sentences:  The purpose of these parties is uncertain, but may include ascending to sleep on the wing, while still breeding adults tend to spend the night in the nest.Tracking swifts at their breeding colonies using radar has revealed that individuals often occur in flocks during dawn ascent and dawn descent but not during dawn ascent and dusk descent, suggesting that this flocking benefits the swifts via cue acquisition and information exchange between individuals or through extending social behaviour.Swifts may nest in former woodpecker tree burrows found in ancient forests, such as some 600 reported nesting in the Białowieża Forest of North Eastern Poland, or the small colony found in a combination of woodpecker holes and tree nestboxes on the RSPB's reserve at the Caledonian Forest in Abernethy, Scotland.