On February 8, Noah Perlut, a doctoral student at UVM, gave a fascinating presentation of his research on grassland birds in the Champlain Valley. Twenty-nine people enjoyed his talk at the Dorothy Alling Memorial Library in Williston.
Noah pointed out that grassland bird populations are in sharp decline in Vermont. Of the nine bird species on Vermont’s endangered and threatened lists, four are grassland nesters: Henslow’s Sparrow, Upland Sandpiper, Sedge Wren, and Grasshopper Sparrow. He noted that loss of grassland habitat due to farm abandonment and reforestation is one reason for the decline, but changes in grassland management practices over the past 40 years, particularly earlier and more frequent hay harvests, are also significant.
Noah’s research focuses on Savannah Sparrow and Bobolink nesting success in hay fields and pastures in the Champlain Valley where 25-40% of hayfields have been cut by mid-June. If birds are nesting when the fields are cut, all nests, eggs, and fledglings are destroyed, either by the machinery, or by Ring-billed Gull predation that follows. He noted that Savannah Sparrows, which winter in southern US and Mexico, arrive earlier and can sustain two or more broods per year. Bobolinks winter in southern South America, arrive later and usually breed just once per season. Both species are experiencing declining populations in this area, but the decline is considerably steeper in Bobolinks than in Savannah Sparrows.
He set up an experiment where selected fields were mowed early (by early June), mid-season (late June - early July), or late (after August 1, as all nesting is finished by then). He found that nest success and birth rates were very low for both species in the early mowed fields, and considerably better for both in the middle and late mowed fields. Overall, the early mowing practice was worse for Bobolinks, as he found that following nest destruction, Savannah Sparrows immediately rebred and renested in the same field, and Bobolinks did not, at least not in the same place.
Noah concluded that management practices can be modified to improve breeding success. If a farmer wants to mow early, the first cutting should be in May, and the second delayed at least 65 days. This will allow undisturbed nesting in the critical early June period. For farmers who mow mid-season, a first cutting in late June - early July is optimal, and farmers who mow late present no problem for the birds.
When asked how farmers can be motivated to alter their haying practices, Noah gave the following suggestions. His proposed program is flexible, so different alternatives are available to farmers. He cited a federal program called WHIP (Wildlife Habitat Incentive Program), administered by the National Resources Conservation Service, which provides a financial incentive to farmers to manage their fields in a way that is advantageous to birds. He noted that farmers surveyed had an average of 40 acres of what they considered “wasteland” hay. He would encourage them to let these fields grow, at least until late summer. He would also educate large lot landowners and gentlemen farmers who mow, but do not use the hay, to delay mowing until after the breeding season.
