Geese
Well as i wrote below i forgot to shoot a pic of the sky. But then remembered something else.
Shot this pic last year in the time when much birds migrate to the south. Its a search pic but you see the typical V form below. One cant only see but also hear them. In the fog last week i made a soundrecording of overflying geese. Because of the fog they probably got disoriented so they fly low and maby towards the lights of the city too. You can find the recording here. Maby they even yell more so they dont get lost from the group. Btw im not sure if the birds in the pic above are geese.
Zoom of the V (although im not sure i shot this pic on the same day)
For the people who couldnt find the birds on the pic above.