Guest Post: Documenting a Seabird Die-Off

This post was contributed by Robin Corcoran, author of a paper in the current issue of the The Wilson Journal of Ornithology documenting the Common Murre die-off described here.

Dead Common Murres found on the beach at the head of Pasagshak Bay, Kodiak, Alaska, on September 10, 2015.

As a bird biologist with the U.S. Fish and Wildlife Service in Kodiak, Alaska, I’m used to getting reports about dead and injured birds in our region from the public. Part of my job is to track these reports and investigate and collect carcasses. So, I wasn’t alarmed at first when I received scattered sightings of a few dead Common Murres in April and early May 2015. I collected a few of the intact fresh carcasses and stored them in the biological specimen freezer at Kodiak National Wildlife Refuge, and then the reports stopped.

In June 2015, my field crew and I headed out to conduct nearshore marine bird and mammal surveys along approximately 2,000 kilometers of remote shoreline at the northeastern end of the Kodiak Archipelago. We had last surveyed this region encompassing Afognak, Raspberry, and Shuyak Islands in 2012. We immediately noticed that we were seeing a bird species everywhere that had not been very common during the 2012 surveys – the Common Murre.

On these surveys, we count all the birds we see from our small skiff as we travel on transects along the coastline and offshore. We collect the data using a rugged laptop with specialized software for marine bird surveys. This software allows us to rapidly enter data as we survey with “hotkeys” that we can set up based on the most abundant species recorded on previous surveys. The crew just kept asking me: why isn’t the Common Murre a hotkey?

Weak Common Murres with ragged plumage seen on the Kodiak Refuge marine bird survey of the Afognak-Shuyak Island region in August 2015.

We repeated the survey transects in August 2015, just as we had done in 2012. We added Common Murre as a hotkey since we continued to see that species in very high numbers along the coast. It’s hard to describe just how many more Common Murres we were seeing. During our survey three years before, we counted fewer than 300 Common Murres and saw only six percent of these birds on transects within 400 meters of shore. In contrast, we counted 8,000 Common Murres on those same transects in 2015 and saw 57% of them on nearshore transects.

Despite seeing so many murres and hearing reports from other regions of Alaska about a seabird die-off, we only found six dead murres while on the survey in June and August. However, many of the murres we saw had ragged plumage and swam along listlessly, eyes closed, barely moving out of the way of our skiff. We also witnessed a behavior we had not seen in previous years: single or small groups of Common Murres standing onshore, most asleep. As we observed their strange behavior and ragged plumage, we began to realize that the murres were in trouble.

Weak, emaciated Common Murre found on the beach at the Buskin River State Recreation Area, Kodiak, Alaska, on October 15, 2015.

In some previous seabird die-off events, people have anecdotally reported seeing an increasing number of birds that are normally found far offshore moving into the nearshore zone. Our recent publication in the WJO is one of the first to quantify the magnitude of such an increase prior to a widespread mortality event.

In mid-August, people around the city of Kodiak started noting unusual Common Murre behaviors, including weak birds standing on rocks or the beach. Many of these birds did not attempt to flee when approached. As the month progressed, more and more Kodiak residents posted on social media about finding sick and dead murres on many beaches. Reports of dead birds peaked between August 21 and September 7, 2015.

Dead Murres found on the beach at the head of Kalsin Bay, Kodiak, Alaska, on November 17, 2015.

Alaska’s vast amount of inaccessible remote coastline makes it challenging to monitor a seabird die-off. In Kodiak we had a unique opportunity to regularly survey a relatively large selection of beach segments along the road system, a network of about 225 kilometers of road connecting the city of Kodiak with outlying communities clustered at the northeastern end of Kodiak Island. Ultimately, we ended up completing 160 surveys along 23 beach segments of the Kodiak Island road system from May 8, 2015 to April 26, 2016. Observers found dead murres on all but one of the beaches searched.

We recorded 786 carcasses representing 16 bird species. The vast majority of carcasses (92%) were Common Murre, followed by Crested Auklet (3%), a species that regularly winters in offshore waters of the Kodiak region. Using data from the beach surveys, we estimated that 6,305 dead Common Murres washed up along the Kodiak road system during the survey period.

Reports of incidental observations of 1,275 dead Common Murres from outside of the surveys, mostly from remote areas throughout the archipelago, also came to the refuge. These reports gave us a window into a widespread regional murre die-off. Seven observations exceeded 100 dead birds on a single occasion, including an estimated 300 dead murres along a 5 kilometer stretch of beach at the mouth of the Ayakulik River at the western end of Kodiak Island in mid-August 2015.

Researchers have called the 2015–2016 Common Murre die-off unprecedented in both the vast area it covered and the many months it persisted. So many of the people who reported seeing dead birds asked the same question: why was this happening?

Dead Common Murre (and salmon) found on the beach at the head of Kalsin Bay, Kodiak, Alaska, on September 10, 2015. 

Many previous seabird die-off events in western Alaska occurred in association with warm sea surface temperatures. The die-off of 2015–2016 occurred during the largest recorded marine heatwave in the northeast Pacific, with a record of sea surface temperature three to eight degrees Celsius higher the mean in the Gulf of Alaska. Researchers think that the prolonged warm surface temperatures impacted fish both above and below the seabirds in the marine food web, described as an “ectothermic vise.”

I’m happy to report that when we repeated our marine bird survey of the northeastern end of the Kodiak Archipelago in June and August of 2021, , Common Murres numbers had returned to 2012 levels. As we drove our skiff along the nearshore transects, we no longer needed a hotkey to log Common Murre sightings, since that species was infrequently seen relative to our much more abundant gulls, murrelets, and puffins. I’m also relieved that since the die-off, I rarely encounter a dead bird on my daily hikes of Kodiak’s local beaches.

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About Wilson Ornithological Society

The Wilson Ornithological Society (WOS) is an international scientific society comprising community members who share a curiosity about birds. The WOS produces the quarterly Wilson Journal of Ornithology as the latest iteration of scientific journal publication supported by the Society since 1888. The WOS is committed to providing mentorship to both professional and amateur ornithologists through sponsorship of research, teaching, and conservation. Find us on wilsonsociety.org, Facebook, Twitter, and Instagram (@WilsonOrnithSoc).

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