76Wildlife Conservation Plan for Seabirds

76 Wildlife Conservation Plan for Seabirds

 Maintain bycatch mitigation strategies in the ETBF

 Assess the impact of bycatch from gill-nets, purse-seines, longlines and inshore trawl across the range (Japan, Australia, Russia and New Zealand)

 Investigate potential impacts of the WA fisheries and apply appropriate mitigation techniques if required

 Determine non-breeding areas, migration routes and at sea distribution

 Implement best practice quarantine measures at breeding colonies to reduce the risk of any invasive species (re)establishing on islands

 Develop mitigation measure to reduce roadkill on Lord Howe Island

Photograph of a Flesh-footed Shearwater in flight over open ocean

Wildlife Conservation Plan for Seabirds 77

Sooty Shearwater (Ardenna grisea)

TABLE Species information for the Sooty Shearwater (Ardenna grisea)

The Sooty Shearwater (Ardenna grisea) is a large solid-bodied shearwater,

closely resembling the slightly smaller Short-tailed Shearwater (A. tenuirostris). Sooty Shearwaters are entirely dark brown-grey with a broad pale streak down the centre of the underwing. The species is abundant in the Southern Ocean during summer months, particularly around New Zealand. The species nests on islands and headlands in large colonies on islands off New Zealand, Australia and Chile, and the Falkland Islands (Islas Malvinas). In Australia, there are colonies on 17 islands, all of which contain fewer than 1,000 pairs. Burrows are dug under tussock grass, low scrub and on the Snares Islands under Olearia forest. Birds typically do not return to their natal colonies until the age of four years. They feed on fish, crustacea and cephalopods, which are caught while diving. Short (1-3 days) and long (5-15 days) provisioning trips are made by parents; longer trips allow foraging along the Antarctic Polar Front, reducing competition close to breeding grounds and allowing vast colonies to persist (Weimerskirch

1998). The species migrates to the Northern Hemisphere during the Austral winter (Shaffer et al. 2006, Hedd et al. 2012), and in the California Current, Sooty Shearwater numbers have decreased by 90 per cent in the last 20 years (Veit et al. 1996). It remains uncertain whether this has resulted from population decrease or distributional shifts (Spear and Ainley 1999), given there is no evidence from colonies of a decrease of 90 per cent.

The global population is estimated at 4.4 million pairs, roughly equating to 19–23.6 million individuals (Newman et al. 2009, Waugh et al. 2013). In southern Chile, some colonies number up to 200,000 pairs, with the largest colony of up to 4 million individuals on Isla Guafo (Reyes-Arriagada et al. 2007). In the Falklands (Islas Malvinas), 10,000-20,000 pairs have been recorded. New Zealand supports more than 180 colonies. In 1970-1971, the colonies on the Snares Islands were estimated to support 2,750,000 breeding pairs (del Hoyo et al. 1992, Heather and Robertson 1997).