Did the animal move? A cross-wavelet approach to geolocation data reveals year-round whereabouts of a resident seabird.

Abstract

Background Considerable progress in our understanding of long-distance migration has been achieved thanks to the use of small lightweight geolocator devices. Such global location sensors (GLS) are particularly suitable for studying non-breeding movement and behaviour due to their small size and low energy consumption allowing multiyear deployment. Errors of geolocation are however important, difficult to estimate, have a complex structure leading to poor precision and accuracy. Therefore, understanding movement ecology of short-distance migrants or resident birds during extensive time periods remains challenging. We aimed at elucidating the sex-specific marine space uses of a resident tropical seabird, the masked booby over the full annual life cycle, including the breeding and non-breeding periods. Methods A total of 34 GLS were deployed on male and female masked boobies at the Fernando de Noronha archipelago (Brazil), and 31 of them were recovered and provided year-round data. Error range of geographical positions and habitat use of masked boobies were estimated from light-derived positions and temperature data. Synchronicity between movement and saltwater immersion data was investigated through a wavelet analysis. Results Masked boobies showed a resident behaviour over their entire annual cycle. We inferred from the wavelet analysis that birds traveled way and back from the colony on consecutive trips of short length (approx 2-4 days) and short range (approx 100-300 km) at the east of the colony. Trip duration and range depended on the sex of the individual and on the time of the year. Females had farther ranges than males during the pre-breeding period. Trip duration increased gradually from the end of the breeding period to the post-breeding period, probably due to the release of the central-place breeding constraints. Conclusions Despite inherent limits of light-based geolocation, synchronicity analysis of geolocation data revealed year round whereabouts of a resident tropical seabird and sex-specific movement behaviour. Such an approach based on the estimation of synchronicity between light-based coordinates data and any other external data (behavioural or environmental) could be used more broadly to investigate resident or short-migrants animal movement based on GLS data.