Disturbance-related redistribution of Western capercaillie (Tetrao urogallus) away from woodland tracks

Wild vertebrates usually avoid ground disturbed by humans with uncertain effects on their distribution and density. We report on a natural experiment that confirms and extends previous conclusions about how the local distribution of capercaillie is affected by track-based disturbance. We surveyed the birds’ droppings in two periods, before and after a predicted increase in disturbance adjacent to an expanding Scottish village, and model the probability of finding droppings in relation to period plus two disturbance gradients – distance to a much disturbed ‘entry zone’ with a high density of tracks lying adjacent to the village, plus distance to the nearest track. Throughout the study, no droppings were found within the entry zone and their density was depressed up to 400 m from it. Density of droppings was also depressed within 100–120 m of tracks but, compared to a notional scenario without tracks, was threefold greater on ground 120–250 m from tracks. Although the number of cocks coun..., Capercaille droppings were surveyed along fixed N-S transects 100m apart during 14 surveys in 2006-2021. These fell into two periods: Period 1 before the adjacent housing development and Period 2 after it.  Each observation was assigned to a 100 x 20m grid based on the transect lines. These observations were then used to prepare the heat map Figure 1. The distances from each grid point to the 'entry zone' dE and to the nearest track dT were measured via GIS. The probability of finding droppings Pf (response variable) was then modelled as (explanatory variables) a cubic polynomial in dE and a quadratic in dT plus the category period and its interactions with each of the polynomial terms via  the SAS (ver 9.1) Glimmix macro to enact a logistic GLMM with survey as a random effect. Temporal and spatial autocorrelations were accounted for as explained in the paper., , # Disturbance-related redistribution of Western Capercaillie Tetrao urogallus away from woodland tracks

## BoG data WLB-2023-01151.R2

The data are on an Excel file with three worksheets:

Droppings 2006-21

entry_zone_distances_dE

track_­distances_dT

**Droppings 2006-21** contains the positions and other details of each observation of droppings. Each column is headed by a short title with an associated explanatory note. \".\" in a cell denotes no data.

**entry_zone_distances_dE** contains the positions (easting and northing) of each grid point within the main study area plus the distance dE to the entry zone. Each column is headed by a short title with an associated explanatory note.

**track_­distances_dT** contains the positions (easting and northing) of each grid point within the main study area plus the distance dT to the nearest track. It includes distances to old tracks that were present throughout  (column D,  t_dist (dT)) plus distances that include the new tracks of Period...