Bird Use and Nesting in Conventional, Minimum-Tillage, and Organic Cropland

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We examined seasonal bird use and nesting activity in fallow, sunflower, and wheat fields among conventional farms (using fall and spring tillage and pesticides), minimum-tillage farms (using reduced tillage), and organic farms (using zero synthetic pesticides) in southeast North Dakota. Observers recorded 18 species in crop fields in spring, 70 in summer, 40 in fall, and only 11 in winter. Birds counted in cropland in spring were mainly transient migrants. Spring bird densities were highest in minimum-tillage fallow fields that provided enhanced food and cover. There were no differences in bird densities among crops or field types in fall or winter, but mean densities in summer were highest in fallow fields (14-23/10 ha). Fallow fields also had the greatest mean number of nesting species (1.9/field) and the highest mean nest densities (15 nests/10 ha) probably due to increased amounts of plant litter cover. Compared to conventional fields, the mean number of nesting species (1.6 and 1.9/field) and mean nest densities (10-12 nest/10 ha) were higher in minimum-tillage and organic fields. Overall, hatching success was low for waterfowl (0%) and shorebirds (18%) and nest success was low for passerines (14%). Hatching success for shorebirds and passerines was not different among field types or crops when all loss factors were considered. Nest losses were caused primarily by predation and farming activities. When predation was not considered, hatching success was higher in minimum-tillage fields for passerines and in wheat fields for shorebirds. Although it would be difficult to reduce predation to increase nest success, mortality of nests and young might be lowered by reducing tillage frequency.