Gambling With Gulls, Beleaguered Bogs, and Other Stories

All around Cook Inlet, young shorebirds are strengthening their wings. They’re the survivors, the chicks who made it to fledging. As they prepare for the next big challenge—their first migration—here’s a sneak peek at the months that got them to this point.

Big news for this year: unusually high chick survival in Hudsonian Godwits. At their long-term study site in Beluga, researchers from UMass Amherst put tiny radio tags on newly hatched chicks, then tracked their movements using 115 radio receivers spread across the study site. Thirty-four godwit chicks were tagged; of these, six survived their first three weeks and went on to fledge. This ~18% chick survival rate may not sound like much, but compared to the ~5% seen in previous years, it counts as a serious win for the birds. 

“It's amazing to see so many godwit chicks flying in the bog,” says PhD researcher Feipeng Huang.

The relatively high chick survival rate is probably due to lower-than-usual predation pressure from short-billed gulls. In Beluga, godwits often choose to nest near the local gull colonies. This tactic is a double-edged sword. On the one hand, there’s nothing like a swarm of furious gulls to drive off aerial and terrestrial predators. During the nest incubation phase, neighboring godwits get to piggyback on that built-in defense system. But the two species tend to hatch around the same time—and at that point, fragile young godwit chicks become a target. Not as a menu item, in this case. Short-billed Gulls (and other colonial seabirds) are simply overzealous in defense of their own chicks; if they can pull the deed off, they’ll kill any creature that comes too close.

This year, though, the gull nests hatched later than usual—and later than the godwits. By the time hostile gull parents came knocking, the godwit chicks were already large enough to be much less vulnerable. “That gave them a huge boost,” says Huang.

Nothing is ever straightforward in ecology, however. Other shorebird species nesting right in the same bogs experienced the breeding season quite differently. “This year, we were also tracking Short-billed Dowitchers and Lesser Yellowlegs. They did not do as well as the godwits,” says Huang.

Same bogs, same year, similar species … why would these birds fare differently? That’s where data analysis comes in. The raw data shows what happened. Huang’s job now is to sort out the underlying connections that explain why things might have happened that way. Links between different factors—factors like predation, insect availability, chick size and weight, water levels—will show what influences the breeding success of Cook Inlet’s various shorebird species.

On the other side of the inlet, project collaborators from the Alaska Department of Fish & Game are assembling another dataset to help. This season, they repeated a series of bird surveys originally made in Anchorage’s bogs during the 1990s. Details like each bird’s location, behavior, and use of the habitat, combined with data on vegetation and wetness, reveal the relationship between shorebirds and the bogs themselves.

The original 1990s surveys act as a frame of reference. With this year’s surveys in hand, the team can assess how things have changed for bog-dwelling shorebirds over the past three decades. Perhaps most importantly, these insights help forecast how local birds will be affected by future changes to Cook Inlet’s bogs.

Because, of course, things change over time. At some of the original survey locations, the brush is now so overgrown that access is impractical, and visibility for bird-spotting nonexistent. And 30 years of development has wrought substantial change, with trails and parking lots built, suburbs extended, wetlands drained. “There was one survey point where the point itself was no longer in a bog, it was in someone's living room,” says wildlife biologist Arin Underwood, who led this year’s surveys. Some of that bog still exists—and the living room’s owner gave Underwood permission to survey from his backyard—but these days it harbors few shorebirds.

Preserving wetland habitat can be a hard sell. “Bogs get kind of a bad rap sometimes,” says Underwood, noting the perception of “‘a nasty bog that’s filled with mosquitoes and mud and nothing else’” can make swampy habitat a no-regrets candidate for development. She wishes everyone had a more complete understanding of what a bog actually has to offer—roses, cinquefoil, berry bushes, wood frogs, swans, loons, shorebird nests, calving moose mothers, and all.

Take Turnagain Bog, next to Ted Stevens Anchorage International Airport. For more than half a century, it’s been a relictual scrap of what was once a much larger wetland area. Yet it is far more than just a leftover chunk kept as a handy buffer between airstrips and nearby residential neighborhoods. Even now, Lesser Yellowlegs, Greater Yellowlegs, and Wilson’s Snipe still nest there. “It’s encased by a fence and surrounded on all sides by massive development,” says Underwood. “But it's just so beautiful in there. It’s like this snow globe of a little ecosystem still trucking along.”

Cook Inlet’s beautiful buggy bogs have done their best for the birds this season. Now, the region’s shorebirds are gathering, readying for southward migration to their wintering grounds. Researchers like Underwood and Huang will migrate, too—indoors, to sit behind a computer. There’s a mountain of data to analyze, and an underlying ecological framework just waiting to be unearthed.

But some things don’t require statistics or computer modeling to understand. Huang reflects on the famously massive flocks that are typical of shorebird migration, and on each chick’s struggle to make it through the spring and summer to ultimately join such a flock. “Before I worked at the breeding grounds, I did not appreciate that it's just so hard for these birds to make it to that point,” says Huang. “Every single individual that's made it is so precious.”

—Alice McBride is a freelance science writer/academic editor/ecologist from Maine.