A study published by US Fish and Wildlife Service biologist Heather Renner reveals that the 2014-2016 “Blob” marine heatwave, which killed an estimated 4 million common murres, had a lasting impact on the species. The population has not recovered seven years later, with biologists describing the effect as “catastrophic.”
The Blob was particularly devastating for common murres, which are among the most abundant seabirds in Alaska. Prior to the heatwave, there were approximately 8 million common murres in the state, but about half of them died within a year.
Renner attributes the high mortality rate to the fact that common murres have “high energetic demands” due to their deep-diving and large size, requiring them to eat about half their body weight daily. The heatwave disrupted the availability of forage fish that school in dense groups, making it impossible for the birds to adapt.
Thick-billed murres, a related species, were less affected by the heatwave, as they have more flexible prey options and are better equipped to cope with changing conditions.
The ongoing impact of the die-off is hindering recovery efforts. Thinly populated colonies lack the defense mechanism of massing together to protect nests from predators like eagles, making them vulnerable to threats.
In contrast to a previous oil spill in 1989, which resulted in an estimated 250,000 bird deaths and a partial recovery for the common murre population, Renner expresses concern that Alaska’s population may not recover due to repeated heatwaves predicted by climate change.
Source: https://www.chilkatvalleynews.com/2024/12/23/alaska-birds-suffered-biggest-die-off-in-recorded-history-in-blob-heat-wave-new-study-says