Coletti; James T. Harvey; Hannahrose M. Nevins; Erica Donnelly-Greenan; David L. Sherer; Jan Roletto; Kirsten Lindquist

doi:10.3354/meps14330

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Marine Ecology Progress Series

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MEPS 737:161-181 (2024) - DOI: https://doi.org/10.3354/meps14330

Theme Section: How do marine heatwaves impact seabirds?

Marine bird mass mortality events as an indicator of the impacts of ocean warming

Timothy Jones^1,*, Julia K. Parrish¹, Jacqueline Lindsey¹, Charlie Wright¹, Hillary K. Burgess¹, Jane Dolliver¹, Lauren Divine², Robert Kaler³, David Bradley⁴, Graham Sorenson⁴, Rémi Torrenta⁴, Stacia Backensto⁵, Heather A. Coletti⁵, James T. Harvey⁶, Hannahrose M. Nevins⁶, Erica Donnelly-Greenan⁶, David L. Sherer⁷, Jan Roletto⁸, Kirsten Lindquist^8,9

¹School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98105, USA
²Ecosystem Conservation Office, Aleut Community of St. Paul, Anchorage, Alaska 99503, USA
³Migratory Bird Management, US Fish and Wildlife Service, Anchorage, Alaska 99503, USA
⁴Birds Canada/Oiseaux Canada, Delta, British Columbia V4G 2T9, Canada
⁵Inventory and Monitoring Program, National Park Service, Fairbanks, Alaska 99709, USA
⁶BeachCOMBERS, Moss Landing Marine Laboratories, Moss Landing, California 95039, USA
⁷BeachCOMBERS, US Fish and Wildlife Service, Ventura, California 93003, USA
⁸Greater Farallones National Marine Sanctuary, NOAA, NOS, ONMS, San Francisco, California 94129, USA
⁹Greater Farallones Association, affiliate NOAA, NOS, ONMS, Greater Farallones National Marine Sanctuary, San Francisco, California 94129, USA

*Corresponding author: timothy.t.jones@gmail.com

ABSTRACT: The frequency and severity of marine heatwaves (MHWs), an emergent property of global warming, has led to large-scale disruptions to marine ecosystems. As upper trophic species, marine birds reflect shifts in trophic structure and stability; therefore, a sharp increase in marine bird mortality is a clear signal of ecosystem impact. In this study, we analyzed 29 yr (1993-2021) of beached bird monitoring data (~90000 surveys) to identify marine bird mortality events throughout the Northeast Pacific and Alaska, USA, and examined linkages to ocean-climate variability. Mortality events were documented throughout the study period, but massive events (>500 km in extent, >10 carcasses km^-1) occurred infrequently (n = 5), with an unprecedented sequence from 2014-2019. Event characteristics, including encounter rate (carcasses km^-1), duration, and spatial extent, were positively related to prior-year averaged sea surface temperature anomaly, with event magnitude (product of encounter rate, extent, and duration) displaying a step-like transition, increasing 5-fold between +0°C and +1°C above baseline (1981-2010) temperatures. Mortality events occurred more frequently following MHWs, and a common sequence of mortality events (at 1-6 and 10-16 mo after heatwave onset) was observed in the California Current large marine ecosystem following 3 prolonged MHW events. Following the second wave of mortality at 10-16 mo after MHW onset, a consistent 16 mo period of depressed carcass encounter rates ensued. Given continued global warming, our results point to more frequent large-scale mortality events and the potential for a new lower carrying capacity for marine birds in the Northeast Pacific.

KEY WORDS: Extreme events · Marine heatwaves · Citizen science · Seabird wrecks · North Pacific

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Cite this article as: Jones T, Parrish JK, Lindsey J, Wright C and others (2024) Marine bird mass mortality events as an indicator of the impacts of ocean warming. Mar Ecol Prog Ser 737:161-181. https://doi.org/10.3354/meps14330

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