24Wildlife Conservation Plan for Seabirds

24 Wildlife Conservation Plan for Seabirds

Native wildlife

The influence of native species on the breeding success of seabirds should not be over-looked. Prior to the Macquarie Island Pest Eradication Project, it was believed that the population of Brown Skuas (Stercorarius antarcticus) on the island were being kept artificially high as a result of the availability of introduced rabbits as prey (Ross et al. 1996). Following the eradication of introduced rabbits, there was increased predation pressure by Brown Skua on native seabird colonies (i.e. prey switching from rabbits to seabirds).

Silver Gulls (Chroicocephalus novaehollandiae) can pose a threat to seabirds, particularly around tourist developments and human refuse (Smith 1991, 1992; Egan and Smith 1994). Kelp and Silver Gulls are known to raid tern colonies for eggs and young chicks and in large numbers have the ability to inflict a heavy toll on nesting seabirds (Serventy et al 1971; Ross et al. 1996). Increased abundance of gull species has been related to poor management of waste disposal (Coulson and Coulson 1983) and poor feed management at aquaculture facilities (Harrison 2010). Maintaining and improving good management practices at waste and aquaculture facilities may be important in reducing predation impacts to seabird colonies.

Long-nosed Fur Seals (Arctocephalus forsteri) are known to predate Little Penguins in South Australian and western Victoria. Numbers of fur seal are recovering from severe harvesting in the 1800s (Shaughnessy et al. 2015). The increasing trend in South Australia is likely to continue into the foreseeable future, primarily by expansion in colonies on Kangaroo Island and by establishment of new colonies (Shaughnessy et al. 2015). Long-nosed Fur Seals will eat Little Penguins whereas Australian Fur Seals (A. pusillus) do not (Hume et al. 2004, Page et al. 2005) and Australian Sea Lions do so very rarely (McIntosh et al. 2006). In studies of the occurrence of Little Penguin remains in scats and regurgitates of Long-nosed Fur Seal, the occurrence is around 30 per cent in South Australia and western Victoria (Bool et al. 2007, Page et al. 2005). Predation of Little Penguins by Long-nosed Fur Seals has been identified as a plausible cause of penguin decline in some colonies.

Fisheries interactions and by-catch

From time-to-time seabirds may interact with fishing boats that use certain fishing gears, particularly trawl, longline, purse seine and gillnet gear (Clay et al. 2019). Incidental mortality (bycatch) in fisheries remains one of the greatest threats to seabirds globally (Clay et al. 2019). Birds are attracted to fishing vessels as a source of food, particularly when bait, by-catch and fisheries waste and offal is being thrown back into the ocean.

An ‘interaction’ is any physical contact a person, boat or fishing gear has with a protected species that causes the animal stress, injury or death (AFMA 2019). Interactions with seabirds in trawl fisheries occur when birds foraging on discards or offal are injured or killed on collision with net monitoring and warp cables, dragged underwater and drowned when their wings become entangled around the warp, or become entangled in nets. Birds can also get caught on the hooks of longlines when the gear is being deployed or retrieved and the birds are chasing the bait.