Oil Fields: Predators’ Boon, Birds’ Bane

Oil field development along Alaska’s Arctic coast, though widely reviled by environmentalists, has been unexpectedly beneficial for predators such as foxes and ravens. The news isn’t so good though, for some of the migratory bird species on whose eggs and chicks those predators feast.

“Nest predation near oil field infrastructure may be a contributing factor in declines of migratory bird species,” says Joe Liebezeit, a biologist with the Wildlife Conservation Society and lead author of a September study in the journal Ecological Applications looking at the predator and bird populations around oil fields in Alaska. Roughly 85 species of shorebirds, songbirds and waterfowl breed on the Arctic Coastal Plain each summer, and more than one-third of those species are birds of conservation concern, according to 2008 U.S. Fish and Wildlife Service statistics. Foxes, gulls, ravens and other nest predators are drawn to the area by artificial food sources — like Dumpsters and landfills — as well as by buildings, bridges and culverts that serve as den and perch sites on the flat, windswept tundra.

The research team monitored nearly two thousand nests over four seasons at seven sites. The sites closest to manmade infrastructure, Prudhoe Bay and Kuparuk, were within a mile of oil field development, while the furthest sites were up to fifty miles away. The team identified nests by dragging a rope over the tundra to flush the birds from their hiding places. They also counted the predators in the vicinity of the study sites. They found that predator numbers increased within about three miles of human development, while songbirds such as the Lapland Longspur, which migrates from the southern U.S. to the Arctic to mate, struggled to keep their offspring alive. Because longspur chicks remain in the ground nest, susceptible to predation for nearly two weeks after hatching — a long time for birds nesting in the open — researchers believe they’re more vulnerable to predation.

Though scientists think loss of habitat at wintering and stop-over areas around the globe is a major factor in declines of migratory bird populations in recent decades, nest predation at breeding grounds may contribute to declines of some species as well. Studies like this one, which focused on regional relationships between migrating birds and the ecosystems they visit, are important for the preservation of globetrotting species, according to U.S. Fish and Wildlife biologist Richard Lanctot, who was not involved with the paper: they can show where to concentrate efforts “to get the most conservation bang for the buck.”