text: north island ( houtman abrolhos ) north island is the northernmost island in the houtman abrolhos , a coral reef archipelago in the indian ocean off the coast of mid west western australia . located about 14 km ( 9 mi ) from the nearest island group , it is one of the largest islands in the houtman abrolhos , and one of the few to support dune systems . it has relatively diverse flora dominated by shrubs and fauna that includes the introduced tammar wallaby , around seven species of reptile , and about 15 resident bird species . first recorded and surveyed in 1840 , north island has been a seasonal camp for western rock lobster fishermen since the beginning of the 20th century , and this remains the principal focus of human activity on the island . there is also a small amount of tourism , though for the most part it is reserved as conservation habitat for vegetation communities and rare birds . history discovery 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 . 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 : " 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 . " development of industry and infrastructure 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 as early as 1902 , 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 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 . from about 40 seasonal inhabitants in 1940 , the population grew to about 130 by 2003 . an airstrip was built in 1979 . visits by naturalists 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 and a list of its vertebrates . australian ornithologist dom 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 , travelled to the island ; a brief article on its physiography , vegetation and vertebrate fauna was published the following year by glen storr . more recent visitors have included p. r. howden in 1974 , robert ivan taylor prince in 1976 , ronald eric johnstone in 1981 and 1983 , phillip fuller in 1992 , and judith harvey and vanda longman in 1999 . geography nominally located at 28 ° 18 ′ 9 ″ s 113 ° 35 ′ 41 ″ e , north island is an isolated island , separated from its nearest neighbours in the wallabi group by the 14 km ( 9 mi ) wide south passage . despite this separation , it is sometimes treated as part of that group . it is roughly diamond - shaped and is approximately 2 km ( 1 1 ⁄ 4 mi ) long from south to north , and 1 1 ⁄ 2 km ( 1 mi ) from west to east , giving it an area of about 180 hectares ( 450 ac ) . two high points are named record hill and latitude hill . these are the only gazetted places on the island , although some other features have informal names : the most northerly and southerly point on the island have been called " north point " and " south point " respectively , and in 1960 a high point in the northwest corner of the island was referred to as " northwest hill " . on the eastern side is a seasonally inhabited permanent fishers ' camp . there is an unnamed lighthouse on the western side , a trig point on the eastern side , and a gravel airstrip near the centre . the island is surrounded by a coral reef flat . this extends about 1 1 ⁄ 2 km ( 1 mi ) to the west of the island , and over 3 km ( 2 mi ) to the north and south , but the reef margin lies quite close to the island on the eastern side . most of the reef is not navigable , but a passage through the reef just north of the island is named suda bay passage ; one just south of the island is named barker passage ; and there are a few breaks or channels on the eastern side of the island where boats may obtain shelter in bad weather . an area of reef immediately north of the island is named the flat , and at the northern extreme of the reef is a breaker named the big breaker . about 200 m ( 660 ft ) west of the island is a small rock informally known as " shag rock " , but with no official name ; it differs from shag rock in the wallabi group further south . like the rest of the houtman abrolhos , north island is australian territory . it is a part of western australia , and falls within the boundaries of the federal electoral division of durack and the state electoral district of geraldton . it is part of the houtman abrolhos nature reserve , an a - class reserve managed by western australia 's department of fisheries . geology and physiography the basement of north island is the wallabi limestone , a dense , coral limestone platform that underlies the entire wallabi group . arising abruptly from a flat shelf , it is about 40 m ( 131 ft ) thick , and of quaternary origin . areas of reef that formed during the eemian interglacial ( about 125 , 000 years ago ) , when sea levels were higher than at present , are now emergent in places , and these form the basement of the group 's central platform islands , namely west wallabi island , east wallabi island and north island . north island 's basement for the most part does not exceed 1 . 