Shifting from spring wheat to winter wheat: a potential conservation strategy for grassland songbirds in cultivated landscapes?

Understanding factors that influence the demography of grassland species in agricultural landscapes is essential given the amount of land under agricultural production. Winter wheat is promoted by avian conservation organizations in North America because it provides cover early in the breeding season without much disturbance to nesting waterfowl. We conducted point-count surveys in fields of winter wheat, spring wheat, summerfallow, planted grassland and native grassland to determine: 1) the relative benefits of winter wheat to songbirds, 2) the extent to which cropland suitability changes over the breeding season, and 3) the extent to which the surrounding landscape influences songbird abundance. Horned lark (Eremophila alpestris), Savannah sparrow (Passerculus sandwichensis) and vesper sparrow (Pooecetes gramineus) were most commonly recorded in wheat and summerfallow fields, and their abundance varied over the breeding season and with the amount of native grassland in the surrounding landscape. Horned lark was more abundant in winter wheat early in the breeding season and its abundance increased with the amount of native grassland in the surrounding landscape. Savannah sparrow abundance increased in all field-types over the breeding season and decreased in cropland fields as the amount of native grassland in the surrounding landscape increased. Programs that encourage or incentivize winter wheat seeding in grassland-dominated landscapes will yield the greatest benefits for horned lark whereas Savannah sparrows would derive the greatest benefit in cropland-dominated landscapes. However, such programs must target cultivated fields to ensure that grassland obligate species are not compromised.