110Wildlife Conservation Plan for Seabirds

110 Wildlife Conservation Plan for Seabirds

Great Frigatebird (Fregata minor)

Image unavailable in extracted textTABLE Species information for the Great Frigatebird

The Great Frigatebird (Fregata minor) is a very large black, or black and white seabird larger than most seabirds in the tropics. Major breeding populations are found in tropical waters of the Pacific and Indian Oceans. The Great Frigatebird breeds on small, remote tropical and sub-tropical islands, in mangroves or bushes and occasionally on bare ground (del Hoyo et al. 1992). The species has a protracted breeding cycle, averaging 16 months, to raise a single chick (Nelson 1976). Successful breeders from one year rarely if ever attempt to breed in the following year. Juveniles remain dependent until well into their second year, overlapping the subsequent nesting cycle (James and McAllan 2014). Fish, squid and chicks of other bird species (e.g. Sooty Terns) have all been identified as prey (Weimerskirch et al. 2004). It is frequently observed attempting to steal food from other bird species (Vickery and Brooke 1994). However, this behaviour represents a minor source of energy intake (Vickery and Brooke 1994; Weimerskirch et al. 2004).

The global population estimate is 500,000–1,000,000 individuals (BirdLife International 2019). Christmas Island provides breeding habitat for an estimated 3,500 pairs (James and McAllan 2014). Other important populations include those at North Keeling Island, the islands of Ashmore Reef Marine Park (50 pairs; Cannell and Surman 2020), Adele Island, WA and in several Coral Sea Marine Park islands and cays. Baker and Holdsworth (2013) reported that from a regional perspective, the Herald Cays (Coral Sea Marine Park) contain a significant proportion of the region’s breeding populations, particularly for the Great Frigatebird. As at 2012, there were 20-year and 10-year data sets available for North East Cay (Herald Cays) and South West Cay (Herald Cays), respectively. Over the 20-year period (1992-2012), the number of frigatebirds (Great and Lesser Frigatebirds) declined at an annual rate of 7.7 per cent.

Suspected increases in the frequency of ENSO (El Niño Southern Oscillation) events with climate change (Timmermann et al. 1999) may pose a threat to the survival and breeding success of Great Frigatebirds of unknown severity (Anderson 1989, Weimerskirch et al. 2010). Human disturbance has minor effects on the species; boats approaching the beach trigger flushing of nesting and roosting individuals (Borsa and Boiteux 2007 in Borsa et al. 2010).

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

Wildlife Conservation Plan for Seabirds 111

Australasian Gannet (Morus serrator)