| University of Alaska Fairbanks scientist Stacia Backensto
says Alaska's Prudhoe Bay oil fields offer ravens a near-perfect
human-made habitat. (Courtesy UAF)
Alaska's Oil Field Ravens
INTRO: Alaska's Arctic coast is a treeless, marshy plain in summer and a bitterly cold, windswept wilderness in winter—not exactly the best place for birds that like to nest high above the ground. But toss in a few oil pump stations, communication towers and other structures, and you create a near-perfect artificial habitat for ravens. Doug Schneider has more in this week's Arctic Science Journeys Radio.
STORY: Ravens, those large, raucous, black birds seen perched atop
streetlights or foraging in the back of pickup trucks, were never common on
Alaska's treeless northern coast. But towers, buildings, and landfills in the
state's sprawling Prudhoe Bay oil fields are giving ravens a reason to stay.
Stacia Backensto is a Ph.D. student with the University of Alaska Fairbanks Regional Resilience and Adaptation Program.
She says about 17 breeding pair of ravens have established nests atop communication towers, drilling platforms, pump stations, and other structures within the oil fields.
BACKENSTO: "They are definitely situated for the most part on major facilities
and drill-site pads. They tend to be on the buildings themselves, but there
are some nests that are on communication towers that are next to the
buildings or structures. Some of the nests are on fire escapes. Some of the
nests are on top of exhaust vents. The really smart birds have nests on top
of heated pipes, not too hot, but just warm enough to help a female incubate
eggs during those really cold weeks of early April and May."
Backensto is trying to learn just what impact oil development is having on
Alaska's most familiar bird, and how the area's growing population of ravens
may be affecting the region's other wildlife. She says the oil fields, as well
as nearby Alaska Native villages and abandoned military sites, all provide
ravens along the Arctic coastal plain with the things we all need to survive:
food and shelter.
BACKENSTO: "I think two things happened. We provided a consistent food source
to them at a time when they are usually food-limited in the winter. Given that,
they were able to start being resident birds in those areas. And secondly, the
structures actually gave them an opportunity to nest. That was the primary limiting
factor for a breeding population of ravens on the coastal plain."
During the winter, when natural food is scarce, ravens, sometimes more than 100
at a time, congregate at the Prudhoe Bay landfill. Backensto isn't sure where
they all come from. But with the arrival of summer, Backensto says nearly all
the ravens stop using the landfill and begin to prey on rodents, bird eggs, and
sometimes even the newly hatched chicks of ground-nesting birds.
|A growing population of ravens along Alaska's Arctic coastal plain may be having a negative impact on the region's ground-nesting birds and small mammals. Here, a raven preys on a recently hatched shorebird. (Courtesy Betty Anderson)
BACKENSTO: "We see them focusing to some degree on small mammals, lemmings,
tundra voles. So we find bones and we have actually observed them. What's really
interesting, and I didn't expect to find this, is that ravens kind of walk
along the tundra and poke their heads into the lemming tunnels and eventually
they get one. I call it the random walk. It looks like they are walking randomly
around the tundra and eventually they get something. It's also probably a really
good strategy where there is a high density of nesting birds. They are bound
to flush a bird off the nest by walking along, and they can take the eggs
or the chicks. And we have seen both—birds flying with eggs and birds actually
pick up chicks off the ground."
It's that kind of impact on local wildlife that Backensto hopes to learn more
about as her research on ravens in Alaska's North Slope oil fields heads into
the second of a three-year study.
BACKENSTO: "There's the whole idea that you have an inflated predator population in a particular area around development that would not likely be there without that development."
This summer, Backensto will attach transmitters to a number of ravens to learn
more about their travels along the Arctic coast. She hopes to learn, for example,
where breeding ravens that show up at the landfill during winter, but which
don't have nests in the oil fields, are coming from and where they go once
Audio version and related websites
Thanks to the following individual for help preparing
Regional Resilience and Adaptation Program
Institute of Arctic Biology, UAF
PO Box 757000
Fairbanks, AK 99775-7000
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Regional Resilience and Adaptation Program
Stacia Backensto's North Slope Raven Study
Study Says Ravens Thriving in Alaska Oil Field (Yahoo News)
Ravens' Interaction With Oil Rigs Studied (ENN)