Breeding Ecology of Vesper Sparrows in Corn and Soybean Fields

Abstract

The breeding ecology of vesper sparrows (Pooecetes gramineus) was studied along fencerows between corn and soybean fields in central Iowa. Territories included portions of both corn and soybean fields, usually within 80 m of the fencerow. Breeding densities were greater along more shrubby fencerows. Nesting success in corn and soybean fields was low, 9% before 15 June and 28% thereafter. Nest losses resulted primarily from agricultural operations (27 % of all nest losses) and predation (29 % ). Nest predation was higher near agriculturally nonproductive areas. Late in the season, when most of the successful nesting by vesper sparrows occurred, washes were heavily used as nest sites. Nest placement shifted seasonally, probably in response to changes in food availability and cover for nesting activities. Renestings during the middle of the breeding season were farthest from nonproductive areas. Annually, vesper sparrows produced an average of 2.8 young/pair, probably below replacement levels. Vesper sparrow breeding success likely would be greater if the number of tillage operations was reduced and crop residue was retained on the