The movement of a pelagic seabird: Defining movement techniques using the grey-faced petrel (Pterodroma macroptera gouldi)

Abstract

Movement is recognised as essential to the survival of animals and ecologists research movement patterns to better understand animal behaviour. The past two decades saw a rapid expansion of the movement discipline due to technological advances in global-positioning systems (GPS) and the availability of statistical methods for rapid analysis of the data obtained. These advances enable insights into precise movement paths of animals. I used GPS data-loggers to obtain high-resolution (30 second interval) movement trajectories of the grey-faced petrel (Pterodroma macroptera gouldi). The purpose was to describe a process for tracking and extracting behavioural information from seabird trajectories. This involved: (1) describing a technique for tagging petrels using GPS data-loggers; (2) discussing the foraging behaviour of breeding grey-faced petrels on Burgess Island; and (3) analysing the use of inferential movement models for defining behavioural states within individual trajectories. These results revealed that grey-faced petrels reach their foraging grounds via differing paths thus confirming that grey-faced petrels are comparable to other Procellariiformes in incorporating multiple strategies into their foraging behaviour. I also reaffirm the importance of the continental shelf region as a foraging ground for grey-faced petrels as was previously inferred based on prey analyses. I present a successful technique for obtaining and utilising GPS-tracking data. Inexpensive, modified data-loggers were successful for use on breeding grey-faced petrels during foraging trips. My thesis confirms that a computationally complex movement model more effectively defines biologically-probable behaviours from trajectories than alternative approaches. I also reveal that simplistic models can provide information regarding the presence or absence of behaviours such as ‘commuting’ thereby inferring the locations in which individuals are commuting compared to areas where they appear to focus their movements. The simplicity and accessibility of such a model has the potential to outweigh limitations of the output in some studies. Seabirds have the ability to inform conservation and climate change management plans due to their ability to track distributions of their pelagic prey. Therefore, techniques used and insights gained in this research have the potential to augment future conservation studies on petrels and could be utilised in crucially needed investigations of at-risk species.