Kiritimati Totally Explained

Everything about Kiritimati totally explained

Kiritimati or Christmas Island is a Pacific Ocean atoll in the northern Line Islands and part of the Republic of Kiribati. The island has the greatest land area of any coral atoll in the world: about ; it's about in perimeter, while the lagoon shoreline extends for over . Kiritimati comprises over 70% of the total land area of Kiribati, a nation encompassing 33 Pacific atolls and islands. It lies north of the Equator, from Sydney, and from San Francisco.
Its roughly lagoon opens to the sea in the northwest; Burgle Channel (the entrance to the lagoon) is divided into the northern Cook Island Passage and the southern South Passage. The southeastern part of the lagoon is partially dried out today; essentially, progressing SE from Burgle Channel, the main lagoon gradually turns into a network of subsidiary lagoons, tidal flats, partially hypersaline brine ponds and salt pans, which as a whole has about the same area again as the main lagoon. Thus, the land and lagoon areas can only be given approximately, as no firm boundary exists between the main island body and the salt flats. – Kiribati's endemic reed-warbler, the Bokikokiko (Acrocephalus aequinoctialis). The 1957 attempt to introduce the Endangered Rimitara Lorikeet (Vini kuhlii) has by and large failed; a few birds seem to linger on, but the lack of abundant Coconut Palm forest, on which this tiny parrot depends, makes Kiritimati a suboptimal habitat for this species.

Flora

The natural vegetation on Kiritimati consists mostly of low shrubland and grassland. What little woodland exists is mainly open Coconut Palm (Cocos nucifera) plantation. There are three small woods of Pisonia grandis catchbird trees, at Southeast Point, Northwest Point, and on Motu Tabu. The latter was planted there in recent times. About 50 introduced plant species are found on Kiritimati; as most are plentiful around settlements, former military sites and roads, it seems that these only became established in the 20th century.) – important breeding colony; 8,000 birds before the 1982/83 decline, less than 3,000 in 1984 Charadriiformes

Micronesian Black Noddy (Anous minutus marcusi) – 20,000 birds before the 1982/83 decline

Little White Tern (Gygis microrhyncha) – 8,000 birds before the 1982/83 decline

Central Pacific Sooty Tern (Onychoprion fuscatus oahuensis) – among the very largest breeding colonies in the world; about 1,000,000 birds before the 1982/83 decline Pelecaniformes

Indopacific Lesser Frigatebird (Fregata ariel ariel) – important breeding colony; 9,000 birds before the 1982/83 decline

Central Pacific Great Frigatebird (Fregata minor palmerstoni it isn't clear whether even a severe curtailing of the cat population would be desirable. Though it previously was assumed that the small Polynesian Rat is of little if any harm for seabirds, even house mice have been shown to predate seabird nestlings. Most nesting birds, in particularly Procellariiformes, are now accepted to be jeopardized by Rattus exulans. The Kiritimati cats are meanwhile very fond of young seabirds; it even seems that their behavior has shifted accordingly, with cats being less territorial generally and congregating in numbers at active bird colonies, and generally eschewing to hunt rats when seabird chicks are in plenty. most of the relevant data remains classified to date however.
The 1982/83 "mega-El Niño" devastated seabird populations on Kiritimati. In some species, mortality rose to 90% and breeding success dropped to zero during that time. The biggest hazard caused by a changing climate would seem to be more prolonged and/or severe droughts, which could even enforce the island's abandonment as they did in 1905. However, it isn't clear how weather patterns would change, and it may be that precipitation increases.

Extinction

The type specimen of the Tuamotu Sandpiper (Prosobonia cancellata) was collected on Kiritimati in 1778, probably on January 1 or 2, during Captain Cook's visit. The expedition's naturalist William Anderson observed the bird, and it was painted by William Ellis (linked below). The single specimen was in Joseph Banks's collection at the end of the 18th century, but later was lost or destroyed. There is some taxonomic dispute regarding the Kiritimati population. As all Prosobonia seem(ed) to be resident birds unwilling to undertake long-distance migrations, an appropriate treatment would be to consider the extinct population the nominate subspecies, as Prosobonia cancellata cancellata or Kiritimati Sandpiper, distinct from the surviving Tuamotu Islands population more than 2,000 km (1,200 miles) to the southeast.
It may have been, but probably was not, limited to Kiritimati; while no remains have been found, little fieldwork has been conducted and judging from the Tuamotu Sandpiper's habits, almost all Line Islands would have offered suitable habitat. The Kiritimati population of P. cancellata disappeared in the earlier part of the 19th century or so, almost certainly due to predation by introduced mammals. While Prosobonia generally manage to hold their own against Polynesian Rats, they're highly vulnerable to the Black Rat and feral cats. Given the uncertainties surrounding the introduction date and maximum population of the former, the cats seem to be the main culprits in the Kiritimati Sandpiper's extinction. Given that the island was apparently settled to some extent in prehistoric times, it may already have lost bird species then. The geological data indicates that Kiritimati is quite old, was never underwater in the Holocene at least, and thus it might have once harbored highly distinct wetland birds. The limited overall habitat diversity on Kiritimati nonetheless limits the range of such hypothetical taxa, as does biogeography due to its remote location. At least one, possibly several Gallirallus and/or Porzana rails make the most likely candidates, given their former presence in the region and that conditions on Kiritimati would seem well suited. Perhaps a Todiramphus kingfisher was also present; such a bird would probably have belonged to the Sacred Kingfisher (T. sanctus) group as that species today occurs as a vagrant in Micronesia, and related forms are resident in SE Polynesia. These birds would have fallen victim to the Polynesian Rats and, in the case of the rails which would have almost certainly been flightless, hunting by natives.

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