The term 'small singing bird' can be summarized by two crossword solutions: WREN (4 letters) and PIPIT (5 letters). Wrens are small, brown birds with a short tail and a loud, melodious song. They are found in many parts of the world, including North America, Europe, and Asia. Pipits are also small, brown birds with a long tail and a sweet, warbling song. They are found in grasslands and open woodlands in Europe, Asia, and North America.