Hawaiian Forest Research Articles

Research and management priorities for Hawaiian forest birds

ABSTRACT Hawai‘i's forest birds face a number of conservation challenges that, if unaddressed, will likely lead to the extinction of multiple species in the coming decades. Threats include habitat loss, invasive plants, non-native predators, and introduced diseases. Climate change is predicted to increase the geographic extent and intensity of these threats, adding urgency to implementation of tractable conservation strategies. We present a set of actionable research and management approaches, identified by conservation practitioners in Hawai'i, that will be critical for the conservation of Hawaiian forest birds in the coming years. We also summarize recent progress on these conservation priorities. The threats facing Hawai‘i's forest birds are not unique to Hawai‘i, and successful conservation strategies developed in Hawai‘i can serve as a model for other imperiled communities around the world, especially on islands.

Estimating Cost-Effectiveness of Hawaiian Dry Forest Restoration Using Spatial Changes in Water Yield and Landscape Flammability Under Climate Change

Abstract: Resource managers increasingly seek to implement cost-effective watershed restoration plans for multiple ecosystem service benefits. Using locally adapted ecosystem service tools and historical management costs, we quantified spatially explicit management costs and benefits (in terms of groundwater recharge and landscape flammability) to assist a state agency in evaluating cobenefits for a predefined restoration scenario (focused on biodiversity benefits) and to prioritize an expanded restoration scenario in the state-managed Pu‘u Wa‘awa‘a watershed ( Hawai‘i) now and under the Representative Concentration Pathway (RCP) 8.5 midcentury climate scenario. Restoring all available areas increases recharge by ∼1.74 million m3/yr (5% of recharge over the entire watershed) under the current climate and does not meaningfully change recharge under RCP 8.5 midcentury, whereas climate change decreases recharge by ∼50%. For landscape flammability, climate change increases the median and maximum probability o...

Assessing the potential of translocating vulnerable forest birds by searching for novel and enduring climatic ranges.

Hawaiian forest birds are imperiled, with fewer than half the original >40 species remaining extant. Recent studies document ongoing rapid population decline and project complete climate‐based range losses for the critically endangered Kaua'i endemics ‘akeke’e (Loxops caeruleirostris) and ‘akikiki (Oreomystis bairdi) by end‐of‐century due to projected warming. Climate change facilitates the upward expansion of avian malaria into native high elevation forests where disease was historically absent. While intensified conservation efforts attempt to safeguard these species and their habitats, the magnitude of potential loss and the urgency of this situation require all conservation options to be seriously considered. One option for Kaua’i endemics is translocation to islands with higher elevation habitats. We explored the feasibility of interisland translocation by projecting baseline and future climate‐based ranges of ‘akeke’e and ‘akikiki across the Hawaiian archipelago. For islands where compatible climates for these species were projected to endure through end‐of‐century, an additional climatic niche overlap analysis compares the spatial overlap between Kaua’i endemics and current native species on prospective destination islands. Suitable climate‐based ranges exist on Maui and Hawai'i for these Kaua'i endemics that offer climatically distinct areas compared to niche distributions of destination island endemics. While we recognize that any decision to translocate birds will include assessing numerous additional social, political, and biological factors, our focus on locations of enduring and ecologically compatible climate‐based ranges represents the first step to evaluate this potential conservation option. Our approach considering baseline and future distributions of species with climatic niche overlap metrics to identify undesirable range overlap provides a method that can be utilized for other climate‐vulnerable species with disjointed compatible environments beyond their native range.

Rapid colonization of a Hawaiian restoration forest by a diverse avian community

AbstractDeforestation of tropical forests has led to widespread loss and extirpation of forest bird species around the world, including the Hawaiian Islands which have experienced a dramatic loss of forests over the last 200–800 years. Given the important role birds play in forest ecosystem functions via seed dispersal and pollination, a bird community's response to forest restoration is an important measure of the success of such conservation actions. We evaluated the bird response to reforestation at an important bird sanctuary, Hakalau Forest National Wildlife Refuge, Hawai′i Island, using 26 years of bird count data. We show that most species from within the diverse avian community increased significantly, but species colonized the restoration forest at different rates. Distance from intact forest and time since restoration were both important predictors of colonization rate, interacting such that for most species it took more time to colonize areas farther from the intact forest. In addition, both forest cover and understory diversity helped to explain bird densities, but the effect varied among species, suggesting that different habitat requirements may help drive variation in colonization rates. This article provides the first detailed evaluation of how a diverse community of birds has responded to one of the largest, ongoing reforestation projects in Hawai′i.

