Category: Predators

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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).
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Linking Rivers to the Sea(birds): Initial Surveys of River Otter Predation on Leach’s Storm-Petrels

By Eleanor Gnam, Seasonal Field Technician

The southern Oregon coast, between Port Orford to the north and Brookings to the south, hosts the largest colonies of Leach’s Storm-Petrels (Hydrobates leucorhous) in the lower-48. Goat Island, half a mile offshore from Harris Beach State Park, is estimated to host more than 100,000 of these small, dusky-colored seabirds. But looking at the island from the shore, you might never know that they’re there.

Leach’s Storm-Petrels

One of Goat Island’s many Leach’s Storm-Petrels.

Leach’s Storm-Petrels, which top out at just under 50 grams at the heaviest, return to their colonies only at night, and nest in underground burrows hidden beneath mats of long grass. Beachgoers who are in the know might be made aware of the colony from the distinctive, musky odor that petrels are famous for—which is strong enough to waft ashore—but otherwise, the colony is practically invisible from more than a few inches above the ground.

LHSPs feed on zooplankton and other planktonic creatures far out to sea, and only return to their colonies under the cover of darkness. During the breeding season, members of breeding pairs will take turns incubating their single egg or chick in the burrow, sometimes remaining underground for four or five days, while the other member of the pair forages. This cryptic, nocturnal behavior likely provides protection against diurnal avian predators. Southern Oregon’s LHSP colonies are close enough to shore, however, that nocturnal mammalian predators can pose a threat.

Project Goals

In collaboration with the U.S Fish and Wildlife Service, Luke Stuntz (MSc student, Seabird Oceanography Lab) and I (Eleanor Gnam, seasonal field tech) are investigating the impact of mammalian predators (mainly North American River Otters Lontra canadensis) on southern Oregon’s Leach’s Storm-Petrels.

We’re seeking to understand how, where, when, and to what extent these predators use petrels as a food source—knowledge that will help inform potential predator management in the future. River otters tend to operate either in loose social groups of unrelated males or in family units of a mother and her cubs. We’re hoping that our research will help us understand the social organizations of the river otters that are using these islands, as well.

A river otter captured via game camera on Goat Island
A river otter captured via game camera on the mainland.

Field Work (May-June)

Luke began fieldwork for this project in May, with trips to our focal islands to survey for predator sign and set up motion-activated game cameras.  Two of the four islands showed definite signs of predator activity (trampling, scat, and prey remains). Cameras on Goat Island quickly revealed activity from multiple social groups of river otters, including a pair of adults and a female with cubs. Because river otters commute between these islands and the mainland, surveys along the coastline are also important for monitoring their activity.

Luke’s initial surveys in May and early June revealed quite a bit of predator activity along the beaches and creeks near these colonies. River otters tend to deposit scat in shared, regularly-used locations called latrines, which aid territory marking and scent-based communication between individuals. They also need to return to freshwater sources frequently, especially after swimming in the ocean, both to drink and to groom their fur. The scat found in the latrines near our focal islands definitely contained digested storm-petrel remains—obvious from the distinct odor.

A game camera deployed over a creek near one of our latrine sites
Luke at one of our latrine sites

On June 15th, we moved into OSU’s Port Orford Field Station to commence full-time fieldwork on the project. Our first step was to revisit the coastline sites near our colony islands and to check out some new sites with the potential to be good river otter habitat. We were surprised by how little fresh river otter activity we found at some of our sites that were very active in May and early June. We’re also seeing them on our game cameras less often than before.

We found evidence of recent activity in several new locations, though, and we continue to see a lot of activity on the beach closest to Goat Island. This raises questions about how frequent and how seasonal these island-going behaviors might be. We’re also starting to wonder about the impact of Route 101 and its associated culverts on river otters’ use of coastal streams. Continuing predator sign surveys throughout the summer, both along the coast and on our colony islands, will help fill in our picture of this predator-prey dynamic and will help us understand how much of a problem it might be for these seabird colonies. We’re planning to expand our predator sign surveys up some of the larger creeks and rivers in the area, as well, using an inflatable sea kayak.

Some river otter tracks, and our tracks, along the beach
Our research kayak (nicknamed the R.V Lontra) ready to go on Hunter Creek