Diving of Great Shearwaters (Puffinus gravis) in Cold and Warm Water Regions of the South Atlantic Ocean

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.

Functional relationship between group size and population density in Northwest Atlantic seabirds

“…GRSH is a shallow-diving species (Ronconi et al 2010) and is known to join flocks of conspecifics and other species (Haney et al 1992), which is compatible with the finding that this species occurred in large groups and quite often in the presence of other species. No saturating functional relationship was documented for this species during the winter surveys despite the fact that the range of population densities was quite large in comparison to other species in the data set.…”

First satellite tracks of the Endangered black-capped petrel

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Stage-dependent distribution of the Critically Endangered Amsterdam albatross in relation to Economic Exclusive Zones

“…Thiebot et al 2011). Nevertheless, chick-rearing adult Amsterdam albatrosses showed the greatest foraging radius of any breeding seabird so far, approaching a maximum distance of 4000 km from their colony (great shearwaters Puffinus gravis reached 3813 km, Ronconi et al 2010; white-chinned petrels Procellaria aequinoctialis reached 2420 km, Catard & Weimerskirch 1999;andwandering albatrosses 2618 km, Weimerskirch et al 1993). As found in the latter studies, these long-range trips measured here were part of a 2-fold foraging strategy typical of breeding Procellariiformes.…”