Methods for Measuring Bird-Mediated Seed Rain: Insights from a Hawaiian Mesic Forest 1

Amount and diversity of bird-dispersed seed rain play important roles in determining forest composition, yet neither is easy to quantify. The complex ecological processes that influence seed movement make the best approach highly context specific. Although recent advances in seed rain theory emphasize quantifying source-specific seed shadows, many ecological questions can be addressed u sing a less mechanistic approach that requires fewer assumptions. Using seed rain rates from 0.38 m2 hoop traps sampled twice monthly over the course of a year, we show that number of traps required to identify changes in seed rain varies across seed species and forest type. Detecting a 50% increase in amount of seed rain required from 65 to 300 traps, while detecting a 200% increase generally required ≤50 traps. Trap size and ecological context dictate the number of seeds found in each trap, but the coefficient of variation (CV) across traps in a given ecological context can help inform future studies about number of traps needed to detect change. To better understand factors influencing variation around estimates of seed rain, we simulated both clustered and evenly distributed patterns of fecal deposition using three different levels of seed aggregation (number of seeds in each fecal deposit). When patterns of fecal deposition were clustered, rather than evenly dispersed across the study area, they required 1.5 times the number of traps to identify a 100% increase in seed rain. Similarly, we found that low seed aggregation required 1.5 times the number of traps to detect a 100% change than when aggregation was medium or high. At low aggregations, fewer seed rain traps contained seeds (low, 33 ± 5%; medium, 23 ± 4%; high, 24 ± 5%), resulting in more variation across traps than medium and high aggregations. We also illustrate the importance of training observers to discern between morphologically similar seeds from different species and provide resources to help identify bird-dispersed seeds commonly found within midelevation mesic Hawaiian forests.

Birdsong meme diversity in a habitat landscape depends on landscape and species characteristics

Acoustic signaling is a form of information transmission that in many animal species may be behaviorally learnt and transmitted between individuals, creating flows of cultural traits (i.e. memes) across the landscape. The biogeography of memetic traits can have major implications for avian population evolution, ecology and conservation. We characterize the α (i.e. within population), β (i.e. among populations) and γ (i.e. total) acoustic diversity (i.e. number of memes) for four species of Hawaiian forest birds within a fragmented landscape. We study the effects of species characteristics (mobility and population size), and landscape variables (isolation and patch size) on patterns of meme diversity. We expect an increase in meme α‐diversity with patch and population size, and a decrease with patch isolation. We also expect β meme diversity to increase with patch isolation, and this relationship to be stronger for the less mobile species. We used spectrogram analyses and automatic sound recorders to characterize the acoustic diversity. We studied the overall meme structure and the factors affecting meme diversity with network analysis and a modeling approach. As predicted, large patches had richer α‐diversities for all species, while the effect of isolation was species‐dependent. Patches with larger populations showed greater α‐diversities for two species. β‐diversity only increased with distance for one highly mobile species. The structure of the acoustic traits was nested (i.e. memes in patches with lower meme diversities are a subset of the memes in patches with higher meme diversities) for all the species. Moreover, the meme structure for the ‘Apapane Himatione sanguinea suggested the existence of acoustic ‘dialects’. Meme diversity depended on both landscape variables (patch size and isolation), and some species characteristics (population size). The results of this study improve our understanding of the transmission of information by animals in fragmented landscapes.

