To Breed or Not to Breed

Yaquina Head Early Season Update, Summer 2024

It’s the start of another summer on the Oregon Coast and I once again find myself spending most mornings out on rocky headlands for another season of seabird monitoring. Since early May, I’ve been following the breeding activities of murres, cormorants, and gulls at Yaquina Head (Newport) and Pirate Cove (Depoe Bay). As the season begins to take shape, I wanted to share what I’ve been seeing through my spotting scope.

Initial signs are mixed, but seemingly point to a year of low to moderate breeding success for most species. Common Murres have been around the two colonies for months by now, yet occupation of nesting sites has so far only been sporadic. I’ve yet again been observing frequent disturbances by up to four bald eagles at a time, which has prevented the murres from regularly settling into the colony and their nest sites (Figure 1). Because of the frequent eagle activity, I’ve rarely had the opportunity to see murres fully occupy all the Yaquina Head subcolonies; my best guess, however, is that the number of murres attending the colony is lower than at this time last year.

Despite regular disturbances, I observed the first few murre eggs at Yaquina Head on June 6^th! While these eggs were predated within a few days, this does indicate that murres are willing to attempt breeding and I suspect more eggs will be seen soon. The ability of murres to breed successfully last year, despite heavy eagle disturbance early on, gives me reason to be cautiously hopeful that at least some Yaquina Head murres will manage to fledge chicks this year. Eagle disturbances appears to be fewer and less severe at Pirate Cove, and I’m eager to see how long the first few murre eggs at that colony persist. Despite the challenges imposed by eagles, murres appear motivated to attempt breeding.

Figure 1. One of several subadult Bald Eagles frequently seen disturbing the seabirds breeding at Yaquina Head, Oregon.

In contrast, Pelagic Cormorants are by and large not attending either the Yaquina Head or Pirate Cove colonies this year. Last summer saw record-high Pelagic Cormorant productivity and each monitored nest fledged an average of 2.8 chicks; however, so far this summer, I’ve only been able to locate a single nest with eggs across our two sites.

Cormorants, generally – and Pelagics, in particular – are known for highly variable reproductive outputs (Figure 2). Some seabirds (e.g., tubenoses) take more of a “low and slow” approach to reproduction that leads to a moderate but fairly consistent output across years, but Pelagic Cormorant reproduction is typified by highly variable, “boom or bust” cycles. Ainley and Boekelheide note in their Seabirds of the Farallon Islands (1990) that Pelagic Cormorants experience the most extreme interannual variation in breeding effort and success of all the seabird species that breed there. Cormorants are sensitive to fluctuations in prey populations and may skip breeding when prey is scarce, but they can also lay large clutches to take advantage of highly favorable conditions.

While 2023 was undoubtedly a “boom” year, 2024 is shaping up to be the accompanying “bust”. Initial monitoring of many well-built nests saw birds abandon nest-guarding early on and relatively few Pelagic Cormorants even appear to be attending the colony. Cormorant reproduction in the California Current System is related to sea surface temperature, with low reproductive effort often associated with warm-water, El Niño periods (Schmidt et al. 2015) like we experienced this last winter.

Figure 2. Pelagic Cormorant productivity at Yaquina Head from 2008-2023. Reproductive output from this species is highly variable between years.

Brandt’s Cormorants (Figure 3), on the other hand, are attempting to breed this year at both sites. Most are busily incubating three or even four egg clutches now, with the first chicks expected by the end of June. It’s possible that Brandt’s Cormorants finished the winter in better body condition than Pelagics, perhaps because they often exploit different foraging habitats and prey types (Ainley et al. 1981). Brandt’s Cormorant reproduction does tend to be somewhat less variable than that of their cliff-dwelling relatives (Ainley & Boekelheide 1990), but still varies considerably between years in relation to ocean conditions and prey abundance (Schmidt et al. 2015; Ainley et al. 2018). It’s interesting to observe these two congeneric species of seabird respond so differently to these conditions. However, cormorants may also abandon breeding efforts mid-season if prey availability should suddenly decline, so I’ll continue monitoring to see how the Brandt’s manage to do this summer.

Figure 3. Brandt’s Cormorant males spend lots of time collecting nesting material. Breeding Brandt’s were frequently seen collecting grasses from the headland at Yaquina Head, as well as stealing material from their neighbors’ nests.

