A new algorithm for the identification of dives reveals the foraging ecology of a shallow-diving seabird using accelerometer data
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The identification of feeding events is crucial to our understanding of the foraging ecology of seabirds. Technology has made small devices, such as time-depth recorders (TDRs) and accelerometers available. However, TDRs might not be sensitive enough to identify shallow dives, whereas accelerometers might reveal more subtle behaviours at a smaller temporal scale. Due to the limitations of TDRs, the foraging ecology of many shallow-diving seabirds has been poorly investigated to date. We thus developed an algorithm to identify dive events in a shallow-diving seabird species, the Scopoli’s shearwater, using only accelerometer data. The accuracy in the identification of dives using either accelerometers or TDRs was compared. Furthermore, we tested if the foraging behaviour of shearwaters changed during different phases of reproduction and with foraging trip type. Data were collected in Linosa Island (35°51′33″N; 12°51′34″E) from 12 June to 8 September 2015 by deploying accelerometer data loggers on 60 Scopoli’s shearwaters. Four birds were also equipped with TDRs. TDRs recorded only 17.7% of the dives detected by the accelerometers using the algorithm. A total of 82.3% of dives identified by algorithm were too short or shallow to be detected by TDRs. Therefore, TDRs were not accurate enough to detect most of the dives in Scopoli’s shearwaters, which foraged mostly close to the sea surface. Our data showed that birds performed shorter foraging trips and dived more frequently in the early chick-rearing period compared with the late chick-rearing and incubation phases. Furthermore, parents dived more frequently during short foraging trips. Our results suggest that Scopoli’s shearwaters maximised their foraging effort (e.g. number of dives, short trips) during shorter foraging trips and during early chick-rearing.
KeywordsAccelerometer Data Dive Duration Short Trip Seabird Species Trip Length
We wish to thank all people who participated in the fieldwork: Lucie Michel, Paolo Becciu, Enrica Martorelli, Katrin Quiring, Wiebke Schaefer, and Giulia Bambini. Thanks to Giacomo Dell’Omo for field work logistic. The project was supported by Ornis italica, Deutsche Forschungsgemeinschaft (PQ 148/8 and PQ 148/17), and the LIFE11 + NAT/IT/000093 ‘Pelagic Birds’.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Consent was obtained from all participants of the study. All animals were sampled and/or treated according to the national legislation. The study was conducted under a permit issued by the Regione Siciliana and Assessorato Risorse Agricole e Alimentari.
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