Field test of assumptions for using line transect distance sampling on Rock ptarmigan

not-yet-known not-yet-known not-yet-known unknown Reliable population estimates are essential for the management of harvested species. Line transect distance sampling using pointing dogs has been proposed for monitoring of rock ptarmigan. In this study we test assumptions of line transect distance sampling: (i) That birds on the transect are detected with certainty and (ii) birds are detected at their initial location. We also investigated factors potentially influencing the detection probability. We conducted experiments in 2022 and 2023, by walking towards GPS-tagged rock ptarmigans, accompanied by a pointing dog. Our result shows that all rock ptarmigans within 0-30 m from the transect were detected with certainty. It was more likely that birds became passive after being active than the opposite as the dog and handler approached it. The birds were found close to their initial position, also in situations where they became active as the dog and handler approached it. The best models to explain detection probability included the bird’s distance to the transect and distance moved. The distance to the transect had a strong negative effect, which is expected in line transect distance sampling designs. The distance the bird moved from its initial location had a weak positive effect on detection. This might indicate that birds are more likely to be detected if they are on the move. Models with other external factors had less support. Our results indicate that line transect distance sampling using pointing dogs does not violate the key assumptions when applied on rock ptarmigan. Based on these results, we suggest that the existing line transect survey design for willow ptarmigan is extended in altitude to also cover rock ptarmigan habitat, and that further investigation is needed to assess the usefulness of covariates to improve estimates.