(1) Each of the three species of Sayornis employs some of its vocal displays in more or less continuous, regular, and prolonged bouts which, for present purposes, are defined as "song". In each species, song is a complex form of displaying comprising various combinations of two to three basic displays, the Regularly Repeated Vocalizations (RRVs, with units RR1 and RR2) and the Initially Peaked Vocalizations (IPVs). (2) Within each species, the basic display units differ from one another in the behavior patterns with which their employment can be correlated; that is, each display differs in message from the others. Since song comprises various combinations of these displays, its message is variable and dependent upon their ratio in each combination. (Whether or not the message of song varies in direct proportion to the frequency of its components has not been measured.) Yet the general range of employment of song bouts appears to be similar from species to species, indicating that the range of messages available to song is also generally similar. The song messages indicate different probabilities that the communicator will attack or escape, be nonagonistic, or associate; they also identify the communicator. (3) The messages of at least the RR1 and IPV displays vary among the species, so that the use of these displays in song also varies among the species. IPV is rarely or never used in song bouts of S. phoebe, but is prominent in the song of S. nigricans, and is the major component of S. saya song in which the RR1 is used very little. Many of the behavioral patterns with which the use of IPV is correlated in S. nigricans (and apparently in S. saya, for which the data are less extensive) are correlated with use of the RR1 in S. phoebe.