Eastern Towhee, Field Sparrow, Song Sparrow, Indigo Bunting — most people have never heard of these bird species. But if you took the time to search any overgrown pasture, you would find them. Unfortunately, these birds, as well as nearly three-fourth of New York state’s other shrubland bird species, are on the decline.
This past summer, a group of Ithaca College students and I conducted research to determine the habitat preferences of shrub-land birds — birds that inhabit grassy areas dominated by shrubs — in New York state. All of the field work was conducted in Sterling Forest State Park, about 45 minutes north of New York City. Within our defined shrublands, we recorded the number of species we observed using spot mapping, a method that utilizes maps to mark the location of birds within a plot. At each survey site, we also determined whether the shrubland habitat consisted of low, medium or high-density shrubs. Low included short herbs and grasses; medium comprised herbs and taller shrubs, like honeysuckle; and high contained very thick, impenetrable walls of shrubs a few meters high. Utilizing the same methods, data on shrubland bird distribution was also collected from an overgrown pasture in Montezuma National Wildlife Refuge and from a power line cut in the wooded area behind the college. Similarly, these regions had defined low-medium-and high-density shrublands. A final set of comparable data was collected from 328 locations across much of New England using a different form of surveying, known as point counts. Using this method, the surveyor stands in one location and counts all the birds heard or seen within a 200-meter radius.
After the data was compiled for each site, we discovered that shrubland birds as a whole tended to avoid highly dense shrub areas. Instead, we found a slight preference toward medium-density shrub growth.
However, we did find that individual species had specific habitat preferences that differed from other shrubland birds. Across all sites, Field Sparrows were most commonly found in low-density shrubs, consisting mostly of low herbs and grasses. Indigo Buntings and Blue-Winged Warblers were found in low-density shrubs as well, but they also had a strong preference toward medium-density shrubs. The Eastern Towhee favored medium-high – density shrubs.
So, what does all this mean? For the most part, each shrubland bird species requires a particular habitat that varies from that of neighboring species. As a land manager, it would be counterproductive to create a monocultural habitat with the same shrub density. In order to benefit from the greatest number of shrubland birds in New York, land managers should consider mosaic landscapes that incorporate habitat densities. This can be accomplished through selective cutting and is already underway in some locations in the state. A management plan like this is the best way to ensure the future success of our state’s declining shrubland bird species.
The shrubland bird species are of great importance to the balance of such successional communities. These melodious birds add an element of wonder to the landscapes they call home, and many of these birds possess the vibrant colors that draw the attention of many nature lovers. Students can help out all birds through bird feeders, bird houses and bird-friendly habitats. Helping to maintain a mosaic of shrub growth beneath the power line cuts on South Hill is a great way to preserve the type of habitat that is most desired by shrubland birds.
Stefan Karkuff is a senior biology major. E-mail him at skarkuf1@ithaca.
