The size of a non breeding flock of Mute Swans Cygnus olor on a water body near Kwiecewo was much higher in spring than in summer. The decrease in the number of birds was likely to be due to local movements associated, among other things, with the gradual shrinking of water surface and flying to moulting grounds. More intensive foraging in spring could be a result of higher food requirements at lower temperatures. In summer, more birds were preening feathers, which could be related with moulting at that time. In both spring and summer, highest numbers of Swans foraged in the evening, rather than in the other times of the day.
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