By Hannah Motta, Environment for the Americas Intern at Yaquina Head Outstanding Natural Area
Although it’s not the typical rainy season that signals the end of summer here, we officially wrapped up our Yaquina Head field season on the morning of August 16th. My name is Hannah, and I’m an Education and Outreach Intern with Environment for the Americas, stationed at Yaquina Head. I recently graduated from the University of Oregon with a B.S. in Environmental Science and a B.A. in Spanish, where I focused on environmental education. My goal has always been to inspire people to care about nature through birds, which ultimately brought me here to Yaquina Head.
In my current role, I work as an interpretive park ranger and assist our facilities operations manager on the maintenance team at Yaquina Head Outstanding Natural Area. Throughout the summer I assisted Oregon State’s Seabird Oceanography Lab in monitoring cormorant, gull, and murre colonies at Yaquina Head and Depoe Bay.
As we predicted in our earlier posts from this spring, this year was a “bust” for Pelagic Cormorants, while Brandt’s Cormorants had a much more positive outcome. The Common Murres, however, experienced dramatically different results between Yaquina Head and Depoe Bay, largely due to high rates of Bald Eagle predation. As you may have noticed throughout this season, Bald Eagles have taken center stage as some of the main characters.
Since most people prefer to get the bad news out of the way first, let’s start with what happened—or more accurately, what didn’t happen—with the Murres at Yaquina Head. Frequent eagle disturbances caused the Murres to flush for hours at a time, leaving very few eggs laid in visible areas. Of the nests we were able to observe, we followed 38 across three different plots. Out of those 38 nests, only two eggs successfully hatched and fledged. A few Murre chicks may have taken shelter in the nooks and crannies of Whale Rock to avoid predation, but overall, we were left with a mere 5% reproductive success rate—a somber finale for the Murres at Yaquina Head.
Now for the much happier news from Depoe Bay! With far fewer eagle disturbances, the Murres had a much better outcome. We monitored 75 Murre nests across five plots, and an impressive 93% of all chicks survived to fledge! Throughout the year, we documented adults bringing back lots of smelts, flatfishes, and sandlance to their chicks, likely fueling the high fledging success rates we witnessed.
And yes, as I mentioned earlier, the eagles were causing quite a bit of drama this year. They even managed to prey on some adult cormorants and chicks, which we don’t typically observe. Back at Yaquina Head, we tracked the progress of 27 Pelagic Cormorant nests and 45 Brandt’s Cormorant nests.
The Pelagic Cormorants nested nearly two weeks later than usual at Yaquina Head (long-term average hatch date: July 11th; 2024 median hatch date: July 28th) later than usual and had low reproductive success. Only 15 of the 27 nest structures visible at Yaquina Head had eggs, and these had an average clutch size of 2.7 eggs per nest. Sadly, only 12% of those eggs hatched in late July, and only two nests managed to fledge chicks.
But here’s the good news! The Brandt’s Cormorants had a much more successful season. Out of 45 nests monitored, eggs were laid in 37, with the average clutch size being a very respectable 3.1 eggs per nest. On average, each nest fledged 2.1 chicks, which is well above the long-term average, though slightly lower than last year’s record-breaking 2.4 chicks per nest.
Interestingly, despite variable eagle predation between our two sites (typically high at Yaquina Head, low at Depoe Bay) our cormorants did very similarly at both colonies. Although we observed a few instances of eagles preying on cormorant chicks at both sites, it appears the impact this predation had on cormorant nesting success was either minimal, or more even between sites than disturbance to murres was. We’ll have to watch out next year to see if eagles continue to prey on cormorant chicks and these birds will face any population-level impacts like cormorants in British Columbia have in recent decades (Carter et al. 2018).
The 2024 seabird monitoring season at Yaquina Head was a mixed bag; while we observed poor reproductive performance for both Pelagic Cormorants and Common Murres, the Brandt’s Cormorants had a great season. What’s more, the Depoe Bay Murres thrived, seemingly unaware of the struggle their conspecifics faced just ~15km south! But now, both colonies appear starkly quiet and empty; it’s time to start looking forward to the day the rocks and cliffs are covered by breeding seabirds once more.
I’d like to thank you all for your support of the Yaquina Head Seabird Monitoring Program and want to extend a huge thanks to the amazing team I had the opportunity to work with—Aya, Travolis, and Will. You all made getting up extremely early and standing in the cold by far some of my favorite memories this summer.
Thanks for keeping up, and see you all next year!
