I took these photos at Bodensee and realised that the distance between these birds are very even, then I googled and found this answer on QUORA: If you note the distances over time, the initial distance is essentially "wing space;" the space between birds needed to land from flight and to take off using outspread wings. It's a very practical spacing that prevents wing collisions when landing or taking off. Once landed, certain species like to suggest together for warmth, social grooming, and so on, so the spacing shrinks. The spacing then is determined by family membership (families within a flock tend to rest together), social rankings, comfort, and factors less related to the need for wing space. Once a flocks starts to get the idea that they are about to move off the wire to go find food, continue a migration, etc., they begin to edge away from one another to obtain the space they need to spread their wings. -- Break The Mold Bird Bodensee