Avian malaria is an existential threat to a majority of native Hawaiian forest birds. Climate change is facilitating the spread of malaria to historically disease‐free areas, and despite the risk of native Hawaiian forest bird extinctions from malaria outbreaks, no comprehensive disease management plans exist for forest bird conservation areas. Hakalau Forest National Wildlife Refuge, Hawai‘i, supports a thriving bird community in a historically disease‐free area that is now vulnerable to malaria incursion. Drawing on the expertise of land managers and research scientists, we developed an approach that could be used to proactively address the risk of expanding malaria into the Refuge. The plan lays out a multi‐level approach that includes options for monitoring and management actions depending on defined threat levels: Vigilant, High Alert, Disease Outbreak, and Crisis levels. Initial Vigilant and High Alert levels monitor bird populations, climate conditions, and mosquito occurrence for signs of possible disease outbreaks, with higher levels shifting toward more direct management responses. While specific actions will change as new tools become available, the proactive approach can help Refuge managers better respond to changing malaria levels in the future and provide a model for managing disease here in Hawai‘i and elsewhere.

Malaria parasites in the genus Plasmodium are ubiquitous infectious agents. Most avian species effectively manage infection and experience limited population effects, with a notable exception in the Hawaiian Islands. Since Hawaiian honeycreepers evolved over ~7 million years without blood parasites, the introduction of Plasmodium relictum had devastating consequences-including widespread extinctions and extirpations. However, honeycreeper species have been differentially affected by malaria. Using whole genome sequences for 35 O'ahu 'amakihi (Chlorodrepanis flava), we conducted a genome-wide association study to identify single nucleotide polymorphisms (SNPs) correlated with avian malaria infection. Infection status was determined using real-time PCR on blood samples. We identified 582 SNPs associated with malaria infection. Annotations included long ncRNAs, genes associated with transcription regulation, apoptosis, T-cell and complement activation, autophagosome assembly and transport, and intracellular calcium flux. By identifying genes regulating intracellular calcium ions, a key signaling molecule in Plasmodium replication, our work shows that host limitations on parasite replication may not solely depend on the adaptive immune response. Host responses can also involve restricting intracellular components essential for completion of parasite life cycles. This adds to a growing wildlife disease literature indicating a broad range of mechanisms of disease resistance rather than common pathways.

The Hawaiian honeycreepers, one of the world's most iconic adaptive radiations, are facing a human-mediated extinction crisis. More than 60 Hawaiian honeycreepers (Fringillidae: Carduelinae: Drepanidini) evolved from a single rosefinch-like ancestor that colonized the Hawaiian Islands. Only 17 Hawaiian honeycreeper taxa are known to be extant, of which only the common 'amakihi (Chlorodrepanis virens) and 'apapane (Himatione sanguinea) are classified as "Least Concern." Using mitogenome, whole-genome, and hybridization-capture data, we present a comprehensive phylogeny of the historically known Hawaiian honeycreeper radiation. We also place two taxa known only from paleontological specimens (Vangulifer neophasis and cf. Xestospiza conica) in their phylogenomic context. We demonstrate that most Hawaiian honeycreeper lineages diversified in a "Big Bang" of adaptive radiation correlating with the formation of O'ahu and that interspecies introgression likely played a role in this process. Using whole-genome data, we confirm putative interspecies admixture [N. A. S. Przelomska et al., Biol. Lett. 21, 20250265 (2025)] between the 'ō'ū (Psittirostra psittacea) and Lāna'i hookbill (Dysmorodrepanis munroi) and document ongoing gene flow across the 'amakihi species complex. Furthermore, we reject the synonymization of Vestiaria ('i'iwi) and Drepanis (Hawai'i and black mamo). Instead, the mamo species form an extinct clade with no close extant relatives, demonstrating a greater loss of phylogenomic diversity than previously understood.

