Originally posted by UncleVanya More likely trying to break the shell.
Much the same thing. SFAIK kingfishers always swallow their food whole rather than picking (pecking) at it a little bit at a time. At another place we observed a kingfisher treating a small fish the same way, slapping it repeatedly on a hard surface, a rock as I recall but I'll need to look at the pictures to be sure. It's almost certainly a stereotyped behavior and although I suggested "tenderizing" the purpose may be to literally beat the life out of the prey before it is swallowed, making sure that it isn't just merely dead, it really is sincerely dead.