Knowledge of seasonal marine bird migration patterns is required to inform marine bird conservation and management efforts. We deployed solar-powered satellite transmitters to track the movements of threatened marbled murrelet Brachyramphus marmoratus during the breeding and post breeding periods. We tagged birds (n = 27) in British Columbia (BC), Canada, over 3 years (2014-2016) from 3 different marbled murrelet conservation regions as defined by the species’ recovery strategy. Of 4 tagged birds which provided movement data for more than 57 d, 3 (1 in each year) revealed long-distance movements from BC to Alaska, USA, during breeding or post-breeding periods. The 3 birds which moved northward originated from the 3 different conservation regions. We found limited support for the concept that birds tracked cooler waters as they headed northward. One bird remained in unusually warm waters near the capture sight in Desolation Sound in 2016. Importantly, the arrival of BC birds in Alaska during summer could contribute to at-sea survey estimates of marbled murrelet abundance during the Alaska breeding season, and their occcurence in Alaska has implications for BC populations with respect to anthropogenic threats in the marine habitat, including the potential for incidental take in gillnet fisheries and risks from oiling. Our results demonstrate connectivity between BC and Alaska marbled murrelet populations. Overall, tracking duration was relatively short, and locations were confined to the deployment areas in BC. Our results indicate capture and tagging impacted study individuals and may have contributed to increased mortality. Our research, coupled with that of others, suggests that long-distance northerly migrations patterns may not be unusual in Brachyramphus murrelets.

Acute anomalous ocean warming events, including marine heatwaves (MHWs), have significant effects on reproduction and survival of piscivorous seabirds. Additionally, MHWs have negative effects on seabird fish prey, exacerbating these consequences and resulting in population implications for seabirds. We evaluated the relative body condition of Pacific sand lance Ammodytes personatus, an important seabird forage species, in Haro Strait, a highly productive region of southern British Columbia, Canada. We compared body condition and length of fish cohorts that experienced the 2016 MHW year (MHW cohorts) with fish hatched during 3 subsequent post MHW years (2017-2019). Age-0 MHW cohorts had a seasonal decline in body condition in age-0 fish from 100% in the summer to 81% in the winter, while age-1 fish showed a decline from summer-fall highs of 93.5% to wintertime low of 79.5%. In comparison, post MHW cohorts had a winter body condition that was 2-4 times higher than their MHW cohorts. Similar to previous studies in Alaska during the MHW, age-1 fish failed to grow and reach the typical size that distinguishes them from age-0 fish. Poor sand lance condition and growth in winter may explain the ramifications of a warming ocean for top predators, including seabirds and Pacific salmon, which depend on these prey fish in Haro Strait. Our results support the idea that Haro Strait, which is influenced by estuarine circulation resulting in cooler temperatures than surrounding areas, serves as a climate refugium for sand lance populations in summer and provides buffering capacity to ocean climate warming events.