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 6th! 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

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 23rd and we’re hopeful that there will soon be many more!  As for Brandt’s Cormorants, we recorded our first chick back on June 16th 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.

A Bald Eagle seizes an adult Common Murre at Pirate Cove.  This disturbance caused the rest of the colony to flee, leaving the eggs vulnerable to predation by Western Gulls (note the gull with its mouth full, just to the right of the eagle).

Yaquina Head Seabird Monitoring: July 2022 Update

By Yaya Callahan, NSF REU INTERN

Hello everyone!

The Seabird Oceanography Lab is almost midway through the field season here at Yaquina Head Outstanding Natural Area. The murres have not been able to incubate eggs this year and we are expecting a year of no reproductive success. We are continuing our monitoring effort and are anticipating starting diet photography efforts soon at the small colony located in Depoe Bay. 

When observation began in late May at Yaquina Head, we saw the murres repeatedly flushed from the main nesting site Colony Rock by eagles. Often two sub adult and two adult eagles would also flush Lion’s Head, Seal, and Stegosaurus Rock, and the murres would not return to these areas as quickly. By June, later then we expected, murres began to settle and we spotted birds with eggs on Colony Rock. Although the majority of Colony Rock was covered with birds, two locations at the eastern side closest to eagle’s roost remained unoccupied. 

About a week later the avian predator disturbances spiked again. The first one that led to considerable undoing of nesting progress was on June 13th, when three separate groups of turkey vultures flushed murres from the colony. Only one of these groups of vultures was accompanied by bald eagles. These disturbances allowed western gulls to opportunistically take over 30 murre eggs – even dropping some on the ground around the lighthouse. The gull flock continued to grow as on the 17th, we estimated over 50 gulls flying overhead. From then on – apart from the chaotic observation day on June 22nd — it only took one disturbance each observation period for the murres to be completely cleared off. Each time their numbers on colony rock dwindled. When they were present on the rock many were standing and not in their nesting position.

In early July we typically have murre chicks, but this year Colony Rock has been devoid of adult murres and eggs for over a week now. Murres are continuing to raft in the water nearby the colony. There have been some murres attending Stegosaurus Rock and South Headland however they aren’t nesting. Normally, eagle disturbances decline through June, but this year they have been continuing. Additionally, winter conditions persisted through May and upwelling was delayed until June. This likely contributed to the inability of the murres to settle and incubate eggs. Upwelling brings cold nutrient-rich water to the surface that fuels primary productivity and the forage fish murres depend on. Upwelling typically initiates in mid-April prior to when murres lay their eggs. 

A subadult bald eagle attacking a murre adult on Colony Rock.
Photo: Sofia Franco Cruz

Unfortunately, the number of nesting Brandt’s and Pelagic cormorants are low this year. Eagles do not disturb them like they do the murres though many gulls roost on Flat Rock where the Brandt’s are nesting. Flat Rock has quite the dynamic rise and fall in nests; On July 6th we had spotted 35 nests. On June 29th we realized that almost half of these had been abandoned – mostly on the Western and top half of the rock. We are currently following 17 active Brandt’s nests. Additionally, we have two Pelagic cormorant nests on Stegosaurus Rock and we are following 15 Pelagic cormorant nests on South Headland. 

The rocks at Yaquina Head, Oregon.

On the bright side there are three healthy looking chicks on South Headland and we are expecting more on Flat Rock. We’ll make sure to monitor these chicks and keep an eye out for murres though. 

See you again for our next update in August!

Brandt’s cormorants feeding a chick on South Headland (July 8th). Photo: Yaya Callahan