Breeding Songbird Use of Native Warm-Season and Non-Native Cool-Season Grass Forage Fields

Converting fields of non-native cool-season grasses to native warm-season grasses has been proposed as a strategy to enhance avian habitat and diversify forage production for livestock, but may yield poor-quality food and cover for birds. We measured territory density and reproductive effort for grassland and shrubland birds in 7 native warm-season grass forage fields (4 hayed and 3 grazed), 7 non-native cool-season grass forage fields (4 hayed and 3 grazed), and 3 native warm-season grass-forb fields managed for wildlife (hereafter, wildlife fields) during May-August 2009 and 2010 in the western Piedmont of North Carolina, USA. Eastern meadowlark (Sturnella magna) territory density was >= 2 times greater in grazed, nonnative cool-season grass fields than other field types, but grasshopper sparrow (Ammodramus savannarum) territory density did not differ among field types. Field sparrow (Spizella pusilla) territory density was >= 3 times greater in wildlife fields than in all other field types. Indigo bunting (Passerina cyanea) territory density was 5.6 and 14.6 times greater in wildlife fields than in grazed and hayed, non-native cool-season fields, respectively. Reproductive effort for grassland and shrubland birds did not differ among field types. Our data suggest dense stands of tall, native warm-season grass are not a better alternative to non-native cool-season grass pastures for grassland songbirds, especially eastern meadowlark. Shrubland songbirds selected wildlife fields managed with less frequent disturbance than forage fields. Moderate grazing to maintain grass heights >= 25 cm may increase quality of non-native cool-season grass and native warm-season grass forage fields for grassland birds. (C) 2017 The Wildlife Society.