Environmental and seasonal correlates of capercaillie movement traits in a Swedish wind farm

Animals continuously interact with their environment through behavioural
decisions, rendering the appropriate choice of movement speed and
directionality an important phenotypic trait. Anthropogenic activities may
alter animal behaviour, including movement. A detailed understanding of
movement decisions is therefore of great relevance for science and
conservation alike. The study of movement decisions in relation to
environmental and seasonal cues requires continuous observation of
movement behaviour, recently made possible by high-resolution telemetry.
We studied movement traits of 13 capercaillie (Tetrao urogallus), a mainly
ground-moving forest bird species of conservation interest, over two
summer seasons in a Swedish windfarm using high-resolution GPS tracking
data (5-minute sampling interval). We filtered and removed unreliable
movement steps using accelerometer data and step characteristics. We
explored variation in movement speed and directionality in relation to
environmental and seasonal covariates using Generalized Additive Mixed
Models (GAMMs). We found evidence for clear daily and seasonal variation
in speed and directionality of movement that reflected behavioural
adjustments to biological and environmental seasonality. Capercaillie
moved slower when more turbines were visible and faster close to turbine
access roads. Movement speed and directionality were highest on open bogs,
lowest on recent clear-cuts (<5 y.o.) and intermediate in all types
of forest. Our results provide novel insights into the seasonal and
environmental correlates of capercaillie movement patterns and supplement
previous behavioural observations on lekking behaviour and wind turbine
avoidance with a more mechanistic understanding.