Conditional natal dispersal provides a mechanism for populations tracking resource pulses after fire

Animals that persist in spatially structured populations face the
challenge of tracking the rise and fall of resources across space and
time. To combat these challenges, theory predicts that species should use
conditional dispersal strategies that allow them to emigrate from patches
with declining resources and colonize new resource patches as they appear.
We studied natal dispersal movements in the black-backed woodpecker
(Picoides arcticus), a species known for its strong association with
recent post-fire forests in western North America. We radio-tracked
juveniles originating from seven burned areas and tested hypotheses that
environmental and individual factors influence dispersal distance and
emigration rates – investigating emigration while additionally accounting
for imperfect detection with a novel Bayesian model. We found that
juveniles were more likely to leave natal areas and disperse longer
distances if they were heavier or hatched in older burned areas where
resources are increasingly scarce. Juveniles were also more likely to
leave their natal burn if they hatched in a nest closer to the fire
perimeter. While dispersing across the landscape, black-backed woodpeckers
selected for burned forest relative to unburned available habitat.
Together, these results strongly support the hypothesis that black-backed
woodpecker populations track resource pulses across fire-prone landscapes,
with conditional natal dispersal acting as a mechanism for locating and
colonizing newly burned areas. Lending empirical support to theoretical
predictions, our findings suggest that changes in resource distribution
may shape dispersal patterns and, consequently, the distribution and
persistence of spatially structured populations.

栖息于空间结构化种群（spatially structured populations）的动物，面临着追踪时空维度内资源消长的挑战。
为应对此类挑战，相关理论预测物种应采用条件性扩散策略，使其能够从资源衰退的斑块中迁出，并在新的资源斑块出现时完成定居。
我们针对黑背啄木鸟（Picoides arcticus）的出生扩散（natal dispersal）行为展开研究——该物种以与北美西部近期过火森林的强关联性而广受认知。
我们对源自7处火烧区域的幼鸟开展了无线电追踪，并检验了环境与个体因素会影响扩散距离及迁出率的假说；同时借助一种新型贝叶斯模型（Bayesian model），在分析迁出行为时纳入了不完全检测（imperfect detection）的影响。
研究结果显示，若幼鸟体重更大，或是在资源愈发稀缺的老旧火烧区域孵化，它们更有可能离开出生区域并进行长距离扩散。
若幼鸟的巢穴距火边界更近，其离开出生火烧区域的概率也会更高。
在跨景观扩散的过程中，相较于未过火的可用生境，黑背啄木鸟会优先选择过火森林。
综合来看，这些结果有力支持了下述假说：黑背啄木鸟种群会追踪易火景观（fire-prone landscapes）中的资源脉冲（resource pulses），而条件性出生扩散正是其定位并定居新过火区域的核心机制。
本研究为相关理论预测提供了实证支撑，结果表明资源分布的变化或可塑造扩散模式，并进而影响空间结构化种群的分布与存续。