Small Oceanic Islands Research Articles

Making waves: Harnessing stormwater for resilient water supply - A blueprint for vulnerable continental coasts and oceanic islands

At the forefront of climate change and natural disasters, small islands like Puerto Rico confront immense challenges in sustaining an adaptive water supply. The challenges are further exacerbated when the islands’ constraints, such as geographic isolation, limited resources, aging infrastructure, constrained capacity, and environmental fragility, are compounded. As these issues increasingly impact low-lying continental coasts, home to approximately 40 % of the global population, similar water supply crises have already emerged or are anticipated in these regions. To surmount these widespread challenges, harnessing stormwater as a non-conventional water source presents a promising solution. A stormwater-enabled water supply system, collectively characterized by water source diversification, decentralization, and modularity, can enhance the resilience of water supply in these vulnerable regions, both in routine situations and during emergencies. This article identifies barriers to the implementation of stormwater-to-drinking water (STDW) practices in Puerto Rico and advocates for engineering solutions to utilize stormwater at both community and household scales in vulnerable continental coasts and small oceanic islands. The primary barriers in Puerto Rico include uncertainty in water quality, insufficient data on local stormwater availability and domestic water demand, economic constraints, and the lack of an adaptive power supply. To overcome these obstacles, we emphasize engineering strategies focused on modular system design, assessments of local stormwater capture and demand dynamics, advancements in treatment technologies, and the enhancement of energy resilience. By analyzing the Puerto Rican context, we propose a conceptual framework that outlines pathways to adaptive STDW strategies for other oceanic islands and larger, more complex continental coasts in the face of similar challenges. These pathways encompass enhancing system modularity, understanding the dynamics of local stormwater supply and water consumption, applying tailored treatment technologies, and strengthening the resilience of supporting infrastructures. The insights gained from Puerto Rico's experience can guide current and future efforts for resilient water supply solutions in increasingly vulnerable coastal, island, and other regions.

A Land Cover Change Detection Approach to Assess the Effectiveness of Conservation Projects: A Study Case on the EU-Funded LIFE Projects in São Miguel Island, Azores (2002–2021)

A Land Cover Change Detection Approach to Assess the Effectiveness of Conservation Projects: A Study Case on the EU-Funded LIFE Projects in São Miguel Island, Azores (2002–2021)

Population viability analysis predicts long‐term impacts of commercial Sooty Tern egg harvesting to a large breeding colony on a small oceanic island

The over‐exploitation of wild birds and the products derived from them can be a key threat driving changes in bird species richness and abundance. However, inadequate information on harvest levels combined with irregular population monitoring often means that the role of harvesting in population decline is difficult to quantify. Historically, the pan‐tropical Sooty Tern Onychoprion fuscatus has been subjected to extensive egg harvesting, yet the role of sustained harvesting in population change and future population viability remains unclear. In this study, we used published and new estimates of key demographic rates for a large, harvested Sooty Tern population in Seychelles, western Indian Ocean, to run a series of population viability analyses. We retrospectively assess the impact of historical levels of egg harvesting, and also predict how this population may respond under different future harvesting regimes, assuming no additional environmental change. We provide evidence that egg harvesting has played a substantial role in driving the population decline of Sooty Terns to date and demonstrate that continued harvesting will probably lead to further, possibly dramatic, declines in population size. These results indicate that recent levels of egg harvesting in Seychelles are not sustainable. We also show that the life‐history strategy of Sooty Terns, including a delayed age of first breeding, means the current 2‐year local moratorium on egg harvesting is unlikely to generate an observable population‐level response in Seychelles. Instead, we recommend that the current moratorium is extended at least beyond the age of first breeding (i.e. 5 years) to support appropriate evaluation. We additionally show that harvesting Sooty Tern eggs at much lower levels, i.e. 10% of the population size, is unlikely to reverse population decline. Therefore, long‐term egg harvesting strategies require careful evaluation to maintain a balance between the social, commercial, cultural and biodiversity significance of Sooty Terns in Seychelles.

Ecotype variation in the endemic tree Callicarpa subpubescens on small oceanic islands: genetic, phenotypic, and environmental insights.

