150Wildlife Conservation Plan for Seabirds

150 Wildlife Conservation Plan for Seabirds

Pacific Gull (Larus pacificus)

TABLE Species information for the Pacific Gull (Larus pacificus)

The Pacific Gull (Larus pacificus) is the largest gull in Australia. The species is a powerful, deep-chested and thickset black-backed gull. At all times the species is easily identified by its deep massive bill, with prominent gonys and pear-shaped nostrils. It is bigger and bulkier than Kelp Gull (L. dominicanus). This species is endemic to Australia. The subspecies pacificus breeds in Tasmania, on many Bass Strait islands and westward along the Victorian coast from Wilson's Promontory to the South Australian border. The subspecies georgii is found on the coasts of south-western Western Australia and western South Australia. Its range has expanded in recent years northwards along the Western Australian coast (del Hoyo et al. 2019). Breeding occurs between September and January, either in small and open colonies or solitary (del Hoyo et al. 1996; Widdup 2013). Most nest sites are protected, however, by their inaccessibility, and the species has proved adaptable in exploiting new food sources provided by urbanisation (Garnett and Crowley 2000). It has a diverse diet including fish, squid, intertidal molluscs,

echinoderms and crabs, fish offal, carrion and refuse.

Delany and Scott (2006) estimate the population to be 11,000 individuals.

The population is suspected to be stable in the absence of evidence for any decreases or substantial threats (Wakefield et al. 2019). The Australian population estimate requires verification. Trends are unknown, however, increasing in south east Tasmania based on winter surveys 1980–2019 (E. Woehler pers. comm).

As with other coastal species, Pacific Gulls are prone to disturbance while breeding and feeding. Some populations have begun contracting (del Hoyo et al. 2019). Frequently observed at garbage facilities feeding. It is possible that, in the future, the effects of climate change could have an adverse impact on food sources and breeding habitat (Woehler et al. 2014).

Wildlife Conservation Plan for Seabirds 151

Kelp Gull (Larus dominicanus)

TABLE Species information for the Kelp Gull (Larus dominicanus)

The Kelp Gull (Larus dominicanus) is a large, black-backed gull similar in appearance to Pacific Gull (L. pacificus). The Kelp Gull breeds on coasts and islands through much of the Southern Hemisphere. It is found on a number of subantarctic islands, on the Antarctic Peninsula, on the southern coast of Australia and all of New Zealand, on the southern coast of Africa and Madagascar, and on the coast of South America as far north as Ecuador and southern Brazil (Basset et al. 1988; del Hoyo et al. 1996). It inhabits sheltered coastal harbours, bays, inlets, estuaries, beaches and rocky shores, usually foraging within 10 km of the shore but also following fishing boats beyond the continental shelf (Higgins and Davies 1996, del Hoyo et al. 1996). It may forage and roost in near-coastal inland habitats including lagoons, lakes, swampy basins, rivers, streams, reservoirs, pastures, cultivated land, tussock grassland, scrubland and cleared areas in pine plantations (Higgins and Davies 1996, del Hoyo et al. 1996, Hockey et al. 2005). Although this species is largely sedentary some southern populations migrate north after the breeding season (del Hoyo et al. 1996). The species breeds between late-September and January in colonies of up to several hundred pairs (occasionally nesting solitarily and remains gregarious outside of the breeding season (del Hoyo et al. 1996, Hockey et al. 2005).

The population is estimated to number 3,300,000–4,300,000 individuals

(BirdLife International 2019). The overall population trend is increasing, although some populations have unknown trends (Delany and Scott 2006). The Australian population estimate and trends are unknown. Presently increasing in south east Tasmania based on winter surveys 1980–2019 (E. Woehler pers. comm).

The Kelp Gull rapidly expanded its range in South Africa and in South America. The increased abundance is attributed to availability of food discards from trawlers and at fish processing factories and at waste disposal sites. In South Africa Kelp Gulls are aggressive predators of other seabirds on offshore islands. The species is potentially threatened by marine pollution (Parsons and Underhill 2005) and is susceptible to avian cholera (Hockey et al. 2005, Leotta et al. 2006) and avian botulism (Blaker 1967, Hockey et al. 2005) so may be threatened by future outbreaks of these diseases. The species also suffers mortality from interactions with trawler warp cables (Argentina) (Gonzalez-Zevallos et al. 2007). However, none of these threats are thought to pose a genuine threat to the population at present. Birds are frequently observed feeding at garbage facilities.