Movements of four native Hawaiian birds across a naturally fragmented landscape

Animals often increase their fitness by moving across space in response to temporal variation in habitat quality and resource availability, and as a result of intra and inter‐specific interactions. The long‐term persistence of populations and even whole species depends on the collective patterns of individual movements, yet animal movements have been poorly studied at the landscape level. We quantified movement behavior within four native species of Hawaiian forest birds in a complex lava‐fragmented landscape: Hawai‛i ‘amakihi Chlorodrepanis virens, ‘oma‘o Myadestes obscurus, ‘apapane Himatione sanguinea, and ‘i‘iwi Drepanis coccinea. We evaluated the relative importance of six potential intrinsic and extrinsic drivers of movement behavior and patch fidelity: 1) forest fragment size, 2) the presence or absence of invasive rats (Rattus sp.), 3) season, 4) species, 5) age, and 6) sex. The study was conducted across a landscape of 34 forest fragments varying in size from 0.07 to 12.37 ha, of which 16 had rats removed using a treatment‐control design. We found the largest movements in the nectivorous ‘apapane and ‘i‘iwi, intermediate levels in the generalist Hawai‛i ‘amakihi, and shortest average movement for the ‘oma‘o, a frugivore. We found evidence for larger patch sizes increasing patch fidelity only in the ‘oma‘o, and an effect of rat‐removal increasing patch fidelity of Hawai‛i ‘amakihi only after two years of rat‐removal. Greater movement during the non‐breeding season was observed in all species, and season was an important factor in explaining higher patch fidelity in the breeding season for ‘apapane and ‘i‘iwi. Sex was important in explaining patch fidelity in ‘oma‘o only, with males showing higher patch fidelity. Our results provide new insights into how these native Hawaiian species will respond to a changing environment, including habitat fragmentation and changing distribution of threats from climate change.

Biotic and Abiotic Controls Over Canopy Function and Structure in Humid Hawaiian Forests

Foliar nitrogen (N) plays a key role in ecosystem function and dynamics, including processes such as photosynthesis, productivity, and decomposition. Aboveground carbon density (ACD Mg C ha−1) represents a cumulative functional outcome of these and other ecosystem processes and is an important metric for monitoring current carbon stocks. Despite their importance, multiple interacting controls over landscape-level variation in foliar N and ACD are poorly understood. We assessed the relative importance of individual ecologically important state factors (climate, substrate, age, vegetation, and topography) associated with canopy foliar N and ACD throughout a humid forest landscape. We combined high-resolution remotely sensed data, machine learning, and field data to map and assess canopy foliar N and ACD patterns across a 5016-ha forest reserve in Hawai‘i. Distance to non-native forests had the largest relative influence on canopy foliar N concentration, followed by mean annual temperature (MAT), vegetation type, precipitation, soil, canopy height, and substrate age. In contrast, soil type was the strongest determinant of spatial variability in ACD, followed by precipitation, MAT, and vegetation type. Similar to foliar N, climate and vegetation variables were associated with ACD. However, soil type was found to be much more important in the ACD model (30%) than in the foliar N model (4%). Landscape-scale patterns in canopy foliar N and ACD are the result of shifts in vegetation type and composition, most likely due to species’ responses to past disturbances, current climate conditions, and available nutrients. Degradation of native forests and future climate changes could result in highly altered biogeochemical cycles.

Landscape‐scale GPP and carbon density inform patterns and impacts of an invasive tree across wet forests of Hawaii

Plant invasion typically occurs within a landscape-scale framework of abiotic and biotic conditions, often resulting in emergent feedbacks among environment, ecosystem functions, and the dominance of invasive species. Understanding the mechanisms underlying successful invasions is an important component of conservation and management efforts, but this has been poorly investigated in a spatially explicit manner. Knowing where and why invasion patterns change throughout the landscape enables managers to use context-specific controls on the spread of invasive species. Using high-resolution airborne imaging spectroscopy, we studied plant performance in growth within and across landscapes to examine the dominance and spatial distribution of an invasive tree, Psidium cattleianum (strawberry guava), in heterogeneous environmental conditions of a submontane Hawaiian tropical forest. We assessed invader performance using the GPP ratio index, which is the relative difference in remotely sensed estimates of gross primary productivity between canopies of guava and canopies of the invaded plant community. In addition, we used airborne LiDAR data to evaluate the impacts of guava invasion on the forest aboveground carbon density in different environments. Structural equation modeling revealed that substrate type and elevation above sea level interact and amplify landscape-scale differences in productivity between the invasive species and the host plant community (GPP ratio); differences that ultimately control levels of dominance of guava. We found shifts in patterns of forest carbon storage based on both gradual increase of invader dominance and changes in environmental conditions. Overall, our results demonstrate that the remotely sensed index defined as the GPP ratio provided an innovative spatially explicit approach to track and predict the success of invasive plants based in their canopy productivity, particularly within a landscape-scale framework of varying environmental factors such as soils and elevation. This approach may help managers accurately predict where invaders of forests, scrublands, or grasslands are likely to exhibit high levels of dominance before the environment is fully invaded.

