Lingering impacts of the 2014-2016 northeast Pacific marine heatwave on seabird demography in Cook Inlet, Alaska (USA)

A protracted period (2014-2016) of anomalously warm water in the northeast Pacific Ocean precipitated an extensive die-off common murres Uria aalge (hereafter ‘murres’) during 2015-2016, accompanied by reduced colony attendance and reproductive success black-legged kittiwakes Rissa tridactyla (‘kittiwakes’) starting 2015. Most died starvation following a large-scale reduction abundance quality forage fish. To assess murre kittiwake recovery marine heatwave, we monitored their demographics at 2 colonies (Chisik Gull Islands) Cook Inlet, Alaska (USA), from 2016 to 2019. Compared historic data (1995-1999), observed declines increased variability productivity across species colonies, predation was widespread. At Chisik, where food limitations were studies, both experienced substantial population failures all 4 years (2016-2019) heatwave. Gull, typically productive failed fledge chicks for 3 (2016-2018) By 2019, recovered about half that studies (0.28 vs. 0.54 per pair), but populations had declined half. Kittiwake size quarter counts, reproduction alternated between complete breeding (2016/2018) high (2017/2019). These multi-year demographic impacts indicate lingering effects heatwave on through fish depletion predator disturbance, possibly other stressors. It remains unknown whether can rebound levels. If so, would likely take decades.