|fwg is a long-term project of the ottawa field-naturalists' club|
OLD FIELD HABITAT USUALLY MEANS abandoned agricultural land in the early stages of succession when grasses and wildflowers dominate. Left alone, the land will slowly revert to climax forest.
Spring 1991: At that time this area was still being used for agriculture.
Fall 2007: Just before cutting.
Fall 2007: Agriculture and Agri-Food Canada used heavy-duty equipment to cut herbaceous and woody species. Shrubs and small trees had to be removed by hand in advance.
Fall 2007: Just after cutting.
Abandoned agricultural fields as wildlife habitat
The first plants to colonize fallow land are usually alien (non-native) species, such as burdock, thistle, amaranth, shepherd's purse, Queen Anne's lace, and the various introduced grasses. Termed pioneer species because they are first on the scene, these aggressive sun-lovers find the open, cleared land perfect for quick growth. By year 2, native species begin to appear and will eventually displace many, but not all, of the alien invaders. Goldenrods and asters are the most common native plants to emerge early in old field sites, although adjacent vegetation will determine which species appear.
As former agricultural land, old fields have not been viewed as natural habitat, and their value has been overlooked. Fortunately, many biologists now recognize them as valuable wildlife habitat. At the FWG, we have set aside a small area to show visitors what old field habitat looks like. To keep it from evolving into woodland, as it would naturally, some management is required. The easiest way to maintain old field habitat is to mow the area, although burning and grazing by livestock are two other management techniques. The timing of the cut-back depends on the rate of emergence and growth of woody species, but every 57 years should be about right for our site.
Wildlife use of old fields depends on the size of the field, the surrounding habitat, and the availability of food, cover, and nesting sites. The old field at the FWG is bordered on the west by an extensive thicket of crabapples, buckthorn, and other shrubs. Along the east, north and south boundaries are scattered trees, both deciduous and coniferous, open grassy patches, and more small thickets.
In the country, old fields are often quite large and, if edged with thickets and woodlots, can attract a wide variety of wildlife. Raptors such as red-tailed hawks like to nest in tall trees next to open fields where hunting is easy; short-eared owls prefer old field sites for nesting and for winter roosts. Northern shrikes make extensive use of old field habitat if there are sufficient tall shrubs or trees nearby for perching. One year a northern shrike spent a few days during migration in our old field site.
Although the FWG site is not large enough to attract ground-nesting birds to stay and breed, we have found meadowlarks, savannah sparrows, and bobolinks using the site briefly during spring migration.
Old field ecosystems are also used by small rodents, groundhogs, and foxes. Wood frogs are occasionally observed in our old field, and a variety of insects keep the site humming with life all summer long. Black swallowtails, red admirals, spring and summer azures, silvery blues and monarchs are only some of the butterflies we've seen using the field. Milkweed bugs and milkweed beetles, leafhoppers, soldier beetles, hundreds of bees, grasshoppers, crickets, crab spiders, and daddy long-legs are but a few of the many insects and spiders that can be found there.
Old field habitats are beautiful and fascinating places revealing a world of wonder to the observant visitor. Summer or winter, there is always something to see as the seasons bring changes, each offering a new perspective.