Lost in the Grass?
By Joshua Brown Article published May 23, 2007
This is supposed to be a trip in search of small songbirds that nest down low in the grass: savannah sparrows — streaky brown birds with a yellowish eyebrow stripe — and bobolinks — black birds that look like they’re wearing a tuxedo backward and sound like the emphatic beeping of R2D2.
Instead, in a wet hayfield behind Jim Maille’s dairy farm on Dorset Street, in the strange blue-and-pink gloom of the pre-dawn, ornithologist Allan Strong peers at the sky, watching a tiny cloud of black specks rocketing north.
Did you see that?” he says to his post-doctoral student, Noah Perlut.
“What?” says Perlut.
“Brant,” he says.
To one untrained reporter’s eye, they’re barely discernable as birds. The more skilled might guess they’re some form of waterfowl. But Strong’s years of careful looking allow him to home in on the subtle shapes of fast-flying feathers — and know that these specks are brant, a coastal goose rarely seen in Vermont.
You might say he’s got the right search images in his mind when he looks for birds. Unfortunately, the grassland birds he’s been studying in these fields — the savannah sparrows and bobolinks — have the wrong search images in theirs when they look for nest sites.
A nest of troubles
At least they’re the wrong images now, in an era of intensive hayfield management. “These early-hayed fields are really attractive to these birds,” says Strong, an assistant professor in the Rubenstein School of Environment and Natural Resources, sweeping his hand across the shrub-free, rich green grass. “But they’re future death traps.”
When these sparrows and bobolinks look for a good place to nest, their search is probably based on landscape cues carried from thousands of years in their history, when they lived on the prairie. But now, when they settle down in Vermont grasslands during April and May, they stand little chance of successfully raising young. Strong’s research across the Champlain Valley, funded for the past six years by the U.S. Department of Agriculture, makes it clear that nearly all their nests and nestlings will be wiped out by passing tractors and mowing blades before the young can fly. And with three harvests as the norm, the mowers will be back again too soon to allow adult birds to successfully re-nest.
“These birds are part of Vermont’s agricultural heritage,” Strong says quietly, as he untangles a male savannah sparrow from one of twelve nearly invisible mist nets he and Perlut and a group other researchers from UVM and Plattsburgh State have festooned across the field. “The reason these birds are here is because we have a dairy industry.”
But since the 1960s dairy farmers have moved toward earlier and more frequent hay harvests because protein levels in grass are higher in the early season. Along with development of former farmland and reversion of fields to forest, this change in hay cutting is one major reason why Northeastern grassland songbird populations have been in steep decline. Some, like Henslow’s sparrow, are in a freefall toward extinction. It’s a painful irony that several centuries of agriculture allowed these birds to become established from New York to Maine and several decades of agriculture may be a primary cause of their demise.
But there is reason to hope, Strong thinks, that some changes could slow and reverse the dwindling numbers of these birds.
“In May and early June the birds are really vulnerable, but if we delay the cutting beyond that, many birds can survive. We have very good nesting success for both of these species with cuts that range from late June to mid-July,” he says, even though some conservation guidelines suggest that waiting until August is necessary.
While dairy farmers have little flexibility to alter their cutting schedules — the early hay is economically critical in the cut-throat world of commodity milk prices — “there are a lot of fields out there that are managed like lawns,” he says. “Some people have what used to be a hay field that’s now a house on 20 acres: they keep it clear because they like it. These are the landowners we’re really thinking of as our primary target” for implementing later hay cutting, he says.
And if some farmers were to make a first cut in late May and then wait 65 days, the delay “could provide enough time for both species to successfully fledge young,” Perlut and Strong and their colleagues reported in a December 2006 edition of Ecological Applications.
For farmers focused on the highest protein quality for dairy cows, much adjustment in cutting days is probably not going to happen, he says, but some might be willing to leave a few of their most bird-rich or grass-poor acres alone — especially with financial incentives available from the Vermont office of the Natural Resources Conservation Service, a part of the USDA: farmers who agree to cut before May 31 and let the field rest for 65 days can receive $100 per acre.
“We’re trying to help the landowner, as well as the birds, with this new incentive,” says Toby Alexander ’94, state biologist for NRCS, “but no one has signed up this year.”
“Al and Noah have been very helpful to NRCS in developing this program,” he says. “It’s a hard pill to swallow for some ag folks, though; you’re getting rid of good cuttings. We may need to tweak the program for next year and up the incentive.”
Go to the people
In any case, Strong would like to travel around the state talking with farmers and other landowners. “We’ve got most of the basic biology licked. And we have a pretty good sense of what the birds need to keep viable populations,” he says. “Now it’s time to go to the people and talk about management.”
But there are still many unanswered science questions, like what are the evolutionary consequences of modern hay management (since the pairing behavior of the birds changes in response to a field being cut)? And where exactly do the adult bobolinks go when they abandon a mowed field?
The roughly 3500 birds Allan Strong and Noah Perlut, and a large cadre of other researchers and students, have caught and banded on both sides of Lake Champlain over the years will help provide answers. “But it's our responsibility to get the word out about these birds, not just do the science,” says Perlut, as he gingerly turns over a quivering sparrow to look at four tiny plastic and metal rings, two clipped around each leg.
“Band 1881121156,” he says to Nate Zalik MS ’07, who writes the numbers in a field notebook, “bill length, 8.8, width, 4.06.” Then he looks up toward the rising sun. “Such cool little critters,” he says, and lets the bird go, dipping and darting across the glowing grass.