Territorial dynamics of Mexican Ant-thrushes Formicarius moniliger revealed by individual recognition of their songs ALEXANDER N. G. KIRSCHEL, 1,2 * † MARTIN L. CODY, 2 ZACHARY T. HARLOW, 2 VASILIS J. PROMPONAS, 1 EDGAR E. VALLEJO 3 & CHARLES E. TAYLOR 2 1 Department of Biological Sciences, University of Cyprus, PO Box 20537, Nicosia 1678, Cyprus 2 Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, CA, USA 3 Department of Information Technologies and Computer Science, ITESM-Campus Estado de Me´xico, Estado de Me´xico, Mexico The ability to monitor interactions between individuals over time can provide us with information on life histories, mating systems, behavioural interactions between individu- als and ecological interactions with the environment. Tracking individuals over time has traditionally been a time- and often a cost-intensive exercise, and certain types of animals are particularly hard to monitor. Here we use canonical discriminant analysis (CDA) to identify individual Mexican Ant-thrushes using data extracted with a semi-automated procedure from song recordings. We test the ability of CDA to identify individuals over time, using recordings obtained over a 4-year period. CDA correctly identified songs of 12 individual birds 93.3% of the time from recordings in one year (2009), while including songs of 18 individuals as training data. Predicting singers in one year using recordings from other years indicated some instances of variation, with correct classification in the range of 67–88%; one individual was responsible for the great majority (66%) of classifica- tion errors. We produce temporal maps of the study plot showing that considerably more information was provided by identifying individuals from their songs than by ringing and re-sighting colour-ringed individuals. The spatial data show site fidelity in males, but medium-term pair bonds and an apparently large number of female floaters. Recordings can be used to monitor intra- and intersexual interactions of animals, their movements over time, their interactions with the environment and their population dynamics. Keywords: bird song, individuality, neotropics, spatial and temporal dynamics. Birds use their song for long-distance communica- tion. The song is typically loud enough to be heard by individuals in neighbouring territories and thus functions to advertise to neighbours that territories are occupied (Wiley & Richards 1982). Ecologists have often used song for identifying movement patterns and locations of birds to infer territory size and likely locations of territory boundaries (e.g. Falls 1981, Morton et al. 2000, Fedy & Stutchbury 2004). However, if males and females both produce similar songs, differentiating between communications within a mated pair and an intrasexual interaction between rivals can be challenging. Furthermore, without analysis of individual variation in song it is not possible to assess whether resident territory holders are the same birds from 1 day, week or season to the next, without some form of individual marking. Thus, to gain a better understanding of territory dynamics in birds, researchers have typically mist-netted and colour-ringed birds, and then conducted extensive surveys to observe the colour-ringed individuals as they move through their territories (e.g. Greenberg & Gradwohl 1986, 1997). Colour-ringing every individual within a study plot and conducting surveys to monitor individuals *Corresponding author. Email: kirschel@ucy.ac.cy †Present address: Edward Grey Institute, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK. ª 2011 The Authors Journal compilation ª 2011 British Ornithologists’ Union Ibis (2011), 153, 255–268