Changes in breeding-bird populations on a 210-acre farm area were observed from 1947 to 1952. During this period, clearing, drainage, and planting changed the area from a partially abandoned farm with only 34 acres in cultivation to a modem conservation farm. Number of bird species nesting in the area was about 10 per cent lower in the last three years than in the first three years; number of nesting pairs declined about 40 per cent. The greatest decline was in species characteristic of brushy habitat; these were the most abundant birds on the area at the start of the study. For these species, approximately eight acres of planted hedges and field borders did not serve as an adequate substitute for 63 acres of brushy fields. Other birds were so limited in number during the breeding season that it is unsafe to conclude what effect agricultural practices had on their populations.