Who's who of palm cockatoos : evaluating non-invasive techniques for identification of individual palm cockatoos (probosciger aterrimus)

Abstract

Knowledge of individual identity within populations is often essential for obtaining a detailed understanding of the ecology and conservation requirements of species. Palm cockatoos (Probosciger aterrimus) are extremely difficult to catch and are susceptible to over-stress. As such, a non-invasive alternative to traditional capture techniques is highly needed. This thesis primarily investigates vocal individuality as a non-invasive technique for this species. First, I developed a naming system for palm cockatoo vocalisations to organise and verbally described them all. I used advanced sound recording equipment and sound analysis technology to quantify call parameters, such as multiple temporal, energy (amplitude), and frequency measurements on the spectrogram. Using this data, I performed multivariate analysis to classify distinct syllables and determine the number of discrete syllables in their vocal repertoire (27). In this process, I found that palm cockatoos have an unusually large vocal repertoire for a parrot (Psittaciformes) and that they enhance vocal complexity by combining multiple syllables to create longer and more varied vocalisations. Although most syllables (19/27) in the repertoire were used in this manner, this vocal technique occurred exclusively in two behavioural contexts: display and call-exchange with intruders. The process of combining vocal units to form more complex vocalizations is analogous to the formation of songs in many passerines. Further, the contexts in which palm cockatoos produce complex calls appear to be the same as the main contexts in which passerines sing. I propose that these similarities might have evolved through convergent evolution to facilitate territorial defence in both palm cockatoos and many passerines. I then showed that palm cockatoos are individually distinctive in their call structure for three discrete call types: 85.6% of calls, or 137 out of 160, were assigned to the correct individual. However, a small sample of five birds recorded over several months, together with three birds recorded over one year, suggests a lack of vocal stability within individuals over time. For this reason, as well as due to various logistical aspects, I recommend against using the call-dependent (comparing same call types across individuals) vocal individuality technique for this species. Call-independent techniques were beyond the scope of this study but may be more appropriate. I also provide preliminary evaluation of the photo-identification technique for identifying individual palm cockatoos. Using up-close facial profile photographs of a presumed 13 individuals, I illustrate and provide unique and descriptive terminology for various facial features (namely on the beak) of this species that can probably be used to identify individuals. Four presumed individuals were photographed over several days and appear to be re-identifiable using this technique. I encourage further work be done on developing the photo-ID technique for this species. -- provided by Candidate.