Seabird range contraction and dispersal under climate change

Many marine ectotherms have historically adapted to local climate change by evolving smaller body sizes, reducing their energy demands in warmer waters but limiting their dispersal and speciation rate. Whether endothermic marine species respond similarly remains unclear, as temperature minimally affects their size diversity, and the drivers of their dispersal and speciation are poorly understood. Here we show that globally distributed seabirds (albatrosses, petrels, shearwaters, and storm petrels), facing rapid historical climate change, responded by shifts in geographic range size rather than body mass. Additionally, where the rate of warming is high, geographic ranges contracts most, intensifying the selective forces for higher dispersal capacity, and increasing speciation rate. Our findings reveal a triple threat to extant seabirds from human-induced global warming: shrinking ranges increase their extinction risk, push them to their maximum limit of dispersal capacity, and subject them to unprecedented warming rates. These insights reveal a distinct endothermic response to ocean warming, underscoring the vulnerability of seabirds and the urgent need to integrate range dynamics into conservation strategies for marine biodiversity under accelerating global change.