Callicarpa subpubescens, endemic to the Ogasawara Islands, is suggested to have multiple ecotypes in the Hahajima Islands, specifically in the central part of the Ogasawara Islands. In this study, associations between genetic groups and spatial distribution, habitat, leaf morphology, size structure, and flowering time of each genetic group were investigated on Hahajima and the satellite Imoutojima Islands. Genetic groups were identified using EST-SSR markers, revealing four ecotypes named based on morphological features: Dwarf (D), Glabrescent (G), Tall (T), and Middle (M), with M being a result of the hybridization of G and T. Ecotype D, adapted to dry environments, is characterized by small tree size, dense thick leaves with abundant hairs, and is distributed in dry scrub. Ecotype G, adapted to understory of mesic forests, lacks leaf hairs. Ecotype T, adapted to the canopy of mesic forests, has hairy leaves and is tall in tree height. Ecotype M, adapted to the canopy of mesic scrub or edges of mesic forests, has hairy leaves but with a shorter tree height than ecotype T. Flowering peaks differed among all ecotype pairs except G and M, but the flowering times more or less overlapped among all ecotypes, suggesting that pre-mating isolation among ecotypes is not perfect. Post-mating isolation is considered absent, as there were no differences in the results, germination, and survival rates of one-year seedlings among inter- and intra-ecotype crossings. The existence of such ecotypes provides valuable insights into the ongoing speciation processes adapting to the oceanic island environments.

Seabird guano inputs increase impacts from introduced mammals on the native plants and animals of an oceanic island.

Seabirds create fluxes of nutrients from marine to terrestrial ecosystems that influence the food webs of small islands. We investigated how guano inputs shape terrestrial food webs by comparing species of selected plant and animal species in a red-footed booby colony in Mona Island (Puerto Rico, Caribbean Sea), to sites of the island lacking guano inputs. We quantified guano deposition and its relationship to plant biomass production, fecundity and density, as well as the activity of native and introduced animal species. In general, guano inputs increased the gross primary plant productivity, size, and fecundity by twofold. Guano inputs were also associated with twofold increases in density of Anole lizards, but also to increases in the activity of introduced pigs (> 500%), goats (> 30%), and cats (> 500%), which negatively impact native species. In particular, elevated pig and cat activity within the booby colony was correlated with lower activity of endemic ground lizards and of introduced rats. Our results also suggest that severe droughts associated with climate change exacerbate the negative effects that introduced species have on vegetation and reduce the positive effects of seabird guano inputs. Our findings underscore the importance of allochthonous guano inputs in subsidizing plant productivity and native and endemic species in small oceanic islands, but also in increasing the negative impacts of introduced mammals. Management and conservation efforts should focus on the exclusion (or eradication) of introduced mammals, particularly pigs and goats, from remnant seabird colonies in Mona Island.

Unraveling Island Economies through Organic Residue Analysis: The Case of Mocha Island (Southern Chile)

Abstract Biophysical conditions played a fundamental role in early human colonization of insular territories, particularly in food-producing societies dealing with limited resources and the challenges of maintaining a sustainable carrying capacity. Studies on past human colonization of small oceanic islands thus offer insights into economic plasticity, ecological impacts, and adaptation of early food-producing groups. On the coast of southern Chile, early evidence is dated to 950 cal BP of island colonization by coastal populations with mainland subsistence systems based on the exploitation of marine resources, along with gathering, managing, and cultivating plants and hunting terrestrial animals. Strikingly, the extent to which these mixed economies contributed to insular colonization efforts is largely unknown. Here we used organic residue analysis of ceramic artifacts to shed light on the subsistence of populations on Mocha Island in southern Chile. We extracted and analyzed lipids from 51 pottery sherds associated with the El Vergel cultural complex that flourished in southern Chile between 950 and 400 cal BP. Chemical and stable isotope analysis of the extracts identified a range of food products, including C3 and C4 plants and marine organisms. The results reveal the central role of mixed subsistence systems in fueling the colonization of Mocha Island.

Dependency on Mangroves Ecosystem Services is Modulated by Socioeconomic Drivers and Socio-Ecological Changes – Insights From a Small Oceanic island

Dependency on Mangroves Ecosystem Services is Modulated by Socioeconomic Drivers and Socio-Ecological Changes – Insights From a Small Oceanic island

Adaptive phenotypic and genomic divergence in the common chaffinch (Fringilla coelebs) following niche expansion within a small oceanic island.

