By Will Kennerley, Faculty Research Assistant, OSU Seabird Oceanography Lab
The 19th consecutive year of Yaquina Head monitoring is upon us. A local naturalist, Chris Fox, first reported murres occupying Colony Rock in mid-March but the returning murres were met with Bald Eagle disturbances almost immediately. While eagle disturbance likely contributed to the rather sporadic murre attendance throughout April and May, it seems that delays in upwelling (or at least a delay in consistent upwelling?) likely limited seabird breeding activity during the spring. While I’m still waiting for more formal, quantitative summaries of spring ocean conditions here, we observed warmer sea surface temperatures (12°C/54°F) off the central coast during much of May. During this time, we witnessed murres and cormorants attending the colony, but only half-hearted cormorant nest building on May 21st, the date on which we had our first Brandt’s eggs the year before.
Then, during the last week of May, the satellite maps I was monitoring began to show plumes of cool water moving northward from the California line. Sea surface temperatures dropped below 10°C/50°F close to the coast, suggesting the onset of strong upwelling and, presumably, increased ocean productivity. With surprising speed and synchronicity, we noted both of our cormorant species and murres quickly began nest building and/or egg-laying. By the first week of June we had our first Brandt’s Cormorant and Common Murre eggs, and our first Pelagic Cormorant eggs were laid before June 11th.
This level of synchronicity was exciting to see and stands in stark contrast to observations over the last few years. In 2024, Pelagic Cormorant breeding phenology was several weeks behind that of Brandt’s, while in 2023 both cormorant species were closely synced but they were a month or more ahead of the Common Murres! The reasons behind the highly variable breeding phenology are likely a complicated mix of ocean conditions and predation pressure, with the timing of murre egg laying regularly more aligned with Brandt’s Cormorants at our less eagle-disturbed site in Depoe Bay. This year, however, murres even at Yaquina Head seem to be laying eggs in sync with both cormorant species, and are doing so at dates closer to (though still later than) historical norms.
Now that we’re into the middle of June, most seabirds at our sites are busily incubating full clutches. Eagle disturbances continue but so far appear to be comparatively mild, with fewer whole colony-clearing disturbances observed. Still, eagles have regularly swept murres from the south end of Colony Rock and Flat Top, and we’ve rarely observed eggs at these exposed sites persist more than a few days. Elsewhere, such as our Lower Colony Rock and Whale Rock subcolonies, which offer more protection against aerial predators, some murres have been incubating for over a week already; this means that we could have murre chicks by July 10th, if all goes well! The first Western Gull chicks, meanwhile, have already begun to hatch, and visitors should keep an eye out for fuzzy, speckled heads poking up from the stones and sparse grasses atop Colony Rock.
Our lab also just welcomed a new set of interns and research assistants for the summer – Caitlin (NSF-REU), Cherish (OSU undergraduate), and David (EFTA intern at BLM’s Yaquina Head Outstanding Natural Area). It’s always convenient when the bird’s breeding phenology aligns well with OSU’s quarter system, and I’m hopeful our full team will get to observe the complete egg to fledgling progression! Although it’s early days, the strong, synchronized reproductive effort, relatively mild eagle disturbances, and regular appearance of rockfishes and large sandlance in murre bills (as display fish), all give me hope that our breeding seabirds have a successful season ahead of them.
More to come!
