To build this dataset we merged records from 15 sources of data, listed in Extended Table 1. The way we mergre this database is described in the method part of the paper. Columns descriptor: Latitude and Longitude : WGS 84 coordinates Jday: Julian day of the record Species_mode: Species names and phenology mode (1,2,... or NA if the phenology is unimodal) Order: taxonomic order of the species Altitude: altitude got from spatial coordinates Source: Source of the data

Because of the protection of sensitive information about the exact location of recent populations of for instance rare butterflies to be available to everyone, we provide only 5x5km² location for data from the waarnemingen.be/observations.be databases.