According to models of ecological speciation, adaptation to adjacent, contrasting habitat types can lead to population divergence given strong enough environment-driven selection to counteract the homogenizing effect of gene flow. We tested this hypothesis in the common chaffinch (Fringilla coelebs) on the small island of La Palma, Canary Islands, where it occupies two markedly different habitats. Isotopic (δ13 C, δ15 N) analysis of feathers indicated that birds in the two habitats differed in ecosystem and/or diet, and analysis of phenotypic traits revealed significant differences in morphology and plumage colouration that are consistent with ecomorphological and ecogeographical predictions respectively. A genome-wide survey of single-nucleotide polymorphism revealed marked neutral structure that was consistent with geography and isolation by distance, suggesting low dispersal. In contrast, loci putatively under selection identified through genome-wide association and genotype-environment association analyses, revealed amarked adaptive divergence between birds in both habitats. Loci associated with phenotypic and environmental differences among habitats were distributed across the genome, as expected for polygenic traits involved in local adaptation. Our results suggest a strong role for habitat-driven local adaptation in population divergence in the chaffinches of La Palma, a process that appears to be facilitated by a strong reduction in effective dispersal distances despite the birds' high dispersal capacity.

Особенности формирования субфоссильных спорово-пыльцевых спектров острова Кетой (Центральные Курилы)

The composition and ratios of main components of pollen assemblages from the surface layer of peatlands, soils, lake sediments, and alluvial silts in different parts of the Ketoi Island were analyzed. The island, despite its small size, is distinguished by a complex organization of the landscapes. The pollen spectra represent well the local vegetation at the sampling sites, regardless of the genesis of sediments. Pollen brought from adjacent territories does not have a significant effect on the composition of pollen spectra. The spectra from soil deposits in the southeastern part of the island are represented by heather pollen; in the southwestern part, by tree pollen, mostly Siberian dwarf pine, alder, and birch pollen. Among nonarborescent pollen, Asteraceae and Ericaceae are dominant. The pollen spectra obtained from pioneer soil in the western part of the island consist of club moss spores (Lycopodium clavatum), which represent communities on overgrown rockfall deposits. The assemblages of the surface layer of peatlands contain large amounts of sedge and grass pollen. The pollen spectra from alluvial silts represent the vegetation of small valleys, where alder, dwarf pine, and Erman’s birch along the sides are common. The pollen spectra from the sediments of small lakes represent local biotic communities very well. Allochthonous pollen of dark coniferous and broad-leaved trees is present in the spectra in small quantities, except for two samples. This pollen was brought from the southern islands, including those of Japan. The data obtained can be used for paleogeographic reconstructions in the analysis of the formation of pollen spectra on small oceanic islands.

Trophic connectivity between the terrestrial and marine ecosystems of Malpelo Island, Colombia, evaluated through stable isotope analysis

The trophic dynamics of islands with low terrestrial primary productivity often depend on marine allochthonous inputs from nearby donor habitats. For instance, on Malpelo Island, Colombia (4° 00′ 05.63″ N; 81° 36′ 36.41″ W), the Nazca booby Sula granti affects the productivity and trophic dynamics of the terrestrial ecosystem by delivering nutrients, primary in the form guano, chick carcasses, and eggs. This study evaluated the trophic connectivity between the terrestrial and marine ecosystems of Malpelo Island, Colombia based on the isotopic (δ13C and δ15N) assessment of 403 samples (107 terrestrial and 296 marine) collected between 2017 and 2021. Isospaces were estimated based on δ13C and δ15N values, contribution of terrestrial sources in consumer diets (mixing model), 15 N enrichment in C3 plants, and interactions among environments (overlap). δ13C and δ15N values showed a larger terrestrial isospace (134.7‰2) than the marine isospace (117.2‰2). The mixing model indicated that detritusTerrestrial (median: 30.2%) contributed more to the food web than C3 plants (0.2%), reflecting high δ13CMarine content. The high isotopic overlap (> 60%) between terrestrial and marine isospaces suggests a significant trophic connection between environments. These results show the role of the marine ecosystem on the terrestrial ecosystem and the importance of S. granti regarding nutrient transfer between environments. The conservation of this seabird is essential to maintain the balance of this insular ecosystem. Using stable isotopes, this study was able to reveal trophic relationships between ecosystems associated with small oceanic islands that host large seabird colonies but have low primary productivity.

