Seabird populations across vast stretches of the Pacific and even into Antarctic waters are collapsing under a combination of ocean warming and infectious disease that scientists had not previously seen converge at this scale. The die-offs span hemispheres, linking a devastating marine heatwave along North America’s west coast to the arrival of highly pathogenic avian influenza in one of Earth’s most remote regions. What emerges is a pattern in which environmental stress and viral spread compound each other, producing mortality events that exceed anything in the modern record for these species.
The Blob and the Collapse of Common Murres
Between 2015 and 2016, an anomalous mass of warm water in the northeast Pacific, widely known as “The Blob,” disrupted the marine food web from the Gulf of Alaska to the California coast. Common murres, diving seabirds that depend on dense schools of forage fish, were among the hardest hit. The warm water shifted prey species deeper or farther offshore, effectively starving birds that had evolved to hunt in cold, nutrient-rich upwelling zones. The result was not a gradual decline but a sudden, visible catastrophe: dead and emaciated murres began washing ashore in numbers that overwhelmed volunteer beach survey networks.
The federal monitoring program for Alaska’s coasts documented more than 62,000 Common Murre carcasses recovered from California to Alaska during the event. That figure almost certainly represents a fraction of total losses, since carcass detection rates on remote coastlines are low. Entire breeding colonies experienced reproductive failures in the seasons that followed, meaning the population could not quickly replace the adults it had lost. The combination of mass adult mortality and failed nesting created a demographic hole that biologists are still tracking years later.
How Starvation Rewrites the Rules for Wildlife
A key detail that often gets lost in coverage of marine heatwaves is the biological mechanism connecting warm water to dead birds. The Blob did not kill murres through heat exposure. It killed them by reorganizing the food web. When surface temperatures rise, the tiny zooplankton and larval fish that support forage species like capelin, sand lance, and juvenile pollock either decline or shift location. Murres, which can dive more than 100 meters but still need prey concentrated within a reachable range, burn more energy searching and catch less. Adults that cannot meet their caloric needs abandon nests. Chicks starve. The starvation cascade moves through the colony in weeks.
This matters for anyone who follows fisheries, coastal economies, or climate science because murres are what ecologists call indicator species. When murre colonies fail, the signal is that the mid-trophic layer of the marine food web is under severe strain. That same layer supports commercially important fish stocks, marine mammals, and other seabirds. The murre die-off was not an isolated wildlife tragedy. It was evidence that the productive capacity of a large ocean region had temporarily collapsed, with ripple effects that touched fishing communities from Kodiak to Monterey.
Avian Influenza Reaches Antarctica
While the Pacific was still absorbing the aftershocks of The Blob, a different threat was advancing through the Southern Hemisphere. Highly pathogenic avian influenza, specifically the H5N1 clade 2.3.4.4b strain, had been spreading through wild bird populations in South America. By 2024, the virus had reached Antarctica. Researchers performed sequencing and phylogenetic analysis on samples collected from brown skuas on James Ross Island, confirming the presence of the strain in a region that had been largely shielded from global influenza circulation by its geographic isolation.
The genomic work, published in the CDC journal Emerging Infectious Diseases, traced the likely introduction route of H5N1 clade 2.3.4.4b to Antarctica via South America. That finding is significant because it demonstrates how migratory bird networks can carry lethal pathogens across hemispheric boundaries, even into ecosystems that lack prior immune exposure. Brown skuas are predatory seabirds that scavenge penguin colonies and interact with multiple species, raising the possibility that the virus could spill over into penguin populations and other Antarctic wildlife with no evolutionary history of H5N1 exposure.
When Heat and Disease Converge
The most unsettling dimension of these events is their potential overlap. Marine heatwaves weaken bird populations through starvation and reproductive failure. Weakened populations are, in turn, more vulnerable to infectious disease. While no single study has yet quantified the combined effect of ocean warming and H5N1 on the same seabird colony, the two threats are operating on the same species groups across connected ocean basins. Murres, skuas, terns, and albatrosses all migrate long distances and congregate in dense breeding colonies, exactly the conditions that favor both starvation cascades and rapid viral transmission.
The genomic evidence from James Ross Island suggests that H5N1 clade 2.3.4.4b is not confined to temperate latitudes. It is moving into polar regions where bird colonies are enormous and tightly packed. If a marine heatwave event similar to The Blob were to coincide with an H5N1 outbreak in the same population, the mortality could dwarf what was observed in the 2015 to 2016 Pacific die-off. That scenario is not a certainty, but the building blocks are now in place: warming oceans, a globally mobile virus, and seabird populations that have not yet fully recovered from prior losses.
Gaps in Monitoring and What They Cost
One persistent problem is that global wildlife monitoring remains patchy. The U.S. Fish and Wildlife Service maintains one of the more detailed surveillance programs for seabird mortality in Alaska, yet even that effort relies heavily on volunteer beach surveys and periodic colony counts. In the Southern Hemisphere, systematic monitoring of avian influenza in wild birds is far less developed. The CDC study on Antarctic skuas represents a snapshot, not a continuous surveillance stream. Without sustained genomic sampling across migratory flyways, scientists cannot track how quickly the virus is evolving or whether new reassortant strains are emerging in mixed-species colonies.
The practical consequence is that the scientific community often learns about crises only after they have reached extreme levels. During The Blob, carcasses accumulated on accessible beaches while many more likely sank unseen at sea. In Antarctica, the first confirmed H5N1 detections came from a small number of sampled birds, leaving open the question of how widespread the virus already was by the time sequencing results were published. These blind spots delay management responses, obscure the true scale of mortality, and make it harder to identify which colonies or species might still be relatively intact and therefore most critical to protect.
What Comes Next for Seabirds and the Seas They Signal
Taken together, the murre die-off in the northeast Pacific and the arrival of H5N1 in Antarctica point to a future in which seabird populations are squeezed from multiple directions. Climate-driven marine heatwaves are projected to become more frequent and intense, increasing the likelihood of further starvation events. At the same time, highly pathogenic avian influenza has shown an ability to move rapidly through wild bird networks and establish itself in new regions, including polar environments once considered buffered from such outbreaks. The convergence of these pressures means that conservation strategies built around single threats—protecting nesting habitat, for example, or regulating fisheries—will not be enough on their own.
Researchers and wildlife managers are increasingly arguing for integrated approaches that treat seabirds as sentinels of broader ocean health. That could mean pairing colony monitoring with oceanographic data to anticipate when heat-driven food shortages are likely, while also expanding viral surveillance to detect H5N1 or other pathogens before they become entrenched. It could mean designing marine protected areas that account not only for breeding sites but also for key foraging zones that may shift as oceans warm. Above all, it means recognizing that the fate of murres, skuas, penguins, and other seabirds is tightly bound to the physical and biological changes unfolding across entire ocean basins—and that their survival will depend on how quickly human societies respond to those changes.
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*This article was researched with the help of AI, with human editors creating the final content.
