Possible Clues:

• Grouse from sailor putting Russian fighter into vessel
• Mountain grouse
• Variety of grouse
• It has white plumage in winter
• Bird also known as a snow grouse
• Arctic grouse
• Worm finally caught by a parting, wandering bird
• Game bird
• Bird got by sailor -- mighty, not half! -- in vessel
• Highland game bird — giant ramp (anag)