INFLUENCE OF LANDCOVER ON NORTHERN BOBWHITE HOME RANGE AND SURVIVAL AT MULTIPLE SCALES IN SOUTHERN ILLINOIS

Author

Caleb Stanley Crawford, Southern Illinois University CarbondaleFollow

Date of Award

9-1-2021

Degree Name

Master of Science

Department

Zoology

First Advisor

Eichholz, Michael

Abstract

Northern bobwhite (Colinus virginianus) populations have continually declined across much of their native range due to changes in land use and habitat. This notable decline causes concern for the future of this important game bird species and highlights the need for research on how habitat influences bobwhite vital rates. My research, conducted during 2018-2020 at Burning Star State Fish and Wildlife Area, addressed the following two objectives to provide information on how landcover characteristics influence bobwhite populations: (1) investigate how landcover characteristics influence annual bobwhite home range size, and (2) investigate how landcover characteristics influence bobwhite breeding season survival. For Objective 1, I radio-marked 113 individuals of which 50 bobwhites (31 males and 19 females) had ≥25 independent tracking locations and were used in my analyses. I modeled landcover types related to bobwhite habitat selection, habitat avoidance, foraging habitat, and protective cover to annual bobwhite home range size. Landcover types related to foraging habitat formed the most parsimonious model, with the proportion of grassland having the greatest negative influence on bobwhite home range size. As expected, landcover types that are thought to be beneficial to bobwhite fitness were negatively related to bobwhite home range size, suggesting those landcover types provide necessary resources for bobwhites throughout their full annual cycle. For Objective 2, I radio-marked 113 individuals of which 50 bobwhites (31 males and 19 females) had ≥25 independent tracking locations and were used in my analyses. I used a known fate model of the influence of landcover types, in a stepwise fashion, on bobwhite breeding season survival at two scales, home range and landscape. At the home range scale, the univariate model including early successional forest was the most parsimonious model, wherein the proportion of early successional forest negatively influenced bobwhite breeding season survival. Other competitive models included agriculture and early successional forest + scrub shrub where agriculture positively influenced breeding season survival while early successional forest and scrub shrub negatively influenced breeding season survival. The negative influence of landcover types thought to provide necessary protective cover for bobwhites on breeding season survival is inconsistent with the current paradigm that woody cover is an important habitat component that provides protective and escape cover, thermoregulatory functions, and midday loafing sites for bobwhites. Early successional forest provides visually appealing woody protective cover but appears to expose bobwhites to a higher predation risk because trees provide perch habitat for avian predators. Agriculture positively influenced breeding season survival because during the breeding season, agriculture provides overhead cover and bare ground that provides protective cover, foraging opportunities, and enables ease of movement. At the landscape scale, the null model was the most parsimonious model, but there was weak evidence that the proportion of grassland positively influenced breeding season survival. My study demonstrates how landcover composition influences annual home range size and breeding season survival at different scales.