Christmas Island - Local Sea-birds
Christmas Island is best known to most people as the destination for refugees and asylum seekers who are trying to get to Australia from Indonesia. Boat smugglers load their rickety boats with desperate human cargo and head for Christmas Island.Credit: Wikimedia
Christmas Island is an Australian territory and is 2,600 kilometres north-west of Perth, the capital of Western Australia, and only 360 kilometres south of Djakarta, capital of Indonesia. It has an area of 135 square kilometres. Christmas Island sits in the ocean like a rocky bastion. Apart from asylum seekers, Christmas Island is famous for its red crab migration when thousands of red crabs move between the tropical rainforest areas and the sea.
However, because of its isolation and relative minimal human disturbance, there are large numbers of flora and fauna species which are only found here. Some of the following sea-birds are endemic to Christmas Island although they may frequent other shores.
Abbott's booby has the scientific name of Papasula abbotti. It is the rarest of the boobies and is about 79cm long and weighs around 1.5kg. Its black and white plumage is quite distinctive. The tail is black and the long, slender wings black-topped. It has a gliding flight reminiscent of an albatross. Abbott's booby is unlikely to breed until it is eight years old and then only breeds successfully about every second year. The lifespan is around 40 years.
Abbott's booby now breeds only on Christmas Island although it once bred on other islands in the region. It is mainly seen in the waters around the island. A single egg is laid in a precarious nest in a rainforest tree. Although the egg is laid mainly in June or July, the chick's first flight is not made until December or January. Juveniles remain dependent on their parents for food for another month. Fish and squid are regurgitated for the chick.
A third of the booby's nesting sites were destroyed by phosphate mining in the 1960s and 70s. Destruction of the forest results in significant wind turbulence which affects the flight and breeding success of the bird. There is strong fidelity to previous nesting sites and this, together with the slow reproductive rate, has also had an impact on the birds. Abbott's boobies are listed as 'endangered' with about 3000 birds remaining and numbers decreasing. Threats to its existence include cyclones, loss of habitat, yellow crazy ants, over-fishing and marine pollution.
The Great frigatebird (Fregata minor) is large but lightly built. It reaches to 105 cm long and is mainly black. The female is larger than the male and has a white throat and breast while the male's shoulder feathers have a purple-green iridescence. The red throat sac of the male is distended during the breeding season. It nests in colonies in trees all around the island.
Christmas Island frigatebird
The Christmas Island frigatebird (Fregata andrewsi) is classed as 'critically endangered'. The binomial honours Charles William Andrews, a British palaeontologist.
The male of this species is mostly black except for a white belly patch and a pale bar on the upper wings. It is a big bird, 90 to 100cm in length with a forked tail. The male has a red gular (throat) pouch and long, dark grey, hooked bill. The female has a black head and throat, white collar, breast and belly, pink bill and red eye ring. The dramatic throat pouch is inflated by the males during the breeding season which extends from December to June. Nests are built in tall forest trees. This species does well if it raises one chick every two years.
The Christmas Island frigatebird does not walk or swim but almost continually flies, foraging for flying fish, squid and other marine prey driven to the surface by subsurface predators.
It also engages in aerial piracy of other birds and is adept at stealing whilst on the wing. The frigatebird has been tracked on a non-stop flight of 26 days during which it covered 4,000 km.
The introduced predator, the yellow crazy ant, has decimated some of the bird populations. Most recent surveys put the numbers of mature birds at between 2,400 and 4,800. About 2/3rds of nests are now in a single colony. This makes the species vulnerable to cyclone activity.Credit: Wikimedia
The Red-Footed Booby
The red-footed booby (Sula sula rubripes) (above) is locally common and the most numerous of the sea-birds. It differs from the rare Abbott's booby because of the white tail and red feet. It nests in colonies in the trees on the lower shore terraces.
It is the smallest of the boobies reaching about 70cm in length with a wingspan of up to a metre. The beak and throat pouch are pink and blue and the legs red.
The Brown Booby
The brown booby (Sula leucogaster plotus) is also common and Christmas Island has one of the largest populations of brown boobies in the world. The plumage is a chocolate brown with a white breast and powder blue beak and feet. It nests among the pinnacles and inland cliff edges.
The Brown (Common) Noddy
The brown (common) noddy (Anous stolidus) (above) is a small, tropical seabird with a length of perhaps 42cm. It has a worldwide distribution and nests on the cliffs overlooking the beaches. It also frequents shore terrace trees. It is a sooty brown with a bright white cap. The lower eyelid is also white and fades to grey on the nape of the neck.
The Silver Bosun or red-tailed tropicbird has the scientific name of Phaeton rubricauda westralis. It is a medium size elegant bird with black eye markings and long red tail streamers. They nest on the ground on cliff ledges or under coastal bushes. Groups of twenty or more indulge in spectacular aerial displays off the cliffs. It is believed that there could be 1400 breeding pairs. The adult is slender and mainly white. Length ranges from 71 to 80cm. The central tail feathers are very long, doubling the total length of the bird.
The Golden Bosun
The golden bosun (Phaeton lepturus fulvus) is unique to Christmas Island. It is a variety of the white-tailed Tropicbird and smaller than the silver bosun. The delicate-looking golden bosun has prominent black bars on the upper wing, a golden tinge to the plumage and golden tail streamers. It is often seen on an undulating flight path near Flying Fish Cove and over the rainforest canopy.
Christmas Island is making concerted efforts to help its endangered species survive.