Related Clues:

• "One Flew Over the Cuckoo's ---"
• Fit one inside the other
• Fit one inside another
• Roost
• Hobbyist's place
• Refuge
• Fit well together
• Brooding place
• Winter home, maybe
• Treetop retreat
• Household retreat
• Cubby hole?
• Place of concealment
• Hotbed
• Place for fresh eggs