Two aspects of host infectiousness shape pathogen transmission and distribution but are underappreciated: the relationship between pathogen load and infectiousness, and variability in pathogen load within species. We quantified the relationship between host pathogen load (parasitemia) for avian malaria (Plasmodium relictum) and infectiousness for biting Culex quinquefasciatus mosquitoes with experimental infections in canaries (Serinus canaria). Using this relationship, we estimated the infectiousness of 17 bird species in 11 communities in Hawai'i and quantified the relative contributions of infection stage (acute versus chronic) to transmission. We show that infectiousness to mosquitoes increased with parasitemia, temperature, and time since feeding. The relationship's gradual (low) parasitemia slope resulted in a wide range of parasitemias being partly infectious, and high within-host species variability in parasitemia led to extensive overlap in infectiousness among hosts. Disproportionate mosquito host utilization (inferred from relative infection prevalence) elevated the importance of a few host species, yet broad overlap in species infectiousness resulted in similar total infectiousness across most bird communities. This similarity likely contributed to avian malaria's widespread distribution throughout Hawai'i despite diverse host community assemblages. Our findings highlight the importance of both the shape of the pathogen load-infectiousness relationship and within-species variability in determining a pathogen's host range, transmission intensity, and spatial spread.

Native Hawaiian forest birds are experiencing an unprecedented extinction crisis. In particular, the iconic Hawaiian honeycreeper radiation has declined to just 17 out of ∼60 species remaining, most threatened with extinction due to avian malaria. Here, we investigate the genomic signatures of these declines in three honeycreeper species: the critically endangered 'akikiki (Oreomystis bairdi) and 'akeke'e (Loxops caeruleirostris) and the extinct po'ouli (Melamprosops phaeosoma). Surprisingly, we find that Hawaiian honeycreepers, even the last known po'ouli individual, maintain high heterozygosity compared with other island birds, reflecting historically large population sizes. This high heterozygosity may contribute to an elevated impact of inbreeding depression, as evidenced by reduced survival and reproductive success among highly inbred 'akikiki. Demographic analysis revealed that recent precipitous declines in 'akikiki and 'akeke'e coincide with the spread of avian malaria in the late 20th century, consistent with malaria being the primary driver of population collapse. Using predictive population viability modeling, we explore potential recovery scenarios for 'akeke'e, which has recently declined below 100 individuals in the wild. Our models predict that, under current conditions, 'akeke'e is likely to go extinct in the near future. However, if mosquito control campaigns are effective at reducing malaria, recovery can still occur. These findings emphasize the urgency of ongoing mosquito control efforts, demonstrating hope for a species nearing the brink of extinction. More broadly, our study provides a detailed examination of genomic diversity, inbreeding depression, and extinction risk in a collapsing adaptive radiation, with implications for conservation of other endangered island species.

Introduced pathogens exert novel selection on hosts, and although many host species have experienced drastic population declines in the absence of adaptation, some hosts have adapted to highly virulent pathogens. For instance, mosquitoes and Plasmodium relictum introduced to the Hawaiian Islands have resulted in extinctions and catastrophic population declines due to avian malaria, particularly in the diverse clade of Hawaiian honeycreepers. However, some species, such as the Hawai'i 'amakihi (Chlorodrepanis virens), can survive infection. Immunity exists in low-elevation populations where mosquitoes are abundant, whereas high-elevation, unexposed populations of 'amakihi display greatly reduced immunity. To explore the basis of adaptation to P. relictum in low-elevation 'amakihi, we sequenced transcriptomes from 24 low-elevation and 15 high-elevation 'amakihi. We tested for differential gene expression between (i) infected and uninfected birds and (ii) low- and high-elevation birds. Infected birds showed significant differences in expression across many transcripts with diverse cellular functions involved in different pathways of immune response; eight of the top 13 transcripts blasted to genes previously implicated in immunity to malaria in 'amakihi, and 11 have been identified in other infectious disease systems. Thirteen transcripts showed a trend of higher expression in high-elevation birds. These transcripts blasted to genes involved in metabolism, blood coagulation, and immune response. Our results provide increasing support for a subset of genes involved in immunity to malaria in 'amakihi and hint at possible antagonistic interactions between response to pathogens and environmental characteristics associated with elevation. Further work clarifying the nature of these interactions could benefit conservation efforts of Hawaiian honeycreepers in upper elevation refugia that are increasingly subject to malaria exposure.