Spatial modelling and policy evaluation of the offshore wind potential for a small oceanic island: the case of Mauritius

Spatial modelling and policy evaluation of the offshore wind potential for a small oceanic island: the case of Mauritius

Public perceptions, knowledge, responsibilities, and behavior intentions on marine litter: Identifying profiles of small oceanic islands inhabitants

Marine litter is a global threat, particularly on oceanic islands where the problem is exacerbated. Perceptions, knowledge, awareness, and attitudes towards the theme are crucial in its mitigation and prevention. This study assessed these points through a questionnaire to the inhabitants of a Portuguese archipelago. Data revealed that people associate marine litter with plastic and its impacts and are well informed about its sources and pathways. Yet, the degradation rates of marine items were frequently underestimated and the problem of marine litter was attributed, among others, to littering, single-use products, and excessive packaging. Some individuals did not consider themselves responsible for reducing marine litter, attributing responsibilities to third parties. The youngest group, men, and students were the ones who reported less litter-reducing intentions and behaviors. Distinct profiles were traced using the questionnaire's answers, highlighting who needs marine litter literacy. Individuals who do not consider marine litter a current threat and live in a community that does not care about marine litter (profiles 1 and 2) were the groups that needed deeper intervention, due to their low perception and understanding of the problem. Marine litter literacy, management, and governance measures are necessary so that the public recognizes marine litter as a current threat, is worried about its impacts, avoids plastic use, and choses re-useable products (profile 4). In the studied oceanic islands, results indicated marine litter is not fully perceived by the public. A global and transformative shift in the way people are educated and behave towards waste and pollution is required, thereby highlighting the importance of increasing public perceptions assessment and marine litter literacy in the society.

Even short‐distance dispersal over a barrier can affect genetic differentiation in Gyraulus, an island freshwater snail

Abstract Dispersal is a fundamental mechanism for maintaining biodiversity, and long‐distance dispersal (LDD) has attracted the interest of many researchers owing to its unusual characteristics. Conventionally, LDD has been defined based on absolute and proportional distances; however, it has recently been redefined based on geographic and genetic limits. Based on this redefinition, short‐distance dispersal can have the same characteristics as LDD, depending upon the dispersal dynamics of an organism. However, the effects of LDD at a local scale on the genetic structure and diversification of organisms are poorly understood, since many studies have focused on definitive LDD, such as oversea dispersal. We focused on the freshwater snail Gyraulus sp. on an oceanic island, Chichijima Island, attempting to clarify the dynamics and effects of LDD on its genetic structure. We conducted molecular phylogenetic analyses, including divergence‐time estimation, using mitochondrial DNA and nuclear DNA markers to reveal the origin of the snail. In addition, we clarified the genetic structure, gene flow, and evolutionary history of snails on the island using mitochondrial DNA and genome‐wide single‐nucleotide polymorphisms. Finally, we followed a landscape ecology approach to identify barriers to dispersal. Our phylogenies suggested that the snail has a single origin. Based on our divergence–time estimation, colonisation was estimated to have occurred around the late Pliocene to early Pleistocene. Our population genetic analyses documented genetic differentiation even within this small oceanic island. Based on the divergence time estimation and approximate Bayesian computation using single‐nucleotide polymorphisms, the differentiation was estimated to have begun around the late Pleistocene. Little gene flow occurred between the geographically structured snail genetic groups. Landscape analysis suggested that catchment boundaries were a major barrier to dispersal. Considering the geography of the island, these results suggested that low‐frequency dispersal over barriers is an important factor in genetic differentiation within the island. Furthermore, dispersal over barrier may be considered LDD, even though the dispersal distance is only several kilometres. Genetic evidence also suggested that resistance to gene flow over the barrier, rather than distance, is more important in determining whether dispersal should be considered LDD. This suggests that a definition of LDD that depends only on the distance may mislead an understanding of dispersal mode.

Random mating and the lack of sex-biased kin clustering in an island population of the bull-headed shrike, Lanius bucephalus

The encounter with relatives at the time of mating can be reduced if one or both sexes breed away from the natal site, and it is often assumed that this occurs to a lesser extent on islands where only short dispersal is possible. However, endemic insular populations may have evolved fine-tuned dispersal patterns enabling effective avoidance of inbreeding even in a small habitat, and the influence of spatial constraint should be more apparent for non-endemic than endemic populations. Recently established island populations of originally migratory birds can provide insights into the direct effect of habitat area on inbreeding risk. We studied spatial distribution of kin and inbreeding in a population of the bull-headed shrike, Lanius bucephalus, that became established on small oceanic islands separated from the mainland by > 360 km, Minami-daito and Kita-daito Islands, early in the 1970s. Sex-specific spatial genetic structure that could reduce inbreeding risk was absent within the focal Minami-daito Island. This result remained unchanged after the neighbouring Kita-daito Island was incorporated into the analysis. Average relatedness of breeding pairs was not different from that expected under random mating, and FIS was no greater than zero. The estimates of extra-pair paternity frequency were not high (4.5–16% of offspring, depending on the estimation method) compared to the mainland. Inbreeding coefficient of offspring was variable among nests, indicating some occurrence of inbreeding. We found no clear evidence of recent population bottleneck, suggesting that the purging of deleterious recessive alleles did not occur upon colonisation. These results suggest the absence of obvious inbreeding avoidance despite the potentially negative effects of inbreeding. Future studies should quantify inbreeding depression and also formally rule out the possibility that inbreeding is not avoided as an adaptive strategy as has been suggested for endemic island species.

