recur is a special form (i.e. not implemented as a function or macro). It handles the case of the self-recursive call whereas the trampoline handles the mutual

recur is a special form (i.e. not implemented as a function or macro). It handles the case of the self-recursive call whereas the trampoline handles the mutually recursive call. There is no generalized tail call facility in the JVM and therefore not in Clojure.