Heterogeneity of locked-pasture snow conditions modulate habitat and movement choices of a facultative migrant, data archive

Habitat selection and movement are key mechanisms by which animals can
respond to and potentially cope with highly variable and rapidly changing
environmental conditions. Optimal responses likely vary, however,
depending on the severity and scope of limiting conditions. We tested this
hypothesis using a facultative migrant species, the Great Gray Owl (Strix
nebulosa), which exhibits high inter- and intra-individual variation in
the timing, direction, and distance of winter movements. Specifically, we
evaluated whether espisodic, spatiotemporally variable “locked-pasture”
snow conditions, which restrict access to subnivean food, prompted shifts
in habitat selection or long-distance movements by owls. We GPS-tracked 42
owls across the annual cycle within the Greater Yellowstone Ecosystem, USA
during 2017–2022. We used a novel ecological application of SnowModel, a
snow evolution modeling system, to estimate fine-scale, physical snow
properties likely to influence prey access. Variables included snow depth,
snow crusts produced by wind, and ice crusts produced by melt-freeze and
rain-on-snow events. Owls proximately avoided deeper snow and more severe,
heterogeneously distributed wind crusts via local shifts in habitat
selection. However, more widely distributed and persistent ice crusts
elicited long-distance movements away from affected home ranges.
Ultimately, the specific behavioral tactics employed varied with the
severity, spatial extent, and duration of limiting environmental
conditions. Our results provide a clear demonstration of behavioral
flexibility in response to extremely limiting, highly variable
environmental conditions. Such behavioral responses determine species
distribution, with implications for community dynamics in spatiotemporally
variable systems. Such understanding of responses to environmental
variability is increasingly important given the scope of on-going global
change.