Data and R-script to analyse timing of northward migration of Sanderlings (Calidris alba) through Europe

The data file contains data of observations of individual Sanderlings (Calidris alba) from specific wintering areas observed during migration in different latitude sectors through Europe. This is a subset of the raw data file which also includes observations at the wintering grounds. Each individual is indicated with a unique number in column “Individual”. The column “Winter Area” indicates the winter location of each individual in sectors of 5 degrees latitude (as depicted in Fig. 1 in the manuscript), with 7 indicating Scotland, 8 England, 9 France, 10 North Iberia, 11 Portugal, 13 Canary Islands, 15 Mauritania, 18 Ghana and 23 Namibia, as indicated in the column “Winter_Country”.  “Date_DOY” indicates the day of year on which current observation was made. “Year” indicates the year during which an observation was made, “lat” is the latitude and “lon” the longitude of each observation in decimal degrees. “Lat_Sector” specifies in which of the sectors of 6 latitudinal degrees in Europe  (see Fig. S1) the observation was made. “Sex” indicates the sex, based on molecular methods of an individual where 0=unknown, 1=female, 2=male. “Age”is the age of an individual, where 50=juvenile (i.e. less than 1 year old), 99=adult (i.e more than 1 year old) and 0 indicates that the age was unknown. “migration” indicates whether an observed individual is conisdered to be on migration (“yes” i.e. seen at least 2 latitudinal degrees north of its average winter location) or not (“no”). Further details can be found in the methods section in the manuscript.

The R-script uses this dataset to analyse the variation in timing of migration through Europe for individual Sanderlings from different non-breeding areas. Comments and explanations can also be found in the script and in the methods section of the manuscript.