American Cliff Swallow (Petrochelidon pyrrhonota) Science Article 2
abstract
Unlike many other woodpeckers that feed on woodboringinsects and larvae, Acorn Woodpeckers (MeIanerpes formicivorus) feed primarily on acorns, insects caught by flycatching, and sap (Bent 1939, MacRoberts 1970, MacRoberts and MacRoberts 1976). They also supplement their diets with an occasional small lizard (Koenig, pers. comm.), fruit, oak catkins, and wild oat seeds (MacRoberts and MacRoberts 1976)
ERIC D. FAJER, KAREN J. SCHMIDT AND JAMI G. ESCHLER, The Condor 89:177-178