Relative importance of local and landscape variables on site occupancy by avian species in a pine forest, urban, and agriculture matrix

Abstract

In the Southeastern USA, planted pine forests are increasingly embedded in a matrix of urban and/or agricultural land. Most avian conservation management in these forests has primarily focused on local (stand) characteristics and less attention has been given to landscape characteristics. We investigated the relative influences of local and landscape variables on site occupancy of 17 avian species in pine forests in urban and agricultural matrices. During May–August 2010 and 2011, we conducted bird surveys and vegetation surveys in stands dominated by loblolly pine (Pinus taeda) in the Sandhills Ecoregion of Georgia, USA. We developed 8 single-season occupancy models. An autocovariate was also incorporated to account for spatial autocorrelation. We used three principal components summarizing environmental characteristics at each of three spatial extents (one local and two landscape scales, 500m-radius circle and 1km-radius circle surrounding a point) as covariates. Of 17 species, occupancy by 5 species was associated with local vegetation variables and by 8 species with variables at 500m and/or 1km landscape scale. Occupancy by forest interior species had a greater association with landscape variables, whereas occupancy by pine–grassland species was related to local variables. Urban development and agricultural land use positively influenced the occupancy of species associated with landscape variables. To improve overall avian diversity, our results suggest that forest management needs to consider both local vegetation characteristics and landscape characteristics, and that the potential habitat value of pine forests in the urban/agricultural matrix should not be ignored.