Bering Sea | Seabirds
What dead birds tell us about a warming world Presenter: Julia Parrish , jparrish@uw.edu, University of Washington Timothy Jones , timothy.t.jones@gmail.com, University of Washington Jackie Lindsey , jackieklindsey@gmail.com, University of Washington
As long-lived, low fecundity, abundant and highly visible upper-level trophics, seabirds are frequently cited as marine ecosystem indicator species. Whereas short-term system perturbations may be absorbed by behavioral responses, or changes in reproductive output, larger-scale perturbations should provoke increased mortality, at least as a first wave of response. Since 2014 the North Pacific has experienced multiple seabird mass mortality events (MMEs), including at least five major events from 2014 through 2021 collectively encompassing several million birds. During this same period of time several types of warming have occurred, including the northeast Pacific marine heatwave, an El Niño event, and the intensification of arctic/sub-arctic warming in the Bering and southern Chukchi Sea. Despite the obvious overlap in system warming and seabird MMEs, the operational relationship between elevated sea temperatures and the observed effects on seabirds is poorly understood. We compiled beached bird data spanning 30 years of monitoring from four citizen science programs stretching from central California north to the Bering Strait region, as well as from community reports sent to the U.S. Fish and Wildlife Service, to examine whether and to what extent: (1) marine heatwaves provoke seabird mortality events: (2) the duration of marine heatwave increases the likelihood of mortality event occurrence; and (3) the functional relationship between ocean warming and mortality event characteristics. Mass mortality events, particularly large-scale, long duration events, were positively associated with marine heatwaves, with stronger associations following prolonged marine heatwaves (>90 days in duration). Predictable seasonal patterns in beached bird abundance were severely disrupted following major marine heatwave or El Niño events, indicative of short-term (i.e. distributional, elevated mortality) and multi-annual (i.e. reductions in local abundance and/or compensatory mortality) effects on marine bird populations. Event characteristics, including magnitude, duration and spatial extent were all positively associated with increased temperatures, collectively indicative of events becoming larger and longer-lasting, with higher carcass counts under warmer conditions. Collectively, these data indicate that sudden, prolonged warming will result in a demonstrative uptick in seabird mortality, as the system resets to a lower carrying capacity for these upper-trophic predator
Alaska Marine Science Symposium 2023 53
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