5 m ( 4 ft 11 in ) in elevation . much of it is capped by , and nearly all of it is covered with sand , but there are some exposed outcrops . the southern margin of the island , for example , takes the form of a low cliff , which is severely undercut by the sea in many places . there are extensive dunes of unconsolidated holocene sand along both the western and eastern sides of the island . the topography of these dunes varies with time : in 1913 , dakin recorded the dunes as being a good deal higher in the east than in the west , but in 1960 storr found the eastern dunes to be severely eroded , apparently because of a fire that burnt much of the island 's vegetation in 1935 . in the centre of the island is a low plain with a sinkhole in its southwest corner and a small salt lake near its northern edge . the soil in the centre of the plain is shallow loam , whereas the rim is deeper and composed largely of shell fragments . climate an automatic weather station has been installed on the island since 1990 , and hourly measures of precipitation , air temperature , wind speed , wind direction , relative humidity and atmospheric pressure have been publicly available since then . this is the only weather station in the houtman abrolhos , so its data underlies climatic models of the island chain as a whole . based on the data for north island , the houtman abrolhos has been described as having a mediterranean climate with warm , dry summers and cooler , wet winters . mean temperatures range from 9 . 3 to 19 . 5 ° c ( 49 to 67 ° f ) in july , and from 19 . 1 to 32 . 4 ° c ( 66 to 90 ° f ) in february . this is a substantially smaller range than on the mainland : the summer temperature is typically a degree cooler , while winter temperatures are a good deal warmer . this is due to the influence of the ocean , in particular the leeuwin current . eighty - six percent of the island 's rain falls between april and september ; on average there are 89 rain days , resulting in 469 mm ( 18 in ) of rain . the wettest month is june , when over 100 mm ( 4 in ) typically falls . in contrast , only about 70 mm ( 3 in ) can be expected to fall between october and march . it is nearly always windy . during summer a high - pressure ridge lies to the south , causing persistent winds from the southeast or southwest at speeds exceeding 17 kn ( 31 km / h ) almost half the time . during autumn and winter , the ridge moves north , increasing atmospheric pressure over the islands and creating variable winds . winter tends to produce both the strongest gales and the most frequent periods of calm . in addition to these winds , there is daily pattern of land breezes in the morning , followed by the onset of south - westerly sea breezes in the afternoon . this pattern is caused by temperature differences between the land and the ocean ; it is not as strong in the houtman abrolhos chain as on the mainland , but is present . three classes of storm have been identified in the region . brief squalls may occur between december and april . a tropical cyclone occurs in the area about once in three years , between january and april ; these may generate extremely high wind speeds that are potentially destructive . during winter , extra - tropical cyclones sometimes pass south of geraldton , generating winter gales with gusts of up to 35 m / s ( 115 ft / s ) , the wind direction from the northwest initially , then gradually moving around to southerly . flora most of north island is dominated by shrubs , generally less than a metre ( 3 ft ) high . the beach vegetation is largely ( beach spinifex ) , salsola kali ( prickly saltwort ) , atriplex cinerea ( grey saltbush ) and naturalised maritima ( sea rocket ) . stable dunes are vegetated by atriplex paludosa ( marsh saltbush ) , scaevola crassifolia ( thick - leaved fan - flower ) , axillaris ( coastal daisy - bush ) , myoporum insulare ( blueberry tree ) and exocarpos ( broom ) . sheltered areas behind dunes support salsola kali and myoporum insulare and also ( nitre bush ) , the last of these being the only plant on the island to grow over 1 1 ⁄ 2 m ( 5 ft ) high . in areas where limestone is close to the surface , the vegetation consists of pimelea ( shrubby rice - flower ) , ( basket bush ) and preissii . the rim of the central plain is vegetated by a dense shrubland of baccata ( berry saltbush ) , atriplex paludosa and diffusa ( coast ) . nearer the centre , the vegetation consists of pauciflora ( ) , and tecticornia ( ) , although t. is replaced by tecticornia ( shrubby samphire ) where the soil is shallow . the most low - lying area of the central plain , south of the salt lake , is water - logged in winter ; it is vegetated by a dense mat of ( beaded samphire ) , sporobolus ( marine couch ) and australis ( ) . the dune , limestone and salt lake vegetation communities on north island are considered to have high conservation significance . the dune and limestone communities have high biodiversity , are highly sensitive to disturbance and regenerate slowly . the salt lake community is considered significant because of the rarity of salt lakes on offshore islands . according to a survey published in 2001 , the following vascular plants occur on north island : fauna mammals no land mammals are known to be native to north island , but the australian sea lion ( 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 , 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 . the species was not found by 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 . albert russell main agreed , but the theory has not been accepted by later researchers . 