Possible Clues:

• 23 down would not have one of them so, sort of
• Of bird, settles for sleep
• The purchase of the birds,m by the sound of them
• The sound of purchase for the birds
• 'Rests on a perch, like a chicken (6)'
• So sort out for birds' perches
• Settles in for the night
• Birds finally settling in bits of trees (where they like to be)
• Places with a bird's-eye view
• Between-flight stops?