Arctic Blog: Tracking the Impact
By Steve Zack, Wildlife Conservation Society
Of Oil Development on Wildlife
19 Jul 2011
As my colleague Steve Kolbe drove us down a gravel road leading away from K-Pad in Alaska’s Prudhoe Bay oilfields, I looked to the side and said, “Whoa, stop!” There, past the multiple pipelines, a common raven was devouring a nest full of eggs, and nearby a glaucous gull waited for leftovers. The nest owners, a pair of white-fronted geese, watched helplessly as this year’s breeding effort came to an end.
I grabbed my camera with its long lens and clicked away. These geese had flown some 2,500 miles from their wintering grounds in central California to breed in this once-remote region. The Arctic summer is short, so there usually isn’t time to try again.
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Predation, particularly nest predation, is a risk for all migratory birds here in the Arctic. The predators, the raven and the gull, are native to the region, and so the predation itself was not unusual. What is telling is that these species, as well as another nest predator, the Arctic fox, have increased in numbers in recent decades with the development of the Prudhoe Bay oilfields. These creatures are, in effect, subsidized predators, as the garbage and the structures associated with Prudhoe Bay — the largest industrial complex in the United States — have drawn predators in greater numbers than in surrounding regions of undeveloped tundra.
All three predator species have access to year-round garbage, and the common raven has nesting sites – buildings and platforms – that otherwise would not exist on the flat coastal plain. Arctic fox wander far less in the oilfields than in territory farther from development. Gulls are always hovering in the hundreds over the immense garbage dump in the middle of the oilfields. Ravens are seen frequently, whereas spotting one in our remote site at Ikpikpuk is a rare event worthy of evening discussion in the communal feeding tent.
In the field this year at both Prudhoe Bay and Ikpikpuk, we are remotely monitoring nests with motion-detecting cameras, in addition to closely monitoring nests on our established study plots. My colleagues and I want to get a clearer picture of the most common nest predators. In addition to the three subsidized species, other predators include three species of jaeger (gull relatives); two owl species; and even ground squirrels and lemmings.
Steve is in charge of nest cameras at Prudhoe Bay this year, installing 15 cameras on shorebird and songbird nests. Aiming the camera just above the nest means that the camera isn’t triggered by the comings and goings of the incubating birds, yet that placement still ensures that intruding predators trigger pictures.
I had spent the morning and afternoon with Steve, checking on the cameras and changing the batteries and memory cards — the sort of rouine work that underlies any successful field experiment. When we found that a nest had been predated, we moved the camera to another one. Although nest success for Arctic birds is high compared to nesting birds in the Lower 48, we have still recorded 12 predation events to date this year in Prudhoe Bay. The cameras also have snapped pictures of Arctic and red fox depredating nests, as well as a songbird nest lost to a raven. We have had a first this year: a snowy owl preying on a Lapland longspur nest. Most predation is recorded by our cameras at “night” (between midnight and early morning) in this season of 24-hour sunlight.
With nest cameras monitoring at both our oil field and our remote site, we are trying to understand how important the “subsidized” nest predators are, and so get a feel for how development indirectly affects the nesting birds in the Arctic. Those data, and that understanding, come slowly but surely as we slog day by day across the tundra checking cameras and nests.
The direct effects of the Prudhoe Bay oilfields are clear. The myriad roads, pipelines, and “pads” (the raised gravel beds supporting the buildings and drilling structures) have displaced the birds that once nested in those places. Some indirect effects, like the abundant dust from the roads, have been shown to affect tundra vegetation and to keep nesting birds away from dust-covered tundra. Yet the most important issues concerning population-level effects have proven challenging to document and clarify.
Take the impact of oil development on caribou. While caribou are numerous and conspicuous throughout the oilfields this time of year (as is again true this year), competing studies and analyses have offered alternative interpretations of the effects on caribou. It seems clear that the oilfields displace caribou (not absolutely, yet measurably) and that calving females are more energetically stressed in the oilfields. Yet other studies have emphasized the capacity of caribou to habituate to the oilfields. This is a politically volatile issue in need of more clarity.
The Wildlife Conservation Society (WCS) recently helped lead an effort to assess the impact of ravens, gulls, and Arctic fox on tundra nesting birds in sites in, near, and distant from the oilfields. Collaborating with industry, federal, and other scientists at sites across the North Slope, we collectively monitored nests of birds for four years. The results seemed as much a black hole as a thorough examination. In brief, we created a model of nest survival and predation from our data set of more than 1,800 nests and asked, statistically, if proximity to oilfield structures had a measurable effect. It did overall for songbirds (mainly the abundant Lapland longspur), as nests within 3 miles of structures faired poorly compared to nests more distant from structures. For shorebirds, we could find no such overall effect.
Thus, our 2009 published paper, with my WCS colleague Joe Liebezeit as lead author, offered a nuanced set of results on the overall role of the indirect effect of oil development as viewed through subsidized predators preying on tundra nesting birds. We had some strong signs of harm done to songbirds and phalaropes, yet we could not detect a strong overall and uniform effect on shorebirds, the group with which we are most concerned.
Still, our work with predators continues. Last month, our other field assistant, Elizabeth Ames, met up with her new colleague, “Friendly Fox,” an Arctic fox unafraid and even friendly with her as she slogs out to our plots in his home range. We frequently see Friendly Fox and his kin showing up on our nest cameras, consuming the eggs of our far-flung migratory birds. Predators and their prey are part of our daily field lives here in the oilfields. Our concern is that as energy development expands into the more diverse, abundant, and productive bird nesting rounds to the west, in Arctic Alaska, that Friendly Fox, ravens, and gulls will follow and consume ever-larger numbers of tundra nesting birds.
12 July 2011: Unraveling the Mysteries of Migration
26 July 2011: A Place for Wildlife in the National Petroleum Reserve
2 August 2011: As Climate Warms, a Shifting Landscape for Wildlife
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