Xenospiza
Distracted
Hadn't noticed that (of course).The overview graph I posted is based on the maximum group size of swifts per square of the "TK25" topographical map, per 10 day period.
That should be pretty resilient against irregular reporting, except perhaps in very sparsely populated parts of the country.
My immediate next question is "How did you do that?" but don't burden this thread with that information!
While you're at it, if you'd plot the maximum group sizes against the TK25 coordinates, you might be able see if the average moves north or south and east or west through Germany.