DAWN SONG REPERTOIRES OF TREE SWALLOWS (TACHYCINETA BICOLOR)

I describe the dawn songs of 38 male tree swallows (Tachycineta bicolo r) recorded at five sites near Wolfville, Nova Scotia. Males deliver d awn song each morning during the hour before dawn, while flying ellipt ical paths above their nest sites. These dawn songs consist of syllabl es approximately 0.15 s long, delivered every 1.5 s. Each male has a r ecorded repertoire of one to seven discrete syllable types (average 2. 6) and may repeat each syllable type an apparently random number of ti mes before switching to the next. Most syllables could be classified o n the basis of their structure into seven types, with much variation a mong renditions by different males of any given syllable type. Three o f these syllable types were very similar to call notes that have speci fic uses at other times of day. Syllable types were randomly distribut ed among males and sites. In this species neither syllable type, the n umber of times each type is repeated (string length), nor the number o f types a male sings (repertoire size) appears to carry particular mes sages or advertise male quality. Instead, syllable types may provide i ndividual distinctiveness and variety in song sequences.