North Island (Houtman Abrolhos)

The earliest recorded sighting of North Island occurred in May 1840, during the third survey voyage of HMS Beagle, commanded by John Clements Wickham. It was sighted from the peak of Flag Hill on East Wallabi Island in early May, explored on 22 May, and given its name due to "its relative position to the remainder of Houtman's Abrolhos". Before he left the island, Wickham left a letter in a bottle atop the highest hill, which he accordingly christened Record Hill.[2]

A map of the island first appeared in 1845 on a British Admiralty chart entitled "The Houtman Rocks". The following year, Wickham's lieutenant, John Lort Stokes, published the first account of the island in his Discoveries in Australia. He observed:[2]

"The island was about a mile across, and nearly circular. It was surrounded by a range of hills, with a flat in the centre, covered with coarse grass, where a great many quails were flushed, affording good sport, but not a single wallaby."

A western rock lobster fishery developed on the island in the early 20th century. There are records of the island being used as a base for crayfishers as early as 1902,[3] and for many years it was used as an anchorage by anglers. It was not until 1947, however, that a seasonally inhabited permanent camp was established there. According to former crayfisher Ron Bertelsen, the first camp was established by skippers George Barker and George Nelson and deckhand John Long, who relocated there when lobsters around Pigeon Island grew scarce. They camped at the southern end of North Island in a camp initially built from packing case timbers. A local carrier boat, the Betty Margaret, serviced the camp.[4] From about 40 seasonal inhabitants in 1940,[5] the population grew to about 130 by 2003. An airstrip was built in 1979.[6]

A number of naturalists have visited the island, starting with the Percy Sladen Trust Expedition to the Abrolhos Islands in 1913. This expedition spent little time on North Island, as shore collecting was not very successful there, and other islands appeared better suited to their work. Expedition members nevertheless published substantial information about the island, including a description of its physiography[7] and a list of its vertebrates.[8]

Australian ornithologist Dom Serventy visited the island in 1945 but left no published account. In 1959, a group from the University of Western Australia's Department of Zoology, accompanied by the English botanist Mary Gillham, travelled to the island; a brief article on its physiography, vegetation and vertebrate fauna was published the following year by Glen Storr.[5] More recent visitors have included P. R. Howden in 1974, Robert Ivan Taylor Prince in 1976, Ronald Eric Johnstone in 1981 and 1983,[9] Phillip Fuller in 1992,[10] and Judith Harvey and Vanda Longman in 1999.[11]

A tammar wallaby on North Island

No land mammals are known to be native to North Island, but the Australian sea lion (Neophoca cinerea) occasionally hauls out on the island's beaches, and it has been suggested that the island once had a native population of tammar wallaby (Macropus eugenii).

Stokes explicitly stated the tammar wallaby to be absent from North Island in 1840,[2] and it was not recorded by the Percy Sladen Trust Expedition in 1913. It was apparently introduced to the island in the 1920s, as early fishermen reported seeing it between 1928 and 1930. This introduction failed, possibly due to overgrazing.[6] The species was not found by Serventy during his 1945 visit, nor by Storr in 1959, but the latter found plenty of remains, mostly mandibles. Storr interpreted these remains as predating the 1920s introduction, suggesting that a native population of tammars became extinct on the island before 1840.[5] Albert Russell Main agreed,[22] but the theory has not been accepted by later researchers.[6][23]

Much of North Island has been heavily overgrazed by tammar wallabies. Note the difference in vegetation density either side of the fence line.

In 1985, five tammar wallabies were introduced onto North Island, and the population established successfully. Possible reasons for this success include the absence of the wallabies' natural predator, the carpet python (Morelia spilota imbricata);[24] the availability of additional food and water from the fishers' huts, which are occupied during the harshest time of the year; and the presence of the air strip, which apparently provides additional food for them.[6] By the 2000s, there were over 450 tammar wallabies on the island.[25] The wallabies overgrazed and ringbarked the native vegetation, particularly the area burnt in 1935,[6] thus reducing vegetation cover and causing a serious decline in populations of some plant species. In 2003, island residents asked the Department of Conservation and Land Management (CALM; now the Department of Environment and Conservation) for help in managing the issue. CALM staff visited the island in April and May of that year and produced a report recommending an investigation into controlling population levels by the use of implanted contraceptives.[6] Exploration of this option began in 2005,[24] but in July 2007 the research was discontinued. Around 60 wallabies were removed to educational institutions for research purposes, and culling began.[26] By February 2008, the wallaby population had been reduced to around 25 individuals.[25]

The only other mammal known to occur on the island is the naturalised house mouse (Mus Musculus).[23] Eight European rabbits (Oryctolagus cuniculus) were introduced in 1934, and were found to be "exceedingly numerous" by 1945, but by 1960 they were extinct, apparently from predation by feral cats.[5] Neither rabbits nor cats are now reported as naturalised on the island.[23]