The majority of raptor species reside in the tropics, yet very little is known about their movement ecology. However, quantifying movement behavior can provide otherwise elusive information on resource needs, habitat selection, and ecological constraints, which is important for understanding ecological patterns and the management of species of conservation concern. On the Island of Hawai‘i, Hawai‘i, USA, the endemic ‘Io, or Hawaiian Hawk (Buteo solitarius), is a species of conservation concern that little is known of their movement ecology, yet they are dependent on a fragmented and rapidly changing environment. We tracked 15 individuals for up to 18 months across a diverse landscape on the eastern side of the island. We found that all ‘Io occupied a relatively small geographic area, their place of residency, where they spent all or most of their time. However, 10 individuals also exhibited an alternative movement pattern, where individuals repeatedly commuted back and forth between their place of residency to another, geographically disjunct location. These commuter periods, which could last from 24–180 days, were characterized by frequent (9–259) movements, with individual trips lasting 4–77 h away from their place of residency and 12–47 h in between commuter trips. In most cases, individuals went to the same non-contiguous commuting destination, even across multiple commuting sessions, indicating high fidelity to commuting locations. The ‘Io is a forest adapted Buteo but occurs across a diverse landscape from forest to agriculture lands to urban areas. Habitat selection analysis indicated high individual variation among different birds, but generally a preference for forest patches at localized levels. The discovery of the alternative commuting strategy for many ‘Io represents a cryptic movement pattern in the species, demonstrating the power of small, long-lived Global Position System tracking devices to track movement and providing important insights into the ecology of a tropical island raptor.

Low-amplitude "whisper songs" are a taxonomically broad phenomenon in birds that could play an important role in the suite of behaviors birds use to communicate. Due to its cryptic nature, there are inherent difficulties in capturing high-quality whisper song recordings without interrupting natural behaviors. Thus, the whisper song acoustic structure is poorly understood and its potential function remains the subject of debate. Here, we present one of the first quantitative assessments of the acoustic structure of whisper song in birds. Using an innovative microphone transmitter, we collected high-quality recordings of broadcast and whisper songs from the Myadestes obscurus ('& Omacr;ma'o), a thrush species endemic to the Island of Hawai'i. The transmitter was attached to the birds and broadcasted radio signals of all vocalizations produced by the individual to distances over 100 m away that minimized disruption of the birds' normal behavior while recording. We demonstrate that M. obscurus whisper songs are a distinct class of vocalization that differs from broadcast songs in acoustic characteristics beyond amplitude, such as song length, frequency, and length of silent intervals between notes. These findings, in conjunction with habitat-associated variation in the rate at which M. obscurus emit these vocalization classes, indicate broadcast and whisper songs likely serve separate functions. This work provides evidence supporting the acoustic adaptation hypothesis that posits that densely vegetated habitats promote the evolution of songs with specific acoustic features that maintain signal integrity as the sound propagates through the environment. center dot Low-amplitude whisper song is produced by many bird species, and may serve important functions that aid in bird communication, but it remains poorly understood.center dot We employed an underutilized recording technology that allows for individual-specific acoustic data collection to study the acoustic structure of whisper song in greater depth than has been possible with other methods.center dot Our study revealed significant differences in the acoustic characteristics of Myadestes obscurus ('& Omacr;ma'o) broadcast and whisper songs.center dot The structural differences between these 2 vocalization classes, as well as their association with specific habitat characteristics, suggest they serve different functions.center dot '& Omacr;ma'o whisper song structure aligns with the acoustic adaptation hypothesis, which predicts adaptations for sound transmission in densely vegetated environments. Los "cantos susurrados" de baja amplitud son un fen & oacute;meno taxon & oacute;micamente amplio en las aves que podr & iacute;a desempe & ntilde;ar un papel importante en el conjunto de comportamientos que utilizan para comunicarse. Debido a su naturaleza cr & iacute;ptica, existen dificultades inherentes para capturar grabaciones de alta calidad de los cantos susurrados sin interrumpir los comportamientos naturales. Por lo tanto, la estructura ac & uacute;stica de los cantos susurrados est & aacute; poco entendida y su funci & oacute;n potencial sigue siendo objeto de debate. Aqu & iacute; presentamos una de las primeras evaluaciones cuantitativas de la estructura ac & uacute;stica de los cantos susurrados en aves. Utilizando un innovador micr & oacute;fono transmisor, recopilamos grabaciones de alta calidad de los cantos de emisi & oacute;n y susurro de Myadestes obscurus ('& Omacr;ma'o), una especie de zorzal end & eacute;mica de la Isla de Haw & aacute;i. El transmisor se fij & oacute; a las aves y transmiti & oacute; se & ntilde;ales de radio de todas las vocalizaciones producidas por el individuo a distancias de m & aacute;s de 100 m, lo que minimiz & oacute; la interrupci & oacute;n del comportamiento normal de las aves durante la grabaci & oacute;n. Demostramos que los cantos susurrados de M. obscurus son una clase distinta de vocalizaci & oacute;n que difiere de los cantos de emisi & oacute;n en sus caracter & iacute;sticas ac & uacute;sticas m & aacute;s all & aacute; de la amplitud, como la duraci & oacute;n de la canci & oacute;n, la frecuencia y la longitud de los intervalos silenciosos entre notas. Estos hallazgos, junto con la variaci & oacute;n asociada al h & aacute;bitat en la frecuencia con la que M. obscurus emite estas clases de vocalizaciones, indican que los cantos de emisi & oacute;n y susurro probablemente cumplen funciones separadas. Este trabajo brinda evidencia que respalda la hip & oacute;tesis de adaptaci & oacute;n ac & uacute;stica, que postula que los h & aacute;bitats densamente vegetados promueven la evoluci & oacute;n de cantos con caracter & iacute;sticas ac & uacute;sticas espec & iacute;ficas que mantienen la integridad de la se & ntilde;al mientras el sonido se propaga por el entorno.

