Shy albatross Thalassarche cauta chick mortality and heat stress in a temperate climate

With increasing air temperatures and frequency of extreme weather events predicted under climate change, ground-nesting seabird chicks are vulnerable, enduring months at a fixed and often completely exposed nest site, with limited behavioural capacity to reduce heat load. Endangered shy albatross Thalassarche cauta breed in temperate southern Australia, a region warming at about 4 times the global average. We used a remote-monitoring camera to obtain the daily status for ~150 nests each season for 7 seasons (2014-2015 to 2020-2021; 1036 nests in total), allowing clear determination of the date of chick death. We explored local weather conditions associated with chick mortality. We observed 68 downy chick deaths (55%) across a 30 d period in 2018. This period corresponded with anomalously high and prolonged wet bulb temperature, an index for heat stress. We show that shy albatross breeding attempts are vulnerable to hot weather conditions and define extreme heat stress conditions for this species (>20° wet bulb temperature). Documenting the relationship between chick survival and heat before future catastrophic events occur gives managers time to plan for future heatwaves by developing climate adaptation strategies for seabird populations.