There are six columns: 1. “year”: This variable indicates the year in which the bird was caught. 2. “season”: This variable indicates whether the bird was caught in spring or autumn. 3. "subsp": This is a factor with two levels. "leu" says that the bird belonged to the leucorhoa subspecies of the northern wheatear and "oen" says that the bird belonged to the oenanthe subspecies of the northern wheatear. 4. "Age.ad": This is a factor with two levels, i.e., "young" and "old". In autumn, "young" means 1st calendar year bird and "old" means that the individual was older than "young". In spring, "young" means 2nd calendar year bird and "old" means that the individual was older than "young". 5. "Sex": This is a factor with two levels. "1" says that the bird was a male and "2" that it was a female. 6. “direction”: This is the departure direction in degree
