Investigating the use of covey call point counts to estimate autumn density of northern bobwhites

Early morning point counts of northern bobwhite (Colinus virginianus) coveys have been conducted in autumn to estimate post-recruitment abundance of northern bobwhite coveys. However, the value of this index method is limited due to an inability to meet critical assumptions and an unknown relation to density. Models of covey detectability could be used to adjust point count data and obtain an unbiased estimate of density. Therefore, we measured detection rates of calling coveys and used program DISTANCE to develop a detection function and density estimate for 2 study areas in north Florida, USA. The overall observer detection rate was 0.94 for 0–100 m, 0.89 for 100–250 m, 0.41 for 250–500 m and 0.03 for observations > 500 m. Detection variability was highest between 250–500 m. A uniform function was the selected best model and was used to generate density estimates, but fit was marginal (P < 0.05). Density estimates generated from point count data were similar to density estimates from an intensive quadrant survey technique. Point count surveys can be an effective method to estimate autumn density of northern bobwhite if adjusted by functions of detectability.