Management of Agricultural Landscapes for the Conservation of Neotropical Migratory Birds
Recent Changes in Agricultural Habitats and Landscape Structure
Cropland Habitats
Small grains. Wheat and other small grains are grown mostly in the Northern Plains. Wheat area increased in the 1970's and has remained relatively stable since then (fig. 2). The area planted to oats has declined by two thirds over the past three decades.
Figure 2. Recent changes in planted area of selected crops and harvested area of hay in the Midwest (USDA 1962, 1967, 1972, 1975, 1977, 1982b, 1987, 1991).
Corn and soybeans. The area planted to corn in the Midwest declined in the 1960's, increased in the 1970's, then declined in the late 1980's (fig. 2). Soybean area increased steadily from the 1960's until the 1980's, then remained fairly stable. Corn and soybean area in Illinois reflected this pattern and increased from 4.9 million ha in 1945 to 8.4 million ha in the 1980's (Warner 1992). Corn and soybeans are usually grown in alternate-year rotation.
Sunflowers. Sunflowers are grown mostly in North Dakota, South Dakota, and Minnesota (USDA 1993). Sunflowers are a relatively new crop in these states (fig. 2). The rapid increase in sunflower area was followed by a decline associated with increased worldwide production (McCormick et al. 1992).
Hayland. After a decline in the late 1960's, the area of harvested hay in the Midwest has remained stable (fig. 2). Traditionally, livestock provided agricultural diversity for farmers who also raised crops, and hay was harvested from untilled prairie which was sometimes seeded with grasses. On tilled land, alfalfa is the primary hay crop. Herkert et al. (this volume) discuss hayland further.
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