Plants and Breeding Bird Response on a Managed Conservation Reserve Program Grassland in Maryland

Abstract

Currently over 14.6 million ha of land at an annual cost of US$1.76 billion are enrolled in the Conservation Reserve Program (CRP). The habitat benefits of CRP frequently are lauded, but documentation that wildlife is responding as hoped is urgently needed. We evaluated plant and breeding bird responses to 92.4 ha of CRP grasslands at Chino Farms in northeastern Maryland, USA. In 1999 we seeded 12 contiguous CRP fields with 5 mixtures of warm-season grasses representing various growth-form heights in a replicated experimental design, and used mowing and topical herbicide applications to control noxious weeds and facilitate stand establishment. In 6 years cumulative plant species richness increased to 261, 105 of which were species exotic to the region. During the third growing season, we initiated a schedule of prescribed burning on a 3-year rotation to remove accumulated litter and to retard woody succession, and in 2003 we added additional management to control aggressive plant species. Several at-risk bird species colonized the restored grasslands in the first year and established sustainable breeding populations. We implemented a comprehensive observation and banding program, which included mapping male territories for selected bird species and recording nest locations. We marked 1,985 grasshopper sparrows (Ammodramus savannarum; GRSPs) in 7 years. Breeding GRSP populations ranged annually from 70 to 90 socially monogamous pairs with an additional 40 non-territorial males. Annual return rates in the last 5 years were 57% for adult males, 41% for adult females, and 12% for hatch-year individuals. Adults and young birds exhibited high site fidelity, but overgrown fields left unburned for 2–3 years were unpopulated by GRSPs but attracted several shrub-land bird species. Habitat preference for territories was influenced more by vegetation structure than by plant species composition. We recommend the management of grasslands restored for birds include spatial and temporal rotation of prescribed fire and herbicide applications to sustain vegetation physical structure rather than species composition.