Impacts on food web properties of island invertebrate communities vary between different human land uses

Human land use is of growing concern for island ecosystems. Besides direct impacts on biodiversity, land uses can alter the functioning and structure of ecosystems. Central to this are impacts on food webs. The release of additional nutrients from human origin, habitat homogenization, or environmental filtering due to human land use can change the diet of individual consumer species (i.e., their trophic niches) and the distribution and overlap of trophic niches within a food web. However, it remains largely unclear whether the effects on food web properties vary between the different and predominant human land uses present on islands. Here, we investigated the impact of two dominant human land uses on small oceanic islands (i.e., urban and tourism development) and tested if and how different land uses on islands affect food web structure. To disentangle human land uses, we investigated islands, which were either privately owned by a tourist facility (i.e., exclusively tourism land use) or experienced urban development from the local population (i.e., urban land use), or remained uninhabited, serving as reference sites free of direct land use. Using stable isotope analysis, we show that isotope signature, trophic (isotopic) niches, and overall food web properties of the investigated island invertebrate communities were significantly changed under both land use regimes. While trophic diversity was reduced and trophic niche widths increased under tourism land use, the investigated food webs showed reduced trophic diversity at the food web base and a more uneven trophic niche distribution under urban land use. In summary, these findings show that different human land uses can have contrasting impacts on oceanic island food webs. As oceanic islands experience rapidly growing human land conversion, our results indicate that they may also face increasing yet unpredictable long-term changes in food web dynamics.

Strong horizontal and vertical connectivity in the coral Pocillopora verrucosa from Ludao, Taiwan, a small oceanic island.

Mesophotic habitats could be sheltered from natural and anthropogenic disturbances and act as reproductive refuges, providing propagules to replenish shallower populations. Molecular markers can be used as proxies evaluating the connectivity and inferring population structure and larval dispersal. This study characterizes population structure as well as horizontal and vertical genetic connectivity of the broadcasting coral Pocillopora verrucosa from Ludao, a small oceanic island off the eastern coast of Taiwan. We genotyped 75 P. verrucosa specimens from three sites (Gongguan, Dabaisha, and Guiwan) at three depth ranges (Shallow: 7–15 m, Mid-depth: 23–30 m, and Deep: 38–45 m), spanning shallow to upper mesophotic coral reefs, with eight microsatellite markers. F-statistics showed a moderate differentiation (FST = 0.106, p<0.05) between two adjacent locations (Dabaisha 23–30 and Dabaisha 38–45 m), but no differentiation elsewhere, suggesting high levels of connectivity among sites and depths. STRUCTURE analysis showed no genetic clustering among sites or depths, indicating that all Pocillopora individuals could be drawn from a single panmictic population. Simulations of recent migration assigned 30 individuals (40%) to a different location from where they were collected. Among them, 1/3 were assigned to deeper locations, 1/3 to shallower populations and 1/3 were assigned to the right depth but a different site. These results suggest high levels of vertical and horizontal connectivity, which could enhance the recovery of P. verrucosa following disturbances around Ludao, a feature that agrees with demographic studies portraying this species as an opportunistic scleractinian.

Tourism and urban development as drivers for invertebrate diversity loss on tropical islands.

Oceanic islands harbour a disproportionately high number of endemic and threatened species. Rapidly growing human populations and tourism are posing an increasing threat to island biota, yet the ecological consequences of these human land uses on small oceanic island systems have not been quantified. Here, we investigated and compared the impact of tourism and urban island development on ground-associated invertebrate biodiversity and habitat composition on oceanic islands. To disentangle tourism and urban land uses, we investigated Indo-Pacific atoll islands, which either exhibit only tourism or urban development, or remain uninhabited. Within the investigated system, we show that species richness, abundance and Shannon diversity of the investigated invertebrate community are significantly decreased under tourism and urban land use, relative to uninhabited islands. Remote-sensing-based spatial data suggest that habitat fragmentation and a reduction in vegetation density are having significant effects on biodiversity on urban islands, whereas land use/cover changes could not be linked to the documented biodiversity loss on tourist islands. This offers the first direct evidence for a major terrestrial invertebrate loss on remote oceanic atoll islands due to different human land uses with yet unforeseeable long-term consequences for the stability and resilience of oceanic island ecosystems.

