Temporal and scalar variations affect resource use of northern bobwhite broods

Abstract

Disparate resource use originating from phenology of biotic resources, abiotic conditions, and life cycles of exploiting organisms underscores the importance of research across time and space to guide management practices. Our goal was to evaluate resource use of northern bobwhite (Colinus virginianus; bobwhite) at two spatial scales and across three age classes, from hatching through a period of the postjuvenile molt. Our study was conducted at Tall Timbers Research Station, Tallahassee, FL, USA—situated in a landscape subjected to small scale (<20 ha) prescribed fires on a 2‐year fire rotation. We predicted prescribed fire, disking, and supplemental feeding would dictate resource use, but effects would depend on time since fire, brood age, and time of day. We predicted vegetation and temperature would govern roost use by broods, but these effects would also depend on age. We radio‐tracked 62 broods 21–35 times / week during May–October 2018 and 2019. Broods were less likely to use areas with large proportions of hardwood drains but favored sites with greater proportions of burned uplands, regardless of the time of day. Broods were less likely to use areas at greater distances from supplemental feed; this relationship had no interaction with age but was stronger later in the nesting season (>July 15). Broods were more likely to use areas with greater proportions of fallow fields during the day than for roosting. Broods used roosts with more woody cover and visual obscurity than at available sites. Roosts consisted of less grass and bare ground. However, these effects interacted with age; broods used sparser cover at older ages. Neonate broods were more likely to use cooler roosts with greater thermal stability, but this effect was reversed for juveniles. Broods may alter resource use with changes in vulnerabilities to threats such as thermal risks and predation.

Behavioral state‐specific resource selection of northern bobwhite chicks

“…and reported some similar results to ours, where they observed selection for areas closer to supplemental feedlines at the third-order scale (diurnal and nocturnal). Kubečka et al (2021) failed to detect an effect of age on feedline selection, whereas we observed a positive interaction between age and distance to feedline (i.e., younger birds were more likely to occur closer to feedlines) for foraging selection. This positive interaction is opposite of our prediction that older birds would be more likely to use these areas.…”

“…While there have been other studies examining the effects of supplemental feed on bobwhite resource use and movement, many have done so from Johnson's (1980) third‐ or second‐order scale; most of which were focused on suspected brooding adults (McGrath et al 2017), or brooding and non‐brooding adults (Sisson et al 2000, Buckley et al 2015, Wellendorf et al 2017). Kubečka et al (2021) were interested in the effects of supplemental feed on brood resource selection (regardless of brooding adult presence) and reported some similar results to ours, where they observed selection for areas closer to supplemental feedlines at the third‐order scale (diurnal and nocturnal). Kubečka et al (2021) failed to detect an effect of age on feedline selection, whereas we observed a positive interaction between age and distance to feedline (i.e., younger birds were more likely to occur closer to feedlines) for foraging selection.…”

“…One potential explanation for this could be the differences in use for feedlines between sites. Feedlines at the site investigated by Kubečka et al (2021) were primarily off-road trails through vegetation, whereas feed at our site was broadcasted off gravel and sand roads, sometimes used by heavy machinery and vehicles. Disturbances may occur in these areas more frequently relative to the aforementioned study site, causing decreased selection over time.…”

“…While there have been other studies examining the effects of supplemental feed on bobwhite resource use and movement, many have done so from Johnson's (1980) third-or second-order scale; most of which were focused on suspected brooding adults (McGrath et al 2017), or brooding and non-brooding adults (Sisson et al 2000, Buckley et al 2015, Wellendorf et al 2017. Kubečka et al (2021) were interested in the effects of supplemental feed on brood resource selection (regardless of brooding adult presence)…”

“…This lack of concealment for chicks at ground level during times when vigilance is low (roosting hours) would make them susceptible to predators that are nocturnal and crepuscular, such as eastern rat snakes ( Pantherophis alleghaniensis ) and corn snakes ( Pantherophis guttatus ; DeGregorio et al 2016), or meso‐mammals (Sunquist 1989, Chamberlain et al 1998). Kubečka et al (2021) reported that areas lacking a woody cover component, such as annually disked fallow fields, were less likely to be selected for as roost sites. The negative effect we reported between age and fallow field selection could be due to the naivety of younger birds, and as birds age and predator encounters persist in fields, birds may begin to develop a stronger avoidance for this land cover type as roosting habitat.…”