Northern bobwhites (Colinus virginianus) are a culturally and economically significant game bird characteristic of grassland landscapes throughout their range. Despite the variety of research conducted on this species for nearly a century, populations continue to steadily decline, raising concern for future populations and highlighting the need for region-specific research. My research was conducted at Burning Star State Fish and Wildlife Area in northeastern Jackson County, Illinois from 2020-2022. My research addressed the following two objectives to provide insight on the population ecology of bobwhites at this site: (1) investigate the impact of multiple woody cover types within the home ranges of wintering bobwhites, how that cover may interact with winter severity, and their impacts on pre-breeding season survival, and (2) investigate the density of over-wintering diurnal raptor species between landscape types and discuss how this may be influencing predation risk. For objective 1, I radio-marked 141 individuals of which 102 had ≥ 15 relocations for estimating home-range size, and 127 individuals had ≥ 5 relocations and were used in survival analyses. I used an extended cox proportional hazards global model with continuous variables at the home-range scale. Variables considered included interspersion and juxtaposition index of blackberry, aggregation index of blackberry, and total area of blackberry, early successional forest, trees, and autumn olive. In addition, I used year, winter severity index (a time-dependent covariate), and an interaction term for year and winter severity index. The global model including all variables was retained as the most parsimonious model. Increases in the aggregation index of blackberry, area of autumn olive, and area of early successional forest were associated with increased hazard while increases in the interspersion and juxtaposition index of blackberry, area of blackberry, and area of trees were associated with a reduced hazard (α<0.05). For objective 2, I conducted 34 point-count surveys of predatory raptors throughout 6 landcover types every two weeks from October 2021 – January 2022. Bald eagles and barred owls were removed from analyses as I either did not credit them as significant predators of bobwhites or were nocturnal species, respectively. Observations from the 6 landcover types were split into two detection models based on whether the landcover type was classified as “open area cover” with a 125 m buffer distance or as “closed canopy cover” with a 75 m buffer distance. A uniform detection function was identified as the most parsimonious model for both the open area cover and closed canopy cover type models. Open area cover had a higher but not statistically significant difference in raptor density. My study demonstrates that woody cover types within the home-ranges of over-wintering bobwhites have strong relationships with the survival of those individuals and that diurnal raptors do not appear to be heavily concentrated in woody landscapes as predicted.

Northern bobwhite (Colinus virginianus) monitoring (e.g., covey-call surveys) is labor-intensive and imprecise. We evaluated the influence of bobwhite covey size and cover type on covey detectability when surveyed with a thermal camera-equipped small unmanned aerial system (sUAS). We placed bobwhite groups (3, 6, and 12 individuals/cage) among three cover types (grass, shrub, forest) on a private farm in Clay County, Mississippi (3 replicates, 27 total cages). At civil twilight, the sUAS flew over cages at 30 m, capturing photographs every 5 s. We asked 31 volunteers to evaluate 57 photographs for covey presence. Overall true positive rate was 0.551, but improved with increasing covey size. Coveys in grass had lowest true positive rate by photograph (0.403), followed by forest (0.562) and shrub (0.605). Results indicate that thermal sUAS could be a viable method for surveying intact bobwhite coveys, especially if detection of smaller groups and those in denser vegetation improves.

Northern bobwhite populations have declined concurrent with global warming. The focal period of this study was the 12-d pre-incubation period, when bobwhite eggs remain in the nest without the thermal protection of the incubating parent. This study first established the storage and thermal limits of bobwhite eggs, then investigated how global warming may impact oviparous embryos and how bobwhite embryos react to acute and chronic doses of simulated drought temperatures during pre-incubation. First, the maximum storage limit of bobwhite eggs was determined by storing eggs &#8804;21 d and measuring hatching success and pH of egg albumen and yolk. Hatching success of stored eggs declined after 14 d, when yolk and albumen pH reached levels detrimental to embryonic development. Secondly, thermal limits were determined by exposing bobwhite eggs to hyperthermic temperatures (38-52 °C). Bobwhite embryos survived 50 °C for 1 h, 49 °C for 3 h and 46 °C for 6 h. Results indicate an adaptation to the naturally occurring temperature extremes that can occur in the bobwhite's southern range during pre-incubation. Subsequently, bobwhite eggs were exposed to either low constant (LC), low fluctuating (LF), high constant (HC), or high fluctuating (HF) temperatures during pre-incubation to determine if the nature of temperatures differentially affected development. Although eggs exposed to high heat loads (HC and HF), and low heat loads (LF and LC) had equal heating degree-hours within groups, they exhibited differential growth during pre-incubation. Oxygen consumption, hatch timing, and hatching success were also affected by the thermal regimes. Eggs in simulated drought (HF) had a 47% lower hatch rate than eggs in simulated non-drought (LF) indicating that thermal stress during pre-incubation may contribute to population declines during drought. Finally, northern bobwhite eggs were exposed to acute or chronic doses of simulated drought temperatures, which tested for critical periods of development during pre-incubation. Collectively, data indicated that the earliest stages of bobwhite development were more affected by hyperthermic temperatures. Indeed, a critical period of development exists during the first 2/3 of pre-incubation during which exposure to hyperthermic temperatures results in aberrant development, hatching plasticity, and reduced hatch rates.