As for other species, Western Gulls have been faithfully incubating their two and three egg clutches at both sites for several weeks now – it’s just a matter of time before our first downy chicks of the year are around. The Black Oystercatchers aren’t nesting at easily-visible sites this year, but their raucous calls continue to be a near-constant presence at both colonies. Excitingly, I’ve also observed Tufted Puffins circling the Yaquina Head murre colony on several occasions, and once saw one flying over Pirate Cove! While neither site has much suitable nesting habitat for puffins, the USFWS recently placed puffin decoys and artificial burrows on Gull Rock (located squarely between the Yaquina Head and Pirate Cove colonies) to draw them there. The puffins’ continued interest in these sites continues to raise my hopes that one day soon we’ll have Tufted Puffins nesting again on the Central Coast.

So far, it seems challenging to predict just what kind of year we’ll see on the Oregon Coast. Reduced breeding effort by Pelagic Cormorants and (to a lesser extent) murres, suggests unfavorable conditions. Yet, murres (though perhaps in somewhat lesser numbers) have begun to lay eggs at both sites and Brandt’s are attempting to breed in seemingly typical numbers. I’ll continue to brave the wind and fog to document how this annual drama plays out.

References

Ainley & Boekelheide. 1990. Seabirds of the Farallon Islands: Ecology, Structure, and Dynamics of an Upwelling System Community. Stanford University Press, Stanford, CA, USA.

Ainley et al. 1981. Feeding ecology of marine cormorants in southwestern North America. The Condor 83: 130-131. https://doi.org/10.2307/1367418

Ainley et al. 2018. Ecosystem-based management affecting Brandt’s Cormorant resources and populations in the central California Current region. Biological Conservation 217: 407-418. https://doi.org/10.1016/j.biocon.2017.11.021

Schmidt et al. 2015. Shifting effects of ocean conditions on survival and breeding probability of a long-lived seabird. PloS ONE 10(7): e0132372. https://doi.org/10.1371/journal.pone.0132372

September 26, 2023September 26, 2023

Yaquina Head Monitoring Update: the end of the 2023 season

As we’re enjoying the first major rains of the fall here on the Oregon Coast, we now have another year of Yaquina Head seabird monitoring in the books (and the latest one to date)! We wrapped up our Yaquina Head field season on the morning of September 6^th after the fledging or loss of the last murre chicks remaining in our plots.

For the seabirds as a whole, it was certainly an odd year, but not necessarily a bad one. After a poor 2022 season, the pelagic and Brandt’s cormorants did very well at Yaquina Head, with most nests fledging multiple chicks. In contrast, initial prospects for successful murre reproduction seemed poor. The eagles and attending secondary predators hammered the murres early on: we documented nearly 22 hours of eagle-related disturbances, witnessing a minimum of six murre adults and 73 eggs consumed during this time. Considering that we only monitored the Yaquina Head colony three mornings a week, the total number of eggs predated must have been exponentially higher.

Almost without warning, however, the eagles moved on and the persistent murres were ready to exploit this reprieve. As mentioned in our last update (emailed 08/23/23), this summer we recorded the latest median murre hatch date since monitoring began at Yaquina Head. One consequence of this is that by the time the eagles moved on, and eggs began to persist for longer than a day or two, most murres had already attempted to breed. It’s not likely that some murres even re-laid eggs, only to lose their egg to the gulls a second time! Reproduction is costly for murres and by the time conditions were good, most individuals had already given up and decided to save their finite energy resources for overwinter survival and (hopefully) next year’s nesting attempt.

Unfortunately, we don’t have multiple, complete colony counts documenting the decline in breeding murre numbers throughout the season, but we can use photographs to get a rough, qualitative understanding of this decline in colony size. Compare these photos: both were taken during the middle of chick-rearing, one showing the “full” colony (circa 2017), while the other is from early August 2023. By mid-summer, the number of murres raising chicks on Colony Rock this year was clearly just a fraction of what we once observed.

Two photos (2017 and 2023) show the disparity in numbers of breeding murres at Colony Rock. Although some murres may have migrated to other colonies (e.g., Pirate’s Cove) in recent years, we believe the main driver leading to a small mid summer colony size was heavy predation pressure leading to early nest loss.

It isn’t all doom and gloom, however. Those murres that laid or re-laid eggs exceptionally late did have a reasonable chance of successfully incubating that egg until it hatched. For example, only 1 out of 3 eggs laid during June survived the marauding eagles, gulls, and crows to successfully hatch. In contrast, more than 2/3 of the eggs laid during July ended up hatching. Once out of the egg, those chicks that did hatch this year did quite well. By the time chicks hatched in late July/early August, the eagles had left the colony alone, and more than 80%* of all hatched chicks survived to fledge.

