Abstract
BackgroundAmong the most widespread seabirds in the world, shearwaters of the genus Puffinus are also some of the deepest diving members of the Procellariiformes. Maximum diving depths are known for several Puffinus species, but dive depths or diving behaviour have never been recorded for great shearwaters (P. gravis), the largest member of this genus. This study reports the first high sampling rate (2 s) of depth and diving behaviour for Puffinus shearwaters.Methodology/Principal FindingsTime-depth recorders (TDRs) were deployed on two female great shearwaters nesting on Inaccessible Island in the South Atlantic Ocean, recording 10 consecutive days of diving activity. Remote sensing imagery and movement patterns of 8 males tracked by satellite telemetry over the same period were used to identify probable foraging areas used by TDR-equipped females. The deepest and longest dive was to 18.9 m and lasted 40 s, but most (>50%) dives were <2 m deep. Diving was most frequent near dawn and dusk, with <0.5% of dives occurring at night. The two individuals foraged in contrasting oceanographic conditions, one in cold (8 to 10°C) water of the Sub-Antarctic Front, likely 1000 km south of the breeding colony, and the other in warmer (10 to 16°C) water of the Sub-tropical Frontal Zone, at the same latitude as the colony, possibly on the Patagonian Shelf, 4000 km away. The cold water bird spent fewer days commuting, conducted four times as many dives as the warm water bird, dived deeper on average, and had a greater proportion of bottom time during dives.Conclusions/SignificanceGeneral patterns of diving activity were consistent with those of other shearwaters foraging in cold and warm water habitats. Great shearwaters are likely adapted to forage in a wide range of oceanographic conditions, foraging mostly with shallow dives but capable of deep diving.
Highlights
Shearwaters (Puffinus spp.) are among the most widespread seabirds throughout much of the world’s oceans, adapted for foot and wing-propelled diving [1,2,3], with several species undertaking trans-equatorial migrations [4,5]
We report the first deployments of Time-depth recorders (TDRs) on great shearwaters (P. gravis), sampling depth and temperature during foraging trips in the early incubation period
Tags were recovered from two birds after 17 d and 22 d foraging trips
Summary
Shearwaters (Puffinus spp.) are among the most widespread seabirds throughout much of the world’s oceans, adapted for foot and wing-propelled diving [1,2,3], with several species undertaking trans-equatorial migrations [4,5]. Many procellariiforms perform shallow (1–5 m) dives to capture prey [6,7], studies using depth recorders have revealed the relatively deep (.50 m) diving abilities of Puffinus shearwaters. These shearwaters exhibit maximum diving depths that are allometrically scaled and comparable in depth to those of penguins and alcids [2]. Maximum diving depths are known for several Puffinus species, but dive depths or diving behaviour have never been recorded for great shearwaters (P. gravis), the largest member of this genus. This study reports the first high sampling rate (2 s) of depth and diving behaviour for Puffinus shearwaters
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