Influence of Aridity and Weather on Breeding-Season Survival of Northern Bobwhites in South Texas, USA

Abstract

Abstract Understanding vital rates of wildlife populations is essential for developing realistic management objectives. We conducted an analysis of data from four northern bobwhite Colinus virginianus research projects conducted in South Texas to examine the extent that environmental factors (total seasonal precipitation, mean maximum seasonal temperature, growing-season length, and Keetch–Byram drought index values) influenced survival during the 5-mo (April–August) breeding season. We constructed generalized logistic mixed models and compared them using Akaike's Information Coefficient to rank their parsimony. Our selected model (cumulative breeding-season survival = bobwhite sex + growing season length [days of photosynthetic activity] + Keetch–Byram Drought Index score [averaged from April to August] + site-specific effects of each ranch) explained 35.3% of the total variation in the data set. Breeding season survival was positively related to growing season length (β = 0.01, 95% CI = 0.00–0.02), and negatively related to Keetch–Byram Drought Index score (β = −0.01, 95% CI = −0.01 to −0.01; rounded to two digits). Managers cannot control weather, but the ability to account for nearly one-third of variation in breeding season survival from weather, sex, and site-specific effects of the ranch refines our understanding of factors that influence bobwhite population dynamics in South Texas.