Tropical Wedge-tailed Shearwaters do not dive as deep as higher-latitude shearwaters

David Hyrenbach (Oceanic Institute, Hawai’i Pacific University, Waimanalo, Hawaii, USA) and colleagues report in ‘Elepaio (Journal of the Hawai‘i Audubon Society) on depths achieved by four diving Wedge-tailed Shearwaters Puffinus pacificus (WTSH) in Hawaii carrying tail/mounted time-depth-recorders (TDRs).  Maximum dive depth attained was 21.8 m.  Both single and multiple (bout) dives were recorded.

“[T]he mean maximum dive depths we recorded for WTSH are shallower than those of related sub-arctic, subtropical and tropical species [of shearwaters].  This result is consistent with anatomical evidence suggesting that WTSH are not deep divers, due to having significantly less laterally compressed tarsi than other diving species, like the Short-tailed Shearwater and the Sooty Shearwater.”

The paper concludes: “[f]uture research could further investigate the ecological context of night-time foraging and dive bouts.  To this end, we hypothesize that single dives and dive bouts indicate solitary foraging events and multi-species feeding flocks involving subsurface predators, respectively."

Wedge-tailed Shearwater, photograph by Alan Burger

Reference:

Hyrenbach, K.D., Gleichman, J.S. & Karnovsky, N.J. 2014.  Diving behavior of Wedge-tailed Shearwaters rearing chicks on Lehua Islet.  ‘Elepaio 74(4): 1-4.

John Cooper, ACAP Information Officer, 24 March 2014