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Tropical, Oceanic, Majestic Seabirds… Frigatebirds

By Keith Hutton on August 31, 2016 in Other

Photo: Ian Montgomery

Photo: Ian Montgomery

Frigatebirds are spectacular, majestic and impressive birds, three species of which breed in Australian territory. Of these, Christmas Island Frigatebirds are more or less restricted to Christmas Island, as their name suggests. However, both Lesser and Great Frigatebirds are more widespread. In early June this year, during inclement weather, Lesser Frigatebirds were seen in the Eastern Suburbs at Maroubra despite their preference for the tropics, and at the same time both species were recorded as vagrants in Victoria and Tasmania.

Frigatebirds are among the easiest birds to identify. They are medium to large seabirds, predominantly black in colour, with long hooked bills and long tails. A diagnostic deep fork is obvious when their tails are spread. Adult females are bigger than males, with variable amounts of white on their underparts, and adult males have distinctive red throat pouches that they inflate during colonial breeding displays to attract females. Their wings are long and pointed, and they are able to remain in the air for long periods, soaring high and buoyantly with no apparent effort. Lesser Frigatebirds are much smaller than the others, the wingspans of which approach those of small albatrosses.

Adults are generally sedentary in Queensland and the Northern Territory. However, they may disperse great distances after breeding there. Young birds and males travel thousands of kilometres, soar for days on wind currents, and rarely if ever settle on the ocean; they roost and rest in trees or bushes when these are available. Both Lesser and Great Frigatebirds regularly turn up south of the tropics, and may be seen infrequently offshore in southern states as a consequence of tropical cyclones and winter storms.

Frigatebirds are opportunistic predators in sea bird colonies, but usually forage up to 500km from land, where they feed mainly on flying fish and squid out in the open sea. They grab eggs and downy young seabirds off the ground, take flying fish in the air, and catch squid by dipping or picking them off the water surface. Sometimes they hover when hunting, and they may also harass flying birds, chasing them and forcing them to disgorge their prey, then snatching the food before it hits the water, following dramatic flights of surprising speed and agility. They often associate with other feeding seabirds, dolphins and tuna, and usually hunt during the day, except if they have young to feed, when they hunt at night too.

The world population of Christmas Island Frigatebirds has always been small and they are critically endangered. On the contrary, the world populations of Lesser and Great Frigatebirds are both very large, but thought to be decreasing. Nevertheless, these two frigatebirds are regarded as being of least conservation concern at present. In their traditional distribution areas in tropical Australia Lesser Frigatebirds remain reasonably common, but Great Frigatebirds are not generally so numerous.