The word waterbirds is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 17
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (46 words)
abiders, airbeds, arbiter, aridest, artsier, astride, baiters, barites, barters, bawdier, bedirts, bestrid, birders, braider, braised, braiser, brasier, darters, disrate, drawers, rabider, raiders, rarebit, rebaits, rebraid, redraws, retards, rewards, seabird, sidebar, starred, steward, stirred, strawed, strider, tardier, tarried, tarries, tirades, traders, waisted, waiters, warders, wariest, wartier, writers