Possible Clues:

• Perch found in Shetland tidal water
• Bat's resting place
• Go out on a limb?
• Colony of bats; perch
• How to be underground around the South at night
• Sleep, as bird
• (Bird) settle for night
• The cock rules it
• (Bird) settle for sleep
• The bird may get up on this at 5 down