The yǻyaguak (Mariana swiftlet; Aerodramus bartschi ) is an endangered cave-nesting species historically found on Guam and the southern Mariana Islands, Micronesia. The population on Guam has been severely affected by the introduction of the brown treesnake Boiga irregularis . Population status assessments have, however, been challenging due to the limitations of traditional counting methods, which rely on visual observations at cave entrances and are prone to inaccuracies. To improve count accuracy, we estimated yǻyaguak population size and relative nesting activity using thermal and near-infrared videography. The population on Guam was surveyed at the island’s 3 known occupied caves (Mahlac, Maemong, and Fachi) between 2019 and 2023. Mahlac Cave harbored the largest colony, which ranged from 506 to 665 birds; Maemong Cave held 144 to 196 birds; and Fachi Cave, which is sometimes flooded, had 28 (in 2019) and 35 birds (in 2023). Our estimates indicate a slight decline in the yǻyaguak population over the study period. This study demonstrates the potential of thermal and near-infrared videography for improved monitoring of yǻyaguak colonies and nesting activity, which will contribute to our understanding of population dynamics and the effectiveness of management strategies such as brown treesnake control.

ABSTRACTThe animal gut microbiome can have a strong influence on the health, fitness, and behavior of its hosts. The composition of the gut microbial community can be influenced by factors such as diet, environment, and evolutionary history (phylosymbiosis). However, the relative influence of these factors is unknown in most bird species. Furthermore, phylosymbiosis studies have largely focused on clades that diverged tens of millions of years ago, and little is known about the degree of gut microbiome divergence in more recent species radiations. This study explores the drivers of microbiome variation across the unique and recent Hawaiian honeycreeper radiation (Fringillidae: Drepanidinae). Fecal samples were collected from 14 extant species spanning the main islands of the Hawaiian archipelago and were sequenced using three metabarcoding markers to characterize the gut microbiome, invertebrate diet, and plant diet of Hawaiian honeycreepers. We then used these metabarcoding data and the honeycreeper host phylogeny to evaluate their relative roles in shaping the gut microbiome. Microbiome variation across birds was highly individualized; however, source island had a small but significant effect on microbiome structure. The microbiomes did not recapitulate the host phylogenetic tree, indicating that evolutionary history does not strongly influence microbiome structure in the honeycreeper clade. These results expand our understanding of the roles of diet, geography, and phylogeny on avian microbiome structure, while also providing important ecological information about the diet and gut microbiota of wild Hawaiian honeycreepers.

Abstract Gape‐limited predators (e.g., snakes, many fish) are not generally expected to pose a predation threat to prey that are too large for them to swallow. However, the extent to which snakes predate on prey that exceed their gape limitation remains largely unknown. We conducted the first study to investigate the influence of both prey and predator sizes on the frequency of ingestion success by snakes in a natural system. We combined survival monitoring of an avian prey species (Aplonis opaca) via radio‐telemetry with a survey of the size distribution of their major predator (Boiga irregularis) on Guam. This allowed us to assess (1) the frequency of unsuccessful ingestion by the predator, (2) whether the size of the prey predicts ingestion success, (3) whether the size of the predator predicts ingestion success, and (4) the relationship between prey and predator sizes in successful ingestion attempts. We found that nearly half (47.95%) of ingestion attempts by snakes on fledgling birds were unsuccessful, and no instances where unsuccessful ingestion caused the mortality of the snake. Attempts to consume smaller fledglings were as likely to be unsuccessful as attempts to swallow larger fledglings. However, snakes that successfully ingested fledglings were among the largest snakes in the population, and larger than average conspecifