Linking Populations to Habitat

In order to estimate the habitat needed to support our population objectives through time (i.e., habitat objectives), we must link habitat conditions to population response.  Because our population objectives for woodland and forest birds are currently stated in terms of abundance, we must link habitat conditions to density (# individuals per unit area).  Doing so will allow us to scale density to outputs of the HSI models.  For example, density should be lower in marginal habitats than in more optimal conditions.  Because we are using density to set habitat objectives over large regions, small variations in the density estimate can result in large differences in the calculated habitat objective.  The CHJV is actively pursuing several efforts to generate the best density estimates possible.

Cooperative Survey Projects for Forest & Woodland Birds

Forest Bird Assessment Project:  This project focused on estimating densities of six forest interior species.  Partners from five states helped perform point count surveys in highly forested areas and data were analyzed using time-removal and distance models to account for imperfect detectability.

Savanna/Woodland Assessment Project   This project focused on estimating densities of open woodland and interior forest birds in restored sites versus unmanaged sites.  Partners from three states helped perform point count surveys.  Data are currently being analyzed.

HSI Model Assessment Project:   This new project is using data from the previous assessment projects, along with supplemental cooperative surveys in 2009 and other point count data from within the CHBCR as available.  The primary goal of this project is to develop linkages between HSI model estimates and observed densities in order to produce better habitat objectives (i.e. how much habitat is needed to sustain populations at goal).  Further the project will help refine and improve the HSI models for use in site & landscape-scale planning.

Grassland Bird Monitoring Project

Conservation planning requires information on bird distribution and habitat associations.  The CHJV staff is working with cooperators at the University of Tennessee to generate this much-needed information for grassland birds.  This project uses roadside counts and distance sampling to link bird densities to site-scale (e.g., adjacent cover types) & county-level (e.g., acres of grass) measures of habitat composition.  It is supported by the USDA Natural Resources Conservation Service’s Conservation Easement Affects Project and CHJV partner agencies.  The project collected field data from across the CHBCR during 2008-2012.  Results from this project will serve as the basis for grassland bird conservation planning in the CHJV.