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 imbricata ) ; 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 . by the 2000s , there were over 450 tammar wallabies on the island . the wallabies overgrazed and the native vegetation , particularly the area burnt in 1935 , 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 . exploration of this option began in 2005 , but in july 2007 the research was discontinued . around 60 wallabies were removed to educational institutions for research purposes , and culling began . by february 2008 , the wallaby population had been reduced to around 25 individuals . the only other mammal known to occur on the island is the naturalised house mouse ( mus musculus ) . 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 . neither rabbits nor cats are now reported as naturalised on the island . reptiles reptiles recorded on north island include 's prickly gecko ( ) , the gecko marmoratus , the jew lizard ( barbata ) , king 's skink ( kingii ) , the western limestone ( australis ) , the western worm ( ) , the common dwarf skink ( ) , and the abrolhos bearded dragon ( minor minima ) . 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 , and is now absent . 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 , but this has never been verified . if it is true , then north island would be the species ' most southerly breeding site in western australia . birds the birds most often mentioned in relation to north island are the abrolhos painted buttonquail ( turnix varius ) , 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 ( elegans ) , one of the most common birds on north island , the mainland populations of which are decreasing . other birds known to breed on north island include the osprey ( pandion haliaetus cristatus ) , greater crested tern ( thalasseus bergii ) , caspian tern ( hydroprogne caspia ) , silver gull ( chroicocephalus novaehollandiae novaehollandiae ) , and welcome swallow ( ) . 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 ) , fairy tern ( sterna nereis nereis ) , australasian pipit ( australis ) and western silvereye ( zosterops lateralis ) . the sooty oystercatcher ( haematopus fuliginosus fuliginosus ) and white - backed swallow ( ) have also rarely been observed as resident on the island . the most common visitors to the island are the bar - tailed godwit ( limosa lapponica baueri ) , grey - tailed ( tringa brevipes ) , ruddy turnstone ( arenaria ) , red - necked stint ( calidris ruficollis ) and curlew sandpiper ( calidris ferruginea ) . other observed visitors include the great cormorant ( carbo novaehollandiae ) , kestrel ( falco ) , banded lapwing ( vanellus tricolor ) , greater sand plover ( charadrius ) , whimbrel ( numenius phaeopus variegatus ) , greenshank ( tringa ) , sanderling ( calidris alba ) , willie wagtail ( rhipidura leucophrys leucophrys ) and brown ( ) . 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 . human uses the entire houtman abrolhos is protected by an a - class nature reserve that is wholly vested in western australia 's minister for fisheries for purposes of " conservation of flora and fauna , tourism , and for purposes associated with the fishing industry " . fishing industry 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 , north island 's camp is occupied by about 130 fishers . 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 . conservation north island is considered to have high conservation value with respect to its populations of brush 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 . a 514 ha ( 1 , 270 acres ) area of reef immediately south of north island is designated a reef observation area ( ) . fishing is prohibited in this area , except for the use of lobster pots . one of four 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 . tourism 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 . moreover , visitors are not permitted to camp on the island . north island accounts for about 3 . 5 % of private recreational boat trips to the houtman abrolhos and about 1 % of commercial charter boat trips . 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 .