Na Vuku Makawa ni Qoli: Indigenous Fishing Knowledge (IFK) in Fiji and the Pacific

The time-tested Indigenous fishing knowledge (IFK) of Fiji and the Pacific Islands is seriously threatened due to the commercialization of fishing, breakdown of traditional communal leadership and oral knowledge transmission systems, modern education, and the movement of the younger generations to urban areas for work and/or study. Consequently, IFK, which has been orally transmitted for generations, has either been lost, not learned by the current generation, or remains undocumented. This study focuses on the critical need to conserve and include IFK as a basis for assessing the conservation status of ecologically and culturally keystone fisheries species as a basis for planning site-specific management of marine and freshwater fisheries in Fiji and the Pacific Islands. The study reviews studies of the last two and a half centuries on IFK from Fiji and elsewhere in the small oceanic islands of the Pacific, as a basis for the conservation, documentation and intergenerational transfer of this knowledge as the foundation for sustainable fisheries management. The study also reviews: the nature and conservation status of IFK, itself; and the conservation status of species considered to be of particular ecological and cultural importance; reasons for the loss of species/taxa and associated knowledge and practices; and actions that can be taken to address this loss.

Multi-decadal coastal evolution of a North Atlantic shelf-edge vegetated sand island — Sable Island, Canada

Impacts from a changing climate, in particular sea-level rise, will be most acutely felt on small oceanic islands. A common configuration of mid-latitude islands is the sandy barrier island. Sable Island, Nova Scotia, Canada is a vegetated sand island near the shelf edge, 160 km from the nearest point of land, that is morphologically similar to a barrier island. This study uses 60 years of airphoto records to analyse changes in coastline position through digitized shore and vegetation (foredune proxy) lines. Rates of coastal movement are analysed to model the future (2039) coastal configuration. The analyses suggest that the majority of the coastline on Sable Island is in retreat, with net retreat on the south side of the island only partially offset by modest net advance on the north side. The different morphologies of the beach–dune systems of South Beach and North Beach, driven by incident wind and waves, yield these different coastline responses. Projected loss of 10 ha by 2039 of the climax heath vegetative community to shoreline retreat suggests a trend toward island instability due to coastline migration. Island-wide data set trends show support for two different but complementary hypotheses about whole-island evolution: (1) the island is mobile via bank migration driving southern coastline changes and experiencing sediment transport toward the east, or (2) the island is generally immobile and losing subaerial sediments (and thus shrinking) likely due to ongoing (and accelerating) sea-level rise.

Small‐scale species distribution model identifies restricted breeding habitat for an endemic island bird

AbstractMapped geographical distributions of many birds are an overestimation of their true range and this overestimation is particularly high for threatened species. Due to their restricted ranges, specialized habitats and inability to relocate to other areas, island birds are particularly vulnerable to anthropogenic effects on their habitats, but few studies have investigated the suitability of remaining habitat for species restricted to small oceanic islands. Here, we developed a fine‐scale species distribution model to investigate the breeding habitat of the Lord Howe currawong Strepera graculina crissalis. Using 73 nest locations as occurrence records, we found that currawongs nest preferentially near creek lines at lower elevations in the forested areas of the island (maximum elevation of 120 m). Habitat suitability decreased rapidly as the distance to creeks increased, indicating that many forested areas far from a creek line were unsuitable habitat for nesting currawongs. Using a combination of Thiessen polygons and suitable habitat to define territory boundaries, we estimated the average territory size to range between 2.48 ha and 5.23 ha. Using a conservative threshold, our model identified 195 ha of Lord Howe Island’s land area as highly suitable nesting habitat for the Lord Howe currawong, while using a less conservative threshold identified a further 246 ha as medium suitable habitat (441 ha total). Hence, we estimated that the island can support a maximum number of 84 breeding territories. This study shows that the Lord Howe currawong has a narrower ecological niche than was expected, lowering the carrying capacity for this species on the island. As birds on remote islands are often unable to relocate to other suitable areas, it is important to determine the remaining habitat to ensure the continued persistence and conservation of threatened island species.