Temporal and scalar variations affect resource use of northern bobwhite broods

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 locally relevant 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 post-juvenile molt. Our study was conducted at Tall Timbers Research Station, Tallahassee, FL, USA– situated in a pyric landscape subjected to biennial prescribed fire. 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. The effect of supplemental feed 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.

由生物资源物候、非生物环境条件以及利用该资源的生物的生命周期差异所引发的资源利用分化，凸显了开展跨时空研究以指导因地制宜的管理实践的重要性。本研究旨在从孵化期至幼羽换羽后期，在两种空间尺度下，针对三个年龄层级的山齿鹑（northern bobwhite，*Colinus virginianus*，后文简称鹑群）的资源利用情况进行评估。本研究于美国佛罗里达州塔拉哈西市的高木研究站（Tall Timbers Research Station）开展，该区域地处以每两年一次计划性火烧为主要干扰的火调控景观之中。本研究提出两项核心假设：其一，计划性火烧、翻耕作业与补充投喂将主导鹑群的资源利用，但这些影响效应会受火烧后时长、鹑群日龄以及当日时段的调控；其二，植被与温度将决定鹑群的栖息位点选择，且该效应同样会随日龄变化而改变。2018年与2019年5月至10月期间，研究团队每周对62个鹑群进行21至35次无线电追踪。研究结果显示：无论当日时段如何，鹑群均较少利用阔叶树排水带占比高的区域，但更偏好高地火烧占比更高的位点；鹑群对距离补充投喂点越远的区域的利用概率越低，且该相关性未受日龄的调控；补充投喂的影响效应在繁殖季后期（7月15日之后）更为显著。相较于栖息时段，鹑群在日间更倾向于利用休耕地占比更高的区域。相较于可利用的随机位点，鹑群所选择的栖息位点拥有更高的木本覆盖度与视觉遮蔽度，且栖息位点内的草本与裸地占比更低。但上述效应会随日龄产生交互变化：日龄更大的鹑群会选择覆盖度更低的栖息位点。新生鹑群更倾向于选择温度更低、热稳定性更强的栖息位点，但该效应在幼鹑阶段发生逆转。鹑群可能会根据自身面临的热胁迫与捕食等威胁的脆弱性变化，调整其资源利用策略。