OREGON STATE UNIVERSITY

Rapidly growing murre colony draws interest of scientists – and predators

07/28/2010

NEWPORT, Ore. – A rapidly growing colony of common murres at Yaquina Head near Newport has drawn the attention of predators – both expected and unexpected – as well as of scientists, who say the bird is an “indicator species” that can provide vital information about climate change.

An estimated 50,000 murres use the conveniently located rocks just offshore from the Yaquina Lighthouse, where viewing platforms offer close-up views for tourists as well as researchers.

Rob Suryan, an Oregon State University seabird ecologist, is leading a multi-year study of the birds that is gathering information on their reproductive success, diet and foraging activities. Murres are deep-diving birds that descend up to 500 feet below the surface to target herring, smelt, anchovies, sand lances and juvenile rockfish – the same diet as many fish species including salmon, halibut and adult rockfish.

Their survival and reproductive success is closely tied to ocean conditions and when biological productivity is good – from plankton, to copepods, to small fish – life is usually good for the murres. But Suryan and his colleagues from OSU, the Bureau of Land Management, and the U.S. Fish and Wildlife Service have found murre survival can be influenced by predators as well as by prey.

Throughout the breeding season, bald eagles would perch on two wind-battered fir trees on the edge of Yaquina Head and then swoop down to grab adult murres. As the other murres scattered, gulls would rush in and scoop up the murre eggs, Suryan said.

“Our field crew also recently observed an immature brown pelican land on Flattop Rock and run through the colony flapping its wings,” Suryan said. “As it zigzagged through the colony, it ate 10 common murre chicks and chased away many of the adults, allowing the gulls to come in and go through their egg-stealing routine.

“Who would have thought that a pelican, of all things, would devour 10 young murres in a matter of seconds?”

Scientists say studies like this are particularly important because murres are an indicator species that may be one of the first seabirds to demonstrate negative impacts of climate change. One of the first visible signs of poor ocean productivity, Suryan noted, is the presence of seabird carcasses on local beaches. And although the central Oregon coast is one of the most monitored ocean regions in the world, upper trophic-level species like seabirds are not often included in long-term monitoring programs.

The seabirds at Yaquina Head, however, are ideally located and the data that Suryan and his colleagues are gathering can easily be coupled with OSU-gathered data on oceanographic conditions, allowing integrated food web studies.

Though the murre population at Yaquina Head may be one of the largest on the West Coast, these colonies can disappear rapidly, said Suryan, who is an assistant professor of fisheries and wildlife at OSU, working out of the university’s Hatfield Marine Science Center in Newport.

In the late 1980s, surveys by the U.S. Fish and Wildlife Service showed there were some 12,000 murres each in colonies at Yaquina Head and several miles north at Gull Rock near Otter Crest. Over the past couple of decades, the Gull Rock colony declined and was eventually abandoned, while the Yaquina Head colony has greatly expanded. Suryan speculates that predation by eagles and egg-robbing gulls may have forced the murres to move from Gull Rock to Yaquina Head.

“Seabirds are usually faithful to nesting sites,” he said, “but if they have consistent failure to produce young, they will move. But we don’t really know if their overall numbers are increasing or decreasing until we get more yearly data and monitor reproductive success.”

Suryan said murres spend most of the year at sea and return to land in early spring to establish a colony. The females typically lay a single egg some time in May or June, and by early August, both adults and young murres will leave the colony and return to sea. Scientists are trying to learn more about what kind of nesting success rate is necessary to maintain the murre population – while factoring in predation rates and availability of forage fishes.

“It’s incredibly complex,” Suryan said, “but these birds can help tell us how a variety of marine life may be responding to ocean conditions as they change.”

As part of the study, students from OSU and other universities – part of the Research Experiences for Undergraduates (REU) program – staff the platforms on Yaquina Head from which they monitor how many birds lay eggs, the rate of predation, and even what kind of fish the adults are feeding their young. That dietary information is then compared with stomach contents of commercially caught salmon, halibut and rockfish from Newport-based boats.

Amanda J. Gladics, a master’s student at OSU in the Marine Resource Management program, said preliminary data suggests an overlap in the diets of the birds and fish.

“We’re working directly with commercial and sport fishermen on the project, who share the stomachs of the fish they catch so we can analyze them,” said Gladics, who is from Beaverton, Ore. “We’ve found a lot of juvenile rockfish in the salmon and adult rockfish stomachs, and they’re being observed as an important part of the murres’ diet, too.

“We don’t have enough data to draw any conclusions yet,” she added, “but we would expect in years when particular prey species are abundant, the forage fish predators that we study would have more similar diets, and the opposite would be true in years of low food abundance.”

This is the fourth year of the OSU-led study, with funding from the Bureau of Land Management and U.S. Fish and Wildlife Service, and additional support from the National Science Foundation through the REU program. It continues the work begun by Julia Parrish from the University of Washington who conducted studies of murres in the area from 1998 to 2002.

“Scientists studying ocean or atmospheric conditions can look at ice cores or sediment cores and reconstruct the past,” Suryan said. “With birds, we can’t do that, so it’s important to establish a longer time series of data that will begin to show us how these birds respond to their environment and to predation.”