Understanding the origin and function of introductory vocalizations before male zebra finch song

Abstract

Communication involves an exchange of information between the sender and receiver and for effective communication, animals have developed various displays. A number of these displays, in different species, begin with introductory gestures. An introductory gesture is not part of the main display and typically occurs at the beginning of the display. For e.g. Anolis lizards start their aggressive throat (dewlap) extension display with a few push-ups or tail flicks (Ord and Stamps, 2008) and frogs produce a single introductory note before their aggressive/advertisement vocalization (Schwartz and Wells, 1985; Wells and Schwartz1, 1984). Many different functions have been hypothesized for these introductory gestures, including an altering function before the main message (Richards, 1981), providing information for species recognition (Soha and Marler, 2000), and motor preparation for the main display (Rajan and Doupe, 2013). However, little is known about its properties, or origin, especially in the context of learned displays. In the course of my thesis, I have studied the properties and origin of the introductory notes before the song of the zebra finch, a well-studied Australian songbird. The song of the male zebra finch consists of a stereotyped sequence of sounds (syllables) that the young bird learns from a tutor. Song bouts begin with a variable number of short-duration vocalizations called introductory notes (INs). Previous work has suggested that these INs serve as motor preparation for song production (Rajan and Doupe, 2013). However, whether INs are learned or not, how they are produced by the brain, and what function they serve, remains poorly understood. Through my thesis work, I have addressed each of these questions. First, using different tutoring methods, I have shown that the acoustic properties of INs, and the mean number of INs before song, are learned from the tutor in the same way as song is learned.