Prioritizing landscapes for restoration based on spatial patterns of ecosystem controls and plant–plant interactions

Summary The widespread degradation of natural ecosystems requires cost‐efficient restoration techniques that minimize risk and consider context‐specific restoration conditions. However, meeting these demands can be difficult because information on ecosystem‐level factors controlling vegetation and continuous spatial data on species interactions are often lacking. Using airborne light detection and ranging (LiDAR) data from a Hawaiian dry forest, we delineated crowns and assessed the 3D structure of more than 700 000 shrubs and trees. We used Random Forest machine learning to assess the relative importance of resource availability, environmental conditions, and disturbance regimes on canopy density. We then modelled and scaled up plant–plant interactions (i.e. potential nursery effects) to landscape units using a LiDAR‐derived Canopy Coalescence (CC) index. We used the relative importance of ecosystem factors, canopy cover, and CC index to prioritize landscapes for restoration. Here, we demonstrate a methodological framework that prioritizes landscapes in need of restoration (i.e. planting woody species) using two ecological perspectives: (i) ecosystem‐level controls on remnant woody vegetation, and (ii) potential interactions between established canopies and seedlings (e.g. nursery effect, competition). Our results highlight the heterogeneous nature of ecosystem‐level drivers affecting forest structure along elevation gradients. Consequently, the degree of potential nursery interactions between established canopies and seedlings at the landscape‐scale was context‐specific. Synthesis and applications. Our study provides a methodological approach that prioritizes landscapes for restoration by identifying the main controls on tree spatial distribution and by inferring the favourable conditions for seedlings. This approach can guide land managers to define cost‐efficient restoration strategies for large ecological areas.

Impact of nonnative feral pig removal on soil structure and nutrient availability in Hawaiian tropical montane wet forests

Conservation and restoration of ecosystems impacted by nonnative ungulates increasingly involves their removal and exclusion. While the influence of nonnative ungulate removal on plant communities is commonly monitored, impacts on underlying ecological processes are seldom quantified. Here we examined how nonnative feral pig (Sus scrofa) removal from Hawaiian tropical montane wet forests affects soil physical and chemical properties. Unique to this study, measurements were taken in paired sites inside and outside of five feral pig removal units representing a ~20 year, highly constrained chronosequence where other potentially confounding variables are held constant. Additional targeted measurements were taken inside and outside of a single exclosure in areas characterized by ‘low’ versus ‘high’ feral pig activity. Overall, nonnative feral pig removal increased stable soil aggregates and porosity, and decreased bulk density, water-filled pore space, and soil moisture content. Further, feral pig removal increased soil nutrient regeneration as evidenced by increased extractable cations, increased resin available NO3 − and total inorganic N, and enriched foliar δ15N. Increasing time since feral pig removal was positively related to net nitrification and total net inorganic N mineralization, and negatively related to pH and net ammonification. Results from both the chronosequence and targeted sampling were consistent in direction and support a central role of feral pig removal in modifying soil physical and chemical properties. Changes in soil properties following ungulate removal coincided with large increases in understory vegetation cover, highlighting the need to better understand aboveground-belowground linkages following nonnative ungulate removal.

Mitigating Future Avian Malaria Threats to Hawaiian Forest Birds from Climate Change.