Reptiles recorded on North Island include Binoe's prickly gecko (Heteronotia binoei), the gecko Christinus marmoratus, the Jew lizard (Pogona barbata), King's skink (Egernia kingii), the western limestone ctenotus (Ctenotus australis), the western worm lerista (Lerista praepedita),[5] the common dwarf skink (Menetia greyii),[27] and the Abrolhos bearded dragon (Pogona minor minima).[28] The carpet python was reported as present on the island in very low numbers before 1960, but it has never been observed there by naturalists,[5] and is now absent.[24]

The green turtle (Chelonia mydas) has been observed in large numbers near the shore, and it has been claimed that they breed on the island,[5] but this has never been verified.[29] If it is true, then North Island would be the species' most southerly breeding site in Western Australia.[5]

The birds most often mentioned in relation to North Island are the Abrolhos painted buttonquail (Turnix varius scintillans), a rare subspecies of the widespread painted buttonquail (Turnix varius) known only from the Wallabi Group and protected under the Wildlife Conservation Act 1950; and the brush bronzewing (Phaps elegans), one of the most common birds on North Island, the mainland populations of which are decreasing.[21]

Other birds known to breed on North Island include the osprey (Pandion haliaetus cristatus), greater crested tern (Thalasseus bergii),[21] Caspian tern (Hydroprogne caspia), silver gull (Chroicocephalus novaehollandiae novaehollandiae), and welcome swallow (Hirunda neoxena). Birds commonly recorded as resident on the island but not recorded as breeding there include the Pacific reef heron (Egretta sacra), white-bellied sea eagle (Haliaeetus leucogaster), red-capped plover (Charadrius ruficapillus), fairy tern (Sterna nereis nereis), Australian pipit (Antus australis) and western silvereye (Zosterops lateralis chloronotus). The sooty oystercatcher (Haematopus fuliginosus fuliginosus) and white-backed swallow (Cheramoeca leucosterna) have also rarely been observed as resident on the island.[9]

The most common visitors to the island are the bar-tailed godwit (Limosa lapponica baueri), grey-tailed tattler (Tringa brevipes), ruddy turnstone (Arenaria interpres interpres), red-necked stint (Calidris ruficollis) and curlew sandpiper (Calidris ferruginea). Other observed visitors include the great cormorant (Phalacrocorax carbo novaehollandiae), nankeen kestrel (Falco cenchroides cenchroides), banded lapwing (Vanellus tricolor), greater sand plover (Charadrius leschenaultii), whimbrel (Numenius phaeopus variegatus), greenshank (Tringa nebularia), sanderling (Calidris alba), willie wagtail (Rhipidura leucophrys leucophrys) and brown songlark (Cincloramphus cruralis).[9]

North Island is part of the Houtman Abrolhos Important Bird Area, identified as such by BirdLife International because of its importance for supporting large numbers of breeding seabirds.[30]

North Island's primary human use is as a seasonal camp for Western Rock Lobster fishers. During lobster season, which runs from 15 March to 30 June,[31] North Island's camp is occupied by about 130 fishers.[6] The camp is serviced by a carrier boat, the North Islander, which visits the island every three days, bringing supplies and taking out the catch and any domestic waste.[32]

North Island is considered to have high conservation value with respect to its populations of brush bronzewing and Abrolhos painted buttonquail, and its dune, limestone and salt lake vegetation communities. The potential existence of historically significant artefacts on Record Hill, namely the bottle left by Wickham and Stokes in 1840, has not been assessed.[21]

A 514 ha (1,270 acres) area of reef immediately south of North Island is designated a Reef Observation Area (ROA). Fishing is prohibited in this area, except for the use of lobster pots. One of four ROAs in the Houtman Abrolhos, these protected areas are intended to help conserve species of territorial fish that are fished elsewhere, and to provide divers with the opportunity to observe large populations that are not frightened by their approach.[33]

With extensive sand beaches, seabird breeding areas, and good dive sites in the Reef Observation Area to the south of the island, North Island is considered an attractive tourist site. However, all of the island's limited anchorage and jetty space is occupied by commercial fishers, so landings from private or charter boats are possible only by prior arrangement.[33] Moreover, visitors are not permitted to camp on the island.[34] North Island accounts for about 3.5% of private recreational boat trips to the Houtman Abrolhos and about 1% of commercial charter boat trips.[35] The most recent tourism plan for the Houtman Abrolhos supports the continued use of North Island by private charter boats and the use of the airstrip for tourism purposes, but recommends against the establishment of a land-based tourist site there.[33]