This distinctive species is more often heard than seen. It is the sole member of the genus Tyrannulus. It may be related to the Forest Elaenia (Myiopagis gaimardii). Both were formerly placed in the Cotingidae based of their incomplete tarsal envelope. The yellow crown is concealed and difficult to see.
Reference:
Fitzpatrick, J. (2004). Yellow-crowned Tyrannulet (Tyrannulus elatus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/57133 on 23 September 2015).
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