Seagulls in Puget Sound are known to crack open clams at low tide by dropping them on nearby rocks. Crows mimic the seagulls, but aren't always so accurate. It's funny, at the beach on foggy days (I heard it a lot on San Juan Island at the National Historic Park on the north end, English Camp). At low tide, the birds still feed, but more often when you hear a soggy "splat!" it is a crow that missed the rocks and hit wet sand when it dropped a clam. It's an eerie sound in the fog. :)

SRS