Brown Noddy (Anous stolidus) Science Article 3
abstract
Three steps are necessary in the study of avian vocal repertoires (aside from developmental and physiological aspects) (.1) The various vocalizations and the situations (context) under which they are given must be identified and described under natural conditions. The description should be objective enough so the calls can be readily recognized by other observers
NICHOLAS E. COLLIAS, The AUK, vol. 105