Avian malaria, transmitted by Culex quinquefasciatus mosquitoes in the Hawaiian Islands, has been a primary contributor to population range limitations, declines, and extinctions for many endemic Hawaiian honeycreepers. Avian malaria is strongly influenced by climate; therefore, predicted future changes are expected to expand transmission into higher elevations and intensify and lengthen existing transmission periods at lower elevations, leading to further population declines and potential extinction of highly susceptible honeycreepers in mid- and high-elevation forests. Based on future climate changes and resulting malaria risk, we evaluated the viability of alternative conservation strategies to preserve endemic Hawaiian birds at mid and high elevations through the 21st century. We linked an epidemiological model with three alternative climatic projections from the Coupled Model Intercomparison Project to predict future malaria risk and bird population dynamics for the coming century. Based on climate change predictions, proposed strategies included mosquito population suppression using modified males, release of genetically modified refractory mosquitoes, competition from other introduced mosquitoes that are not competent vectors, evolved malaria-tolerance in native honeycreepers, feral pig control to reduce mosquito larval habitats, and predator control to improve bird demographics. Transmission rates of malaria are predicted to be higher than currently observed and are likely to have larger impacts in high-elevation forests where current low rates of transmission create a refuge for highly-susceptible birds. As a result, several current and proposed conservation strategies will be insufficient to maintain existing forest bird populations. We concluded that mitigating malaria transmission at high elevations should be a primary conservation goal. Conservation strategies that maintain highly susceptible species like Iiwi (Drepanis coccinea) will likely benefit other threatened and endangered Hawai’i species, especially in high-elevation forests. Our results showed that mosquito control strategies offer potential long-term benefits to high elevation Hawaiian honeycreepers. However, combined strategies will likely be needed to preserve endemic birds at mid elevations. Given the delay required to research, develop, evaluate, and improve several of these currently untested conservation strategies we suggest that planning should begin expeditiously.

Effects of long-term rainfall decline on the structure and functioning of Hawaiian forests

Climate change is altering the dynamics of terrestrial vegetation, with consequences for the functioning of Earth’s biomes and the provisioning of ecosystem services. Changes in forest dynamics due to drought events or short-term drying trends have been described at different ecological scales, but few observational studies have determined the relative effects of short- and long-term precipitation trends (e.g. decade and century, respectively) on forest canopy structure and functioning. Using gridded annual precipitation maps from 1920 to 2012, and temporal data from airborne light detection and ranging (LiDAR) and MODIS Enhanced Vegetation Index (EVI), we present evidence for a large-scale decline in forest canopy volume (area vs. height) and greenness (a metric of photosynthetic function) driven by a long-term drying trend on Hawaii island. Decreases in canopy greenness were observed in step with shorter-term (10 y) precipitation declines, but decreases in greenness were two-fold greater where longer-term (∼100 y) precipitation declines had occurred. Canopy volume mainly reduced where long-term precipitation declines occurred. We conclude that long-term precipitation trends critically impact forest canopy structure and functioning, which likely has cascading consequences for numerous ecological processes such as subcanopy light availability, species interactions, carbon storage, and animal habitat.

Daily survival rate of nests is lower in fruiting than non-fruiting tree species for a Hawaiian forest bird, the Kaua̒i ̒elepaio (Chasiempis sclateri)

ABSTRACT Nest-site characteristics are important drivers of nest success in birds, and are particularly important to understand in systems where anthropogenic factors may exacerbate their negative effects on population demographics. In Hawaii, it is suggested that forest bird nests in fruiting tree species may have higher rates of nest predation than in non-fruiting tree species, because fruit is an important dietary component of introduced rats. I assessed the differential daily survival rate (DSR) of nests of Kauai Elepaio (Chasiempis sclateri) on Kauai Island, Hawaii, in fruiting versus non-fruiting tree species using generalized linear models in program MARK. Nests were located in six fruiting tree species (n = 19) and one non-fruiting species (n = 25). Nest-tree reproductive strategy was a driver of DSR (β = −1.15 ± 0.55 SE, 95% CI = −2.23–-0.07) and DSR was lower in fruiting tree species compared to the non-fruiting species (0.975 vs. 0.992, respectively). Most nest failures were attributed to ...

Soil and hydrological responses to wild pig (Sus scofa) exclusion from native and strawberry guava (Psidium cattleianum)-invaded tropical montane wet forests

