What’s in a song? A quantitative description of the veery’s (Catharus fuscescens) complex song repertoire

Background/Question/Methods The veery (Catharus fuscescens) is a neo-tropical migratory thrush species with a beloved, unusual sounding song. Like many thrushes, their vocalizations are complex; however their song has remained largely unstudied since the early 1970s, and these early studies were qualitative, relying on very small sample sizes. We have observed that veeries combine sets of notes to create a variety of songs that vary in note number, order and composition in ways that have not yet been fully quantified. In this study, we aim determine: (1) The number of different notes each male sings and how he combines them in his songs and (2) The extent that these notes and songs are shared among male veeries. To achieve this, we recorded several samples of natural singing from over 30 individual veeries on the grounds of the Cary Institute of Ecosystem Studies, from May through August of 2009.  In 2014 we used Raven Pro 1.4 software to visually categorize all of the notes into 22 distinct types based on the shape of their sonograms, which indicate differences in note duration, frequency, and amplitude. We then cut the examples of the note types from whole songs, and compared them against one another using Sound Analysis Pro 2011.  This software compares all of the notes in terms of both amplitude and mean frequency yielding an objective, computer-generated percent similarity score for each pairwise comparison of notes.

Results/Conclusions Visual analysis in Raven Pro 1.4 revealed that veeries sing an average of about 4 different notes types per song resulting in 6 total notes per song because some note types are repeated. 10 of the 22 note types that we identified were shared among two or more male veeries and 12 notes were considered unique to an individual veery. Our automated computer analysis is providing percent similarity scores ranging from 37.92% to 93.79% for our visually-perceived note types, and will allow us to distinguish which note types are truly distinct, and which ones are shared among males. The results of this study will help us understand more about how veeries communicate, and will lay the foundation for further studies of the function of both unique and shared song types as males defend their territories and attract their mates. Understanding how these songbirds communicate will allow us to better monitor reproduction, which affects our ability to create appropriate conservation strategies for this and other vulnerable species.