NOTE: The raw data are available from the Global Population Dynamics Database as 25 separate species datasets (Dataset ID 9742:9766). Not sure how, where and when these were put together into the raw dataset in our repo: data/raw_datasets/dataset_70.csv
The Belgian Migrating Lepidoptera Survey (originally at http://www.club.innet.be/~pub00644, but now only available through archive.org: (https://web.archive.org/web/19990220041409/http://users.skynet.be/bs663526/)
For an analysis validating core-transient designations based on temporal occupancy, we can use the author's (semi)-independent classification of species in Belgium here: https://web.archive.org/web/19991004203758/http://users.skynet.be/bs663526/list.htm
NOTE: The raw data are available from the Global Population Dynamics Database as 25 separate species datasets (Dataset ID 9742:9766). Not sure how, where and when these were put together into the raw dataset in our repo: data/raw_datasets/dataset_70.csv