Related Clues:

• Like Matryoshka dolls
• Incubation site
• Home in a 45-Across
• Like some Russian dolls
• Kind of egg
• "One Flew Over the Cuckoo's ---"
• Fit one inside the other
• Fit one inside another
• Roost
• Fit well together
• Brooding place
• Treetop retreat
• Like Russian dolls
• Hotbed
• Place for fresh eggs