130Wildlife Conservation Plan for Seabirds

130 Wildlife Conservation Plan for Seabirds

Grey Ternlet (Procelsterna cerulea)

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TABLE Species information for the Grey Ternlet

Grey Ternlet (Procelsterna cerulea) and Grey Noddy (P. albivitta) (del Hoyo and Collar 2014) were previously lumped as P. cerulea following Sibley and Monroe (1990, 1993). Cibois et al. (2016) found that Procelsterna sits within Anous, which is accepted and results in P. albivitta changing name to Grey Noddy Anous albivattus and P. cerulea changing name to Blue Noddy A. cerulea (del Hoyo et al. 2019). Grey Noddy breeds on Lord Howe and Norfolk Islands and on Kermadec Island, New Zealand. The species is a small delicate tern, with a slender black bill and moderately forked tail. Grey Noddies are distinctive with blue-grey above, grey-white head. The species is distributed across the Pacific Ocean and breeds on isolated tropical and subtropical islands, islets or rock stacks. Breeding can be continual in places and occurs in loose colonies (del Hoyo et al. 1996) but is poorly known. This species takes very small fish (average length 17 mm), squid, crustaceans and pelagic sea striders with proportions varying seasonally and geographically. It feeds on the wing by dipping or pattering.

The combined populations of Anous ceruleus and A. albivittus are estimated to number 27,000–120,000 individuals, but the total for A. albivittus is unknown. The global population trend is stable, although some populations have unknown trends (Delany and Scott 2006). Australian population estimates and trends are unknown.

Globally, the species is threatened by invasive species. Rodents on Lord Howe Island restrict breeding and rodent free islands have over 80 per cent breeding success (N. Carlile pers. comm). On Easter Island, the population is thought to be threatened by cat predation (Marin and Caceres 2010). It is possible that, in the future, the effects of climate change could have an adverse impact on food sources and breeding habitat.

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

Bridled Tern (Onychoprion anaethetus)

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TABLE Species information for the Bridled Tern

The Bridled Tern (Onychoprion anaethetus) is a medium-sized tropical tern, with a stout bill about the same length as head, long slender wings and a long deeply forked tail. The species is slightly smaller and slimmer than Sooty Tern (O. fuscata). The Bridled Tern breeds off the Pacific and Atlantic coast of Central America including the Caribbean, off small areas of western Africa, around Arabia and eastern Africa down to South Africa, off the coast of India, and in much of south-east Asia and Australasia excluding southern Australia and New Zealand (del Hoyo et al. 1996). It breeds on the periphery of vegetated coastal and continental (Haney et al. 1999) coral, rock or rubble islands and beaches (Higgins and Davies 1996, del Hoyo et al. 1996, Haney et al. 1999), volcanic stacks and exposed reefs (Haney et al. 1999). The nest is a scrape or depression in shingle or sand (Higgins and Davies 1996) that may be freshly excavated or re-used from a previous season (Higgins and Davies 1996). Nests are placed in a variety of concealed locations (Higgins and Davies 1996, del Hoyo et al. 1996). The species is not strictly colonial but solitary pairs usually congregate in suitable habitats (Haney et al. 1999) with neighbouring nests spaced according to nest-site availability (usually 1-5 m apart, minimum 30 cm) (del Hoyo et al. 1996). Most populations are migratory and dispersive and abandon their breeding sites at the end of the breeding season to overwinter at sea (Haney et al. 1999). Migratory movements have been documented from Houtman Abrolhos to the Celebes Sea, 3,800 km north (Surman et al. 2018) and some populations in the Indian Ocean seem entirely sedentary or only partially migratory (Haney et al. 1999). The timing of breeding varies geographically, most populations breeding annually in suitable habitat (Haney et al. 1999).