Latest Publications

Adams, H.L., L.W. Burger Jr., S. Riffell. 2015. Edge effects on avian diversity and density of native grass conservation buffers. The Open Ornithology Journal 8:1-9. Download

Oedekoven, C. S., S. T. Buckland, M. L. Mackenzie, R. King, K. O. Evans, L. W. Burger. 2014. Bayesian methods for hierarchical distance sampling models. Journal of Agricultural, Biological, and Environmental Statistics 19:219-239. Download

Evans, K. O., L. W. Burger, S. K. Riffell, M. D. Smith, D. J. Twedt, R. R. Wilson, S. Vorisek, C. Rideout. 2014. Avian response to conservation buffers in agricultural landscapes during winter. Wildlife Society Bulletin. Download

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Data Analysis

Analyses of breeding season and fall covey survey data collected as part of the CP-33 Monitoring Program are conducted using a 3-tiered approach. Results are generated program-wide, regionally (within each Bird Conservation Region (BCR)), and within each state. Density estimates are obtained for fall covey data, and for species with adequate numbers of detections in the breeding season using program Distance 6.0.

We use conventional distance sampling (CDS) and multiple covariate distance sampling (MCDS) in program Distance 6.0 to estimate a detection function for each species of interest based on the probability of detecting a singing male or calling covey at a given radial distance (m) from the survey point. Breeding season species of interest for all BCR's/states included northern bobwhite (Colinus virginianus), eastern meadowlark (Sturnella magna), and eastern kingbird (Tyrannus tyrannus). In accordance with species' range some BCR's also include dickcissel (Spiza Americana), field sparrow (Spizella pusilla), grasshopper sparrow (Ammodramus savannarum), vesper sparrow (Pooecetes gramineus), indigo bunting (Passerina cyanea), painted bunting (Passerina ciris) and scissor-tailed flycatcher (Tyrannus forficatus) when appropriate. Analysis of breeding season data is based on the 5 distance intervals, 0-25, 26-50, 51-100, 101-250, 251-499 meters). Analysis of fall covey data is conducted using exact distances from the survey point to covey, estimated using National Agricultural Imagery Program (NAIP) imagery in Arc GIS.

For breeding season species of interest that do not have adequate sample sizes to generate density estimates, we estimate relative abundances using a Poisson regression (with a log-link function). Pairwise random effects are included based on paired CP33 and control fields. Data sets with a consistent number of survey repetitions were treated with repeated measures random effects.

Program Distance Citation

Thomas, L., S.T. Buckland, E.A. Rexstad, J. L. Laake, S. Strindberg, S. L. Hedley, J. R.B. Bishop, T. A. Marques, and K. P. Burnham. 2010. Distance software: design and analysis of distance sampling surveys for estimating population size. Journal of Applied Ecology 47: 5-14. DOI: 10.1111/j.1365-2664.2009.01737.x