The structure and function of many ecosystems are threatened by non-native, invasive plant and animal species. Globally, invasive trees alter interception, evapotranspiration, water use, and throughfall, while wild pigs (Sus scofa) have been introduced and now invade widely ranging ecosystems, with impacts to soil and groundcover, and as a consequence, infiltration, runoff and water quality. In a resource management context, physical, chemical and biological control methods can limit the impact of plants on native biodiversity while fence building and animal removal can limit the effects of non-native ungulates on ecosystems. These expensive treatments have documented biodiversity benefits, but few studies have quantified hydrological effects of such management. Using paired fenced/unfenced runoff plots in native and Psidium cattleianum-invaded Hawaiian tropical montane forests, we examined the independent and interactive effects of strawberry guava (Psidium cattleianum), a highly invasive tree in tropical islands and wild pigs on runoff amount, soil erosion rates and fecal indicator bacteria (FIB). We sampled 18 events spanning a 22month period, and found that: 1) pigs are less active in invaded forests; 2) higher stem densities in invaded forests were associated with lower soil erosion and runoff rates compared to native forest; 3) reduced canopy cover and greater pig activity in native forests resulted in higher runoff volumes, soil erosion rates, and runoff FIB content; and 4) unfenced plots had more bare soil, less vegetation cover and greater soil FIB (Escherichia coli, total coliforms, enterococci) compared to fenced plots. These results point to the importance of understanding the independent and interactive effects of multiple invaders on watershed function. In this study system, removal of an invasive tree without fencing may actually lead to an increase in disturbance, with impacts to both biodiversity and hydrological properties.

Linking dominant Hawaiian tree species to understory development in recovering pastures via impacts on soils and litter

AbstractLarge areas of tropical forest have been cleared and planted with exotic grass species for use as cattle pasture. These often remain persistent grasslands after grazer removal, which is problematic for restoring native forest communities. It is often hoped that remnant and/or planted trees can jump‐start forest succession; however, there is little mechanistic information on how different canopy species affect community trajectories. To investigate this, I surveyed understory communities, exotic grass biomass, standing litter pools, and soil properties under two dominant canopy trees—Metrosideros polymorpha (‘ōhi‘a) and Acacia koa (koa)—in recovering Hawaiian forests. I then used structural equation models (SEMs) to elucidate direct and indirect effects of trees on native understory. Native understory communities developed under ‘ōhi‘a, which had larger standing litter pools, lower soil nitrogen, and lower exotic grass biomass than koa. This pattern was variable, potentially due to historical site differences and/or distance to intact forest. Koa, in contrast, showed little understory development. Instead, data suggest that increased soil nitrogen under koa leads to high grass biomass that stalls native recruitment. SEMs suggested that indirect effects of trees via litter and soils were as or more important than direct effects for determining native cover. It is suggested that diverse plantings which incorporate species that have high carbon to nitrogen ratios may help ameliorate the negative indirect effects of koa on natural understory regeneration.

Density‐dependent seedling mortality varies with light availability and species abundance in wet and dry Hawaiian forests

Summary Conspecific density may contribute to patterns of species assembly through negative density dependence (NDD) as predicted by the Janzen‐Connell hypothesis, or through facilitation (positive density dependence; PDD). Conspecific density effects are expected to be more negative in darker and wetter environments due to higher pathogen abundance and more positive in stressful, especially dry, environments (stress‐gradient hypothesis). For NDD to contribute to maintaining diversity, it should be apparent at the community‐wide scale as a negative correlation between seedling recruitment, growth or survival and conspecific adult abundance (community compensatory trend; CCT). We examined seedling survival in relation to con‐ and heterospecific adults within 10 m and con‐ and heterospecific seedlings within 1 m for 13 species within two 4‐ha permanent plots located in dry and wet forests in Hawaii. We also examined interactions between conspecific density and light and species’ commonness. For all species pooled, adult conspecific effects were positive (PDD) in both dry and wet forests, though they were stronger in the dry forest. In contrast, seedling conspecific effects were negative (NDD), though only significantly so in the wet forest. The strength and direction of density effects varied with understorey light such that seedlings had the highest survival where both adult conspecific density and light were high but the lowest survival where seedling conspecific density and light were high. In the wet forest, the most common species showed positive effects of adult conspecifics, but the less common species showed negative adult conspecific effects. We found mixed evidence for a CCT: seedling survival was positively correlated with basal area, but negatively correlated with tree density (stems ha−1). Thus, it remains unclear whether NDD is a diversity‐maintaining mechanism in these forests. Synthesis. Overall, we found that positive conspecific effects influenced seedling mortality patterns more than negative interactions did, even in tropical wet forest where NDD is predicted to drive species’ abundances. Additionally, the strength and direction of density effects varied with forest type, PAR, and species’ abundance, underscoring the need to consider abiotic factors and species’ life‐history traits in tests of density dependence hypotheses.

