Life on the edge: Northern bobwhite ecology at the northern periphery of their range

Abstract

AbstractOver the past 40 years, Northern bobwhite (Colinus virginianus) populations have declined range‐wide. The Mid‐Atlantic once held the highest densities in the country and now shows some of the worst declines. Although population parameters have been quantified throughout most of the bobwhite range, Mid‐Atlantic populations have been largely unstudied. To better quantify the dynamics of this declining system, we sought to not only gather annual data on home range, movement, and habitat selection, but also examine how some of these metrics might impact survival. We captured and radio‐tracked 154 bobwhites between May 2006 and April 2008 on a 125 km2 area of Cumberland County, New Jersey, USA. Seasonal daily movement ranged from 146 m to 158 m but several extreme movements were notable. Across seasons, grassland habitat was used in greater proportion to its availability, shrub‐scrub and agriculture habitats were used equally with their availability and forests and other habitats were used less than their availability. Differences in second‐order selection occurred between seasons with lower use of shrub‐scrub and forest habitats and higher use of other habitat in breeding seasons. Pooled breeding season survival was 0.343, nonbreeding season survival was 0.183, and annual survival was 0.063. Although mortality was dominated by avian predators, house cat mortalities were noteworthy. Cox proportional hazard analysis revealed that risk of breeding season mortality risk was increased by longer daily movement, lower grassland use, and higher forest and other use. During the nonbreeding season, risk of mortality increased with shorter daily movement and proximity to occupied buildings and barns. This information could inform management decisions in the greater Mid‐Atlantic as well as other areas of their range where they exist at very low abundances. © 2010 The Wildlife Society.