In sum, although the overall colony size was substantially smaller, and murre egg losses were high until late June, the Yaquina Head colony was able to successfully raise some chicks this year.

Part of this success is surely attributable to this summer’s favorable ocean conditions and prey resources. Our team documented what murre chicks were feeding on by photographing adult murres bringing fish to the colony, and we also recorded the frequency with which these feeds occurred during three, all-day provisioning watches. We observed murres feeding their chicks an average of 3-4 times per day, bringing in lots of smelt (Family Osmeridae), plus lesser numbers of herring or sardine (Family Clupeidae) and sandlance (Family Ammodytidae). These are all relatively nutritious prey items that enabled the surviving murre chicks to grow quickly and to eventually head to sea with their fathers by the beginning of September.

Many (~80%) of the murres that managed to hatch chicks were able to find enough fish to
successfully raise their chick until fledging.

2023 was certainly a roller coaster for the Yaquina Head murres, but the birds displayed incredible persistence. We witnessed heavy predation pressure early on that threatened to lead to another year of complete reproductive failure (like 2022), but the murres displayed great flexibility and managed to lay eggs and raise chicks later than we’ve ever before documented. In spite of all the diverse challenges seabirds face worldwide, their remarkable adaptability continues to give us hope.

Thank you all for the support and continued interest in the Yaquina Head Seabird Monitoring Program. A huge thanks to our hard-working interns this year (Jacque, Neci, and Ricardo) and all the other people who made this work possible. We hope to see you all out at the lighthouse next May!

*please note that exact values may change slightly pending further data proofing and processing

September 1, 2023

Yaquina Head Seabird Monitoring: Mid-Summer 2023

Hello Everybody!

My name is Ricardo Rodriguez, I am the Education and Outreach intern at Yaquina Head Outstanding Natural Area through Environment for the Americas. I recently graduated from the University of California, Merced with a Bachelor’s degree in Biological Sciences. I am assisting Oregon State University’s Seabird Oceanography Lab’s research efforts to monitor the reproductive success of the Common Murres (Uria aalge), Brandt’s Cormorants (Urile penicillatus), and Pelagic Cormorants (Urile pelagicus). I have experience conducting avian point count surveys of urban songbirds in Northeast Los Angeles as a Community Climate Action Corps Fellow, but this my first taste of bird monitoring and nest tracking in my early career. I am very grateful for this opportunity to contribute to this long-term monitoring effort.

Per usual, the Common Murres have had a rocky season on Colony Rock. There were many eggs that were eaten or dropped by Western Gulls (Larus occidentalis) when the voracious Bald Eagles (Haliaeetus leucocephalus) would hunt for Murres. It has been very unfortunate seeing broken Murre eggs along Yaquina Head. Between the first monitored murre egg (June 12th) and our last recorded eagle disturbance (July 17th), we recorded more than 1.1 eagle disturbances per hour of observation and directly witnessed 73 eggs consumed by eagles and gulls during these events. Eagle disturbances and predation of the Murres has have slowed down significantly since the middle of July, thankfully, thus allowing Murres to incubate any eggs that have not been destroyed .

Following disturbances from Bald Eagles, Western Gulls swoop in to feast on unprotected murre eggs. *Photo credit: Ricardo Rodriguez*.

Both adults of a Common Murre breeding pair incubate the egg. The incubation period can take anywhere from 28 to 37 days. The first Murre chick was observed on July 19, 2023 on Seal Rock and this year is likely the latest median hatch date we’ve ever recorded (peak hatch this year was between July 28^th and August 7^th). 2018 was the previous record for latest median hatch date (~July 15^th) at Yaquina Head, so the delay caused by predator disturbance this year was quite significant. As many as 26 Murre chicks have been recorded in our monitoring plots at Colony Rock alone, and we are hopeful to see many more on the other offshore islands that we have been observing.

Better late than never! Median hatch date for murre chicks is the latest we’ve ever recorded at Yaquina Head. *Photo credit: Will Kennerley.*

Adult Murres have been observed and photographed to bring their chicks lots of Smelt (Osmeridae) and Herring (Clupeidae ). We’ve also conducted our first of multiple dawn-to-dusk provisioning watches by which we estimate the rate at which adult murres provision their chicks. We hope to fit in two more of these watches before weekly until more chicks fledge. Some chicks have already fledged and their calls can sometimes be heard from the headland. I have worked at Yaquina Head since the beginning of April; I have clearly seen less and less Murres attending the colony compared to the amount back in May.

