The application of lidar in woodland bird ecology: climate, canopy structure, and habitat quality

Habitat quality is fundamental in ecology, but is difficult to quantify. Vegetation structure is a key characteristic of avian habitat, and can play a significant role in influencing habitat quality. Airborne lidar provides a means of measuring vegetation structure, supplying accurate data at high post-spacing and on a landscape-scale, which is impossible to achieve with field-based methods. We investigated how climate affected habitat quality using great tits (Parus major) breeding in woodland in eastern England. Mean chick body mass was used as a measure of habitat quality. Mean canopy height, calculated from a lidar digital canopy height model, was used as a measure of habitat structure. The influence of canopy height on body mass was examined for seven years during which weather conditions varied. The slopes and correlation coefficients of the mass/height relationships were related linearly to the warmth sum, an index of spring warmth, such that chick mass declined with canopy height in cold, late springs, but increased with height in warm, early springs. The parameters of the mass/height relationships, and the warmth sum, were also related linearly to the winter North Atlantic Oscillation index, but with a time lag of one year. Within the same wood, the structure conferring “best” habitat quality differed between years depending on weather conditions.