Due to rapid and widespread habitat loss, population declines among songbirds across North America have declined dramatically. Habitat for grassland nesting birds has been steadily disappearing due to suburban and rural development, invasive species encroachment, and natural succession of grasslands into savannahs and woodlands. In our region, a variety of grassland-nesting species have been affected, including bobolinks, eastern meadowlarks, blue grosbeak, dickcissel, grasshopper sparrows, savannah sparrows, vesper sparrows and field sparrows, all of which utilize cultivated fields for nesting.
The Value of Unmowed Hay Fields
In the absence of naturally occurring grasslands, many species of birds take advantage of the protective cover and feeding opportunities available in cultivated farm fields, which have come to represent an important nesting habitat.
Timing the cut of hayfields and meadows for late summer is an easy way to counteract this rapid and widespread habitat loss. Equipment operators are often unaware of the high number of nests that are destroyed when they are mowed. There are a variety of changes that can help to preserve nests in a field. A good rule of thumb is to wait until at least July 15th to mow hay which allows grassland-nesting birds to fledge one to two broods of young. When possible, wait until August 1st to increase survival of fledglings in any late-season broods.
Although the timing of cutting is critical to nesting success, many farmers have limited flexibility in their ability to delay cutting because of declining forage quality after their cool-season grasses peak in nutritional value—usually June or early July. As a long-term solution, replace cool-season grasses with warm-season natives in some of your fields. Native grasses such as switchgrass, big bluestem, little bluestem, and Indiangrass peak in mid-July, are tolerant of mid-summer heat, and provide high quality forage and hay.
Alternatives to Delayed Mowing
For landowners who are unable to delay harvest, consider these methods to reduce your impact on songbird populations:
Mow hayfields from the inside out, and towards any uncut fields. This encourages vulnerable fledglings to scatter through the remaining cover rather than into the open.
Leave a 30-foot border along wooded areas or fence rows. These areas are often less productive for hay and dry slowly, but are valuable to nesting birds and other wildlife, especially the eastern box turtle.
Raise blade height to 8 inches to reduce nest destruction, and provide some residual cover for birds.
Allow for a period of re-growth if a meadow is cut twice a year. Time the first cutting for late spring (before May 15th) and the second cut approximately 65 days later. The regrowth period should correspond with adequate time for nesting and fledging. Please note, with this method, some egg clutches will be lost in the first mowing; however, some birds may return to re-nest.
Our combined efforts can help reduce the population declines which began nearly fifty years ago as grasslands and farm fields were lost to suburban sprawl. By delaying their haying, landowners can lead their communities in protecting these sensitive species and restoring ecological balance to the region.
