Los Farallones

Dispatches from Point Blue’s field station on the Farallon Islands National Wildlife Refuge

Record-setting Heat on the Farallones

When you sign up for an internship on Southeast Farallon Island, you have certain expectations. The weather should vary from warmish to cold, kinda windy to super windy, mellow seas to raging waters.
Then one morning you step outside, jacket on, ready for action, but something is wrong. It’s 6:45 and you are immediately hot in your jacket. The breeze seems absent. You check the thermometer; it’s already 64.5 degrees F and rising. On September 2nd, along with the rest of California, the Farallones experienced a heat wave, and as was the case in many other localities, records were set. At 10:55 AM we documented 31.5 degrees C, or 89 degrees F, the highest temperature ever seen on Southeast Farallon Island since Point Blue’s daily weather records began in 1968.
The pinnipeds knew what to do. California Sea Lions poured into the water in massive numbers, leaving large parts of the island temporarily unoccupied for the first time since I arrived. A pinniped census conducted the day before (also a scorcher) had almost 2000 fewer sea lions than were hauled out on the island a week before, a 39% decrease. Northern Fur Seals declined by 55% and could be seen filling the bay in front of Indian Head Beach, forming one massive raft. Northern Elephant Seals and Steller Sea Lions were thin on the ground, seeking the cooler water.
Birds cannot sweat, and birds on the island were showing obvious signs of heat stress. Everywhere I went Western Gulls stood with their beaks gaping, letting heat escape. Brandt’s and Pelagic Cormorant nestlings were madly flapping the skin at their throat, or gular, pumping air across that thin membrane of skin to rid themselves of unwanted heat.
While the resident birds were trying to stay cool we had a handful of migrants passing through during the heat wave. A Mourning Warbler arrived on the first, along with 4 Black Swifts and a Barn Swallow flying over. The second brought us a Yellow-Breasted Chat, Brewer’s Sparrow, Pine Siskin, Barn Swallow, and a record high-count for a day of 6 Black Swifts flying over.

Mourning Warbler
Mourning Warbler

On the Farallones, we use nest boxes to monitor Cassin’s Auklet nesting success. Up until the last few years, we did not experience severe heat waves on the Farallones during the nesting season. To prevent auklets from overheating in this increasingly warm climate, we have built shade structures for our older wooden nest boxes, and designed new ceramic boxes that can withstand the heat. Lauren Lescure, the seabird carryover intern from the summer, ensured that shade structures were in place and piled dead vegetation on top of boxes to increase shade cover and insulation. All of the auklets survived the day.
image (2)     image (1)
Cassin’s Auklet Nest Boxes

Behavioral responses to a warm day are all well and good if this was a one-time occurrence, but weather data that Point Blue has collected on the island over the last 46 years reflect current climate change models: increasing peak temperatures over time. This leads us to consider what possible evolutionary responses birds will express in response to climate change. Extreme heat and weather events can kill birds, and birds are adapting to climate change by changing breeding and wintering ranges, changing migration timing, and changing body size. Point Blue researchers, using data collected at Southeast Farallon Island and the Palomarin banding station are showing changes in body size correlating with climate change.
Alas, my response to the hottest day recorded on the island was less than clever. It was my turn to make dinner, and I got it in my head to bake a fresh apple pie and cook risotto over the hot stove. Did the island kitchen reach a new high temperature? Without historic records we will never know.