Line transect distance sampling using pointing dogs, is an established survey method for willow ptarmigan and has also been proposed for monitoring of rock ptarmigan. In this study, we tested assumptions of line transect distance sampling that: (i) birds on the transect are detected with certainty and (ii) birds are detected at their initial location. We also investigated factors potentially influencing detection probability. We conducted field experiments in 2022 and 2023, by walking line transects while accompanied by a pointing dog, towards GPS-tagged rock ptarmigans. All rock ptarmigans within 0-30 m from the line transect were detected with 100% certainty. All birds were found close to their initial position, and most birds were passive (74%) as the surveyors approached. The best models to explain detection probability included the bird’s distance to the transect and the time of day an experiment was conducted. The distance to the transect had a strong negative effect, which is expected in line transect distance sampling designs. The time of day when conducting experiments also had a non-linear effect on detection probability, with lower detectability during midday compared to the morning and evening .

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