Replication Data for: Evidence for circadian-based photoperiodic timekeeping in the Svalbard ptarmigan, the northernmost resident bird.

The following data was used to generate the figures of the manuscript: \"Adaptive value of circadian rhythms in High Arctic Svalbard ptarmigan\". This includes data from in situ hybridisation (measured in optical density), raw activity data (measured in counts per minute), body mass, food intake and plasma testosterone levels. In addition we provide an overview over the experimental animals, the statistical analysis and the riboprobe sequences used for the in situ hybridisation.