Bird Nesting in Iowa No-Tillage and Tilled Cropland

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Abstract
Nesting of birds was studied in 355 ha of nontilled (no-tillage) and 129 ha of tilled cropland. No-tillage treatments included corn planted into corn residue, corn planted into sod residue, and soybeans planted into corn residue. A control treatment was corn planted into tilled cropland. Twelve bird species (excluding brown-headed cowbirds [Molothrus ater]), with an average density of 36 nests/100 ha, nested in no-tillage fields; only 3 species, with an average of 4 nests/100 ha, nested in tilled fields. Nests in no-tillage fields were located in crop residue that was shorter but of similar coverage to that in random locations within the fields. Nests in tilled fields were positioned in locations where crop residue was more concentrated but of a height similar to that in random locations. Twenty-two percent of all nests in crop fields were successful, 54% were lost to predators, and < 6% were destroyed by farming implements. Nesting success probably was below levels needed to sustain viable populations without influx from other areas.