This video is called Common swift (Apus apus) under some tiles and flying.
Translated from the Dutch SOVON ornithologists:
Friday, August 28th, 2015
Swifts stay no longer in our country than is strictly necessary. Almost immediately after the fledging of the youngsters they disappear towards Africa, mostly in the second half of July. This year in the end of August there was a late wave of Scandinavian migrating birds. Exceptional!
Migration counters record most swift movements in the second half of July. Normally the numbers of swifts fall sharply in early August. The migration then trickles on a bit, with the last birds passing in September or even October
In the fourth week of August this year there were strikingly many swifts seen by migration counters. Especially on August 23 sizable numbers were recorded: 1272 in Bergen aan Zee, 1084 at De Nolle in Vlissingen, 576 at the Volcano in The Hague and 563 in Ketelbrug.