Evaluation of unharvested refugia for grassland bird conservation within active hayfields

Abstract

Agricultural grasslands such as hayfields and pastures frequently act as ecological traps for grassland birds because of harvest practices that interfere with successful nesting. Conservation measures that improve reproductive success while allowing farmers to maintain agricultural outputs are needed to help stem widespread grassland bird population declines. We evaluated leaving uncut patches ("refugia") within harvested hayfields to provide cover, reduce field abandonment, and promote renesting by three grassland species: Bobolink (Dolichonyx oryzivorus), Grasshopper Sparrow (Ammodramus savannarum), and Eastern Meadowlark (Sturnella magna). In 2014-2016, we left five refugia (0.25 ha each) within a 23-ha hayfield in New Jersey, USA. We found refugia were used more relative to cut areas by Bobolink and Grasshopper Sparrow, but not by Eastern Meadowlark. The presence of refugia also appears to have reduced field abandonment following harvest in all three years for Bobolink and Grasshopper Sparrow when compared to two adjacent fields that lacked refugia. We observed territorial singing, but no evidence of renesting in refugia following harvest, though this may relate to the relatively late harvest dates (26 Jun-3 Aug). Response patterns were consistent over the three years of the study and suggest that leaving small refugia within active hayfields could be a valuable supplement to current management incentive approaches.

Keywords

• agriculture
• conservation
• experiment
• grassland birds
• hayfield
• mowing
• private lands