The term PLUMP BIRD can be broken down into two crossword solutions: QUAIL (5 letters) and GROUSE (6 letters). QUAIL are small, plump birds that are found in many parts of the world. They have short wings and a round body, and they are often hunted for their meat. GROUSE are also small, plump birds that are found in North America, Europe, and Asia. They have short wings and a stocky body, and they are often hunted for their feathers.