Oregon State University PhD student Suzanne Winquist records a murre feeding its chick during one of our dawn to dusk provisioning watches. *Photo credit: Will Kennerley.*

We are nearing the end of our Pelagic and Brandt’s Cormorant monitoring efforts at Yaquina Head Following a total of 55 nests across the two species, we estimated that Pelagic and Brandt’s Cormorants fledged an average of 2.8 and 2.4 chicks per nest, respectively. All in all, we estimated that more than 80% of all cormorant chicks that hatched eventually went on to fledge, among the highest we’ve recorded in the 16 years we’ve been monitoring cormorant productivity.

It has been an absolute pleasure working with an amazing team of researchers. Come visit us out at Yaquina Head!

— Ricky, Neci, Jacque, Mariam, and Will

July 6, 2023July 6, 2023

Yaquina Head Seabird Monitoring: 2023 Early Season Update

By Will Kennerley, Faculty Research Assistant

It’s once again summer on the Oregon Coast and that means the seabirds are back at Yaquina Head. My name is Will Kennerley and I’m the newest faculty research assistant in the Seabird Oceanography Lab. Part of my work will include leading the monitoring fieldwork at Yaquina Head this year. I spent the previous six summers working with seabirds in the Gulf of Maine, including two seasons of fieldwork for my Master’s, which I completed here at OSU in May. I’m looking forward to applying this experience to Oregon’s large and diverse seabird populations.

Monitoring work at Yaquina Head began towards the end of May with the confirmation that Brandt’s and Pelagic Cormorants were both breeding here this year. Pelagic Cormorants failed to breed successfully in 2022, so we were anxious to see how they would perform. Much to our relief, at least 70 Pelagic Cormorant nests have been documented in Smuggler’s Cove, alone, and most have healthy clutches of four eggs.

Our very first Pelagic Cormorant chick was observed on June 23^rd and we’re hopeful that there will soon be many more! As for Brandt’s Cormorants, we recorded our first chick back on June 16^th and most Brandt’s nests so far have at least one hatched chick, with even more on the way! It seems that the cormorants are off to a good start this year.

Most Pelagic Cormorants remain on eggs at the Smuggler’s Cove subcolony at Yaquina Head. The first chicks for this species were noted in late June and many Pelagic Cormorant chicks will likely be hatching out over the next week.

In typical fashion, the situation for the Common Murres is a little less rosy. Starting in the middle of June, murre eggs appeared in a slow trickle that was easily consumed by Western Gulls during the frequent eagle disturbances. There were a couple troubling weeks in which our monitoring team would observe new nests in our monitoring plots during each visit without any of these eggs ever surviving until the following check, just two or three days later.

This situation has improved somewhat during the last week, thankfully, and eggs are being laid in greater numbers; hopefully this bump in egg-laying can overwhelm the marauding gulls and allow some eggs to survive and develop. Overall, I suspect murre productivity will be poor at Colony Rock, where I’ve seen as many six different Bald Eagles roosting at a time, but some of the smaller rocks around Yaquina Head provide better cover for the murres and have thus far avoided most of the disturbances and depredation. Although the season is advancing rapidly, there’s still some time for murres to be at least somewhat successful – I’m not ready to be pessimistic just yet! If the murres do succeed in hatching some chicks, this year’s median chick hatch date will likely be the latest ever recorded at Yaquina Head.

The complex topography of “Stegosaurus” and the other smaller subcolonies at Yaquina Head may provide sufficient cover from aerial predators for at least a small number of murres to breed successfully.

This year we are also systematically monitoring breeding murres and cormorants at Pirate Cove in the town of Depoe Bay. We’re employing the same protocols as at Yaquina Head, just with slightly less frequent visits. While the situation at these two colonies is broadly similar, we’ve documented fewer eagle disturbances per hour of observation at Pirate Cove than at Yaquina Head so far. Because of this, a small number of murre eggs have now been incubated for at least two weeks and I am hoping that murres at this colony will successfully produce at least a few chicks.

Also of note this year is the consistent Tufted Puffin sightings that we’ve had at Yaquina Head! As many as three individuals have been observed at once, and we’ve seen the birds circle the murre colony numerous times over the course of some mornings. One Tufted Puffin even landed on the backside of Colony Rock, where puffins once bred. While there haven’t been any signs of a nesting attempt, our hopes are high for continued puffin activity throughout this season and next.

If you’re around at Yaquina Head in the mornings, come introduce yourself! I’m typically joined by a great team comprised of Jacque (REU intern), Neci (Doris Duke scholar), and Ricardo (Environment for the Americas BLM/YHONA intern) and we’d be happy to say hello.