A cryptic new species of flycatcher (Tyrannidae : Suiriri) from the cerrado region of central South America

A new species of tyrant flycatcher (Siororo islerorum) is described from th e cerrado region of Brazil and adjacent eastern Bolivia. The species previo usly had been confused with Suiriri suiriri affinis, with which it is synto pic at multiple sites. The new species was first identified by voice. Altho ugh cryptically similar to S. s. affinis in many respects, the new species is readily identified by ail vocalizations, bill size, color pattern of the tail, and shape of the central rectrices. Most distinctive are the male-fe male duets, which are accompanied by dramatic wing-lifting displays not per formed by any congeners. Reciprocal playback experiments of tape-recorded v ocalizations demonstrated that the new species and S. s. affinis do not res pond to one another's vocalizations. We provide information on thr natural history of the new flycatcher, along with spectrograms of its various vocal izations. We also provide vocal analysis of all other named taxa in Suiriri , and discuss the various intrageneric relationships. In particular, S. s. affinis and S. s, bahiae, although distinct morphologically, are vocally an d behaviorally similar, and respond to one another's vocalizations in playb ack experiments.