Foraging Far from Home: Gps-Tracking of Mediterranean Storm-Petrels Hydrobates pelagicus melitensis Reveals Long-Distance Foraging Movements

Summary. Identifying important foraging areas is fundamental to detecting the demographic drivers of a species and ultimately to plan conservation measures. For some species, such as small pelagic seabirds, foraging grounds are difficult to locate and remain largely unknown. We used miniaturised GPS devices (∼0.95g) to study foraging movements of Mediterranean Storm-petrels Hydrobates pelagicus melitensis during the incubation period. A total of 43 individuals at Benidorm colony (southwestern Mediterranean Sea) were tracked during a single foraging trip. We first assessed potential negative effects of the tracking devices. We recorded 22 complete foraging trips and measured home-range, foraging areas and the degree of overlap among individuals. We used first passage time analyses (FPT) to differentiate foraging/resting from flying/travelling activities and to infer potential foraging areas. All tracked birds returned to the colony. On average, individual body weight slightly decreased after foraging trips, suggesting a small immediate negative effect of the device. Tracked birds had high breeding success (0.71). Foraging trips lasted between 1 and 4.5 days with the total distance travelled ranging between 303.14 and 1,726.53km. The visited areas covered the whole south-western part of the Mediterranean Sea. Tracked individuals shared more than 50% of their home-range areas. Foraging areas were located further from the colony than previously thought (from 240 to 469km away) on deep sea areas of the Alboran Sea and Cartagena Canyons. Further studies are needed to locate foraging grounds during other life-cycle periods and to evaluate repeatability yearly, in order to determine the important marine areas for the species.—Rotger, A., Sola, A., Tavecchia, G. & Sanz-Aguilar, A. (2021). Foraging far from home: GPS-tracking of Mediterranean Storm-petrels Hydrobates pelagicus melitensis reveals long-distance foraging movements. Ardeola, 68: 3-16.