By Lee Anna Sherman
A light wind froths across the headland, kicking up the churn below. Just off Yaquina Head, atop a sea stack named Colony Rock, more than 60,000 seabirds huddle in a wing-towing crush. Audible from shore is a raucous din, the collective cry of nesting females incubating eggs and raising chicks while their mates fly in and out delivering herring and other small, silvery fishes foraged at sea.
“Hey, look at the penguins!” a tourist exclaims, pointing seaward from a viewing deck at Yaquina Lighthouse, Oregon’s tallest. The “penguins” aren’t penguins at all, but common murres (Uria aalge) — roundish, upright birds whose black-and-white plumage makes them easily mistaken for the tuxedoed species of the Southern Hemisphere. Like penguins, murres dive into the inky depths to feed, going as deep as 500 feet. Each summer breeding season for nearly a decade, murre and cormorant colonies at Yaquina Head, Cape Perpetua and other Pacific headlands have been under observation by Oregon State University researchers. From the lighthouse, ornithologist Rob Suryan and his team from OSU’s Hatfield Marine Science Center focus their “digiscopes” (highpowered telescopes with digital cameras attached) on the colony for three to six hours a day, documenting feeding and rearing behaviors — behaviors that can shed light on local ocean conditions as well as larger-scale oceanographic trends.
“Seabirds are a perfect study organism for learning how animals interact in a marine environment,” says Suryan, who leads OSU’s Seabird Oceanography Lab. “Unlike fish, which live underwater and out of sight, the life history of birds is visible to scientists. There’s enormous information you can gather from birds about ocean conditions — climate change, prey fields, dead zones, wind-driven upwelling — and how those conditions cascade through the food web.”
On this choppy morning in July, the scientists watch as a dark form slips from the sky on 6-foot wings. As its shadow passes over the colony, panicked murres plunge by the hundreds from the 50-foot rock, awkwardly flapping their flipper-like wings to slow their descent into the surf. Not all escape. The raptor — one of several bald eagles that have been harrowing the colony daily — skims low, silent as a drone, over those still sitting on their nests. Then, with a swift back-sweep of its yellow talons, the eagle locks onto a murre and retreats while ravens, vultures and gulls raid the unprotected eggs.
“Look how bare it is on the north side of the rock,” says Suryan. “That’s because of bald eagle disturbances. You can see turkey vultures and other scavengers wandering around eating eggs. We call them secondary predators.”
By late July thousands of murres, hectored by eagles and even a few brown pelicans, had abandoned their nests. “Unfortunately, this has been one of the least successful breeding seasons for the common murres at Yaquina Head,” Suryan reported in an online update. Still, some of the chicks survived to fledge. As young as 15 days old and not yet able to fly, each baby murre took a harrowing, nighttime leap off the cliff and (with luck) splashed into the dark surf to join its male parent swimming below, loudly beckoning its offspring. Together, adults and juveniles headed out to sea where they will forage until it’s time, once again, to rejoin the colony for another breeding season.
_________________
Oregon State ornithologists are carrying out studies from the Oregon coast to the Willamette Valley, Cascade Range, Columbia Plateau and the Zumwalt Prairie. See Avian Nations in the fall 2014 issue of Terra.