112Wildlife Conservation Plan for Seabirds

112 Wildlife Conservation Plan for Seabirds

Bycatch is a concern for all gannet species and Australasian Gannets interact with fisheries throughout their inshore foraging range with considerable potential for impacts from longline and set-net fisheries (del Hoyo et al. 2019). In New Zealand, Australasian Gannets have been assessed as being at relatively low risk from commercial fisheries with an estimated annual mortality of 62 individuals (95% confidence interval 7-222) (Richard and Abraham 2013). In New Zealand, the greatest mortality was observed in set-net fisheries (Richard and Abraham 2013).

Photograph of an Australasian Gannet diving for fish

Wildlife Conservation Plan for Seabirds 113

Masked Booby (Sula dactylatra)

TABLE Species information for the Masked Booby (Sula dactylatra)

The Masked Booby (Sula dactylatra) is the largest booby. It displays typical sulid characteristics of a streamlined body, long narrow wings, long neck, pointed bill and tail. Masked Boobies tend to be more solitary that Australasian Gannets (Morus serrator) sometimes in loose congregations, particularly when returning to breeding islands. This species ranges widely in tropical waters, being found in every ocean except the eastern Atlantic Ocean, northern Indian Ocean and the central-eastern Pacific Ocean (del Hoyo et al. 1992). Its breeding season depends on locality, forming small to medium-sized colonies of variable densities on rocky islands offshore. Nests are preferably built on cliff ledges, but a variety of other sites are used (del Hoyo et al. 1992). In Australia, breeding is largely confined to islands and cays in the Great Barrier Reef and Coral Sea Marine Park with other colonies occurring on Lord Howe and Norfolk Islands. Masked Boobies banded at Lord Howe Island have been found on two occasions on North East Herald Cay (Coral Sea Marine Park) suggesting that Lord Howe Island birds may regularly disperse into the Coral Sea before returning to breed at their natal colonies (Baker et al. 2008). Small colonies also occur on the islands of Ashmore Reef Marine Park, Lacepede, Bedout and Adele Islands, Western Australia. There is some conjecture on the subspecies of Masked Booby breeding within Ashmore Reef Marine Park. At sea, the species can normally be found over pelagic waters, preferring deeper waters than other boobies. It feeds on large species of shoaling fish, especially flying fish, but will also take large squid.

The global population size has not been quantified, but this species is described as 'fairly common' (Stotz et al. 1996). The population on the Lord Howe Island group, including Balls Pyramid was estimated in 2011 at 2,670 pairs (N. Carlile pers. comm). In the Coral Sea Marine Park, the largest colonies (>300 pairs) recorded were in the Cato Island and Saumarez Reef cays. The Australian population estimate and trends remain unknown.

Masked Boobies are sensitive to human disturbance, with visitors passing within 10-20 m causing birds to leave their nest (Borsa et al. 2010); however, this is not believed to be significantly affecting the population. Invasive species, primarily Black Rats Rattus rattus, also pose a threat in some parts of the booby's range, namely Clipperton Island, following the eradication of feral cats Felis catus (Pitman et al. 2005). Collection of eggs and hunting of adults from breeding colonies (del Hoyo et al. 2019) is thought to be causing slow and significant declines outside of Australia.