Effects of broadcast feeding at multiple rates on the over-winter and annual survival rates of Northern Bobwhites (Colinus virginianus) in the Rolling Plains of Texas

The supplemental feeding of Northern bobwhites (Colinus virginianus) has long been debated as a practical technique to buffer quail populations through periods of climatic stress. With the species experiencing steady declines across their range over the past 50 years the necessity of cost-effective management programs has become paramount. On the Rolling Plains of Texas drought, livestock grazing practices, plant succession and periods of heavy rain and other climatic events have all driven the boom, bust cycle exhibited by the northern bobwhite. To address deteriorating populations several supplemental feeding techniques have been evaluated which include, most recently, broadcast feeding. Broadcasting feed is a relatively new technique designed to “broadcast”, or spread feed, throughout areas adjacent to roads. This practice allows birds to forage under the cover of surrounding vegetation and has had positive effects on annual survival rates of quail in Texas and the Southeast. The need to substantiate previous results and alter feed rates, which could potentially be cost prohibitive to smaller landowners, is necessary. My goals were to see if I could replicate earlier published survival results for this method while simultaneously reducing the overall cost to land and wildlife managers. I examined the effects of a broadcast feeding system at three different rates (Full Feed (~69.1 kg/km), Half Feed (~34.6 kg/km), and Control (no feed)) using grain sorghum on two separate range pastures on the 6666 Ranch in Guthrie, TX, 2013-2015. I used the Known-Fate data type in Program MARK to assess three different feed rates (treatments) and included covariates related to pasture, sex (male, female), age (juvenile, adult), and initial capture mass and the affect they had on estimates of over-winter (October 2013 - March 2014; October 2014 – March 2015) and annual survival (October 2013-September 2015). To assess the effects of my treatments on twelve, 404.6 ha units, I radiomarked 459 birds during the fall and winter of 2013 and 2014. The top models for both over-winter and annual survival contained the interaction parameter “Treatment*Year” (Wi = 0.848 and 0.395, respectively) and the interaction between “Treatment” and “Year” had a positive effect on survival. The “Treatment” parameter was determined to be the most important and carried >99.9% of the ΔAICC weight in both of our model sets. The model-averaged probability for surviving the over-winter periods (two years) was 45%, 52%, and 23% for our Full (~69.1 kg/km), Half (~34.6 kg/km), and Control (no feed) treatments, respectively. The model-averaged probability of surviving the annual periods (two years) was 17%, 25%, and 9% for our Full, Half, and Control (no feed) treatments, respectively. The separate pastures, different sex and age classes, and initial capture mass did not have any effect on survival within our model sets. I found the Half feed rate to be as effective as the Full rate and suggest it can be used to lower costs associated with implementation for wildlife managers and landowners. This study represents the third and fourth years of feeding and survival data on the 6666 Ranch and provides additional evidence that broadcast feeding is both a practical management tool for bobwhites and the most effective feed delivery method to date.