I have some data on the foraging behaviour of a colonial seabird. Within the data there are clear sex differences in travel direction, but there is also an indication in preliminary plots that individuals display some consistency in their direction of travel- they are repeatable.
With this in mind, I wanted to know whether methods exist for the estimation of repeatability in a circular trait? As starting point, I assume I will be fitting a mixed effects model with a von mises distribution as the response, which I am able to achieve in brms/stan, but how I go from there to getting a measure of repeatability (an intra-class correlation coefficient) I am currently unsure.
many thanks for any input,
Jack
Like you mentioned mixtures of the von misses distribution is good for this data. I was wandering if the concentration parameter for each subgroup would indicate some kind of variation within each group and thus serve as measure of repeatability.
Von Mises is appropriate for the data. Then you can just compare standard deviations as a measure of repeatability, or use the concentration parameter, as Yohannes Afeworki Tecleab mentioned, since it is proportional to the evenness of the distribution :)
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