Quandaries of a decade‐long restoration experiment trying to reduce invasive species: beat them, join them, give up, or start over?

We evaluate the outcomes and consequences of a decade‐long restoration project in a Hawaiian lowland wet forest as they relate to long‐term management actions. Our initial study was designed both to promote native biodiversity and to develop knowledge that would enable land management agencies to restore invaded forests. Our premise of success followed the prevalent perception that short‐term management, such as removal of invasive species, ideally translates into long‐term and sustainable restoration. We were therefore disappointed and perhaps discouraged in our results—little recovery of native biodiversity despite ongoing and labor‐intensive management. Not only did we fail to return the invaded forest to a native‐dominated system but also our efforts lead to recruitment of new non‐native species assemblages. The sobering truth of many restoration projects in Hawaii and elsewhere is that we can never completely walk away and “consider the job finished,” or we have to accept that some ecosystems cannot be returned to an all‐native state. Essentially, costs of restoration may outweigh the accomplishment. This setback gave us an opportunity to reconsider and modify our initial approach. By starting over with a new direction using both native and non‐invasive but non‐native species, we have adopted a new philosophy of “join them.” In our revision, we changed the players in the game by following invasive species removal with outplantings of native and non‐invasive non‐native species that will functionally fill missing roles in the ecosystem. We link social interest in the new experiment to changing attitudes about naturalness.

Local prevalence and transmission of avian malaria in the Alakai Plateau of Kauai, Hawaii, U.S.A.

Avian malaria is among the most important threats to native Hawaiian forest birds. It is caused by the parasite Plasmodium relictum and is transmitted by the introduced mosquito vector Culex quinquefasciatus. Temperature increases and precipitation declines due to climate change over the last decade may be responsible for the observed recent expansion in the range and prevalence of avian malaria on the Alakai Plateau, Kauai Island. To examine the hypothesis that conditions are now favorable for transmission of malaria on the Plateau, mosquitoes were sampled with CO2 and Reiter oviposition traps at three sites (Kawaikoi, Halepa'akai, and Koke'e) on several occasions between October, 2013 and April, 2014. P. relictum infection was assessed by PCR or dissection under a microscope. We also surveyed mosquito larvae along Halepa'akai and Kawaikoi streams. We observed that Cx. quinquefasciatus is well established on the Alakai Plateau, as mosquitoes were caught on all field trips, except in April at Halepa'akai, and larvae were found throughout the year. We observed differences in adult abundance among sites and microhabitats (stream vs ridge lines).

Comparative demographics of a Hawaiian forest bird community

Estimates of demographic parameters such as survival and reproductive success are critical for guiding management efforts focused on species of conservation concern. Unfortunately, reliable demographic parameters are difficult to obtain for any species, but especially for rare or endangered species. Here we derived estimates of adult survival and recruitment in a community of Hawaiian forest birds, including eight native species (of which three are endangered) and two introduced species at Hakalau Forest National Wildlife Refuge, Hawaiʻi. Integrated population models (IPM) were used to link mark–recapture data (1994–1999) with long‐term population surveys (1987–2008). To our knowledge, this is the first time that IPM have been used to characterize demographic parameters of a whole avian community, and provides important insights into the life history strategies of the community. The demographic data were used to test two hypotheses: 1) arthropod specialists, such as the ‘Akiapōlā‘au Hemignathus munroi, are ‘slower’ species characterized by a greater relative contribution of adult survival to population growth, i.e. lower fecundity and increased adult survival; and 2) a species’ susceptibility to environmental change, as reflected by its conservation status, can be predicted by its life history traits. We found that all species were characterized by a similar population growth rate around one, independently of conservation status, origin (native vs non‐native), feeding guild, or life history strategy (as measured by ‘slowness’), which suggested that the community had reached an equilibrium. However, such stable dynamics were achieved differently across feeding guilds, as demonstrated by a significant increase of adult survival and a significant decrease of recruitment along a gradient of increased insectivory, in support of hypothesis 1. Supporting our second hypothesis, we found that slower species were more vulnerable species at the global scale than faster ones. The possible causes and conservation implications of these patterns are discussed.