Possible Clues:

• Bird in addition reveals chest part
• Problem preserving aquatic bird's bone
• In addition, bird has a breastbone
• Bird in addition shows chest part
• A few mentioned pinching diver's bone
• Munster (anag) — flat bone in the chest
• It's found between breasts and rear ends when one goes topless
• Problem keeping Arctic seabird's bone
• Problem with seabird penetrating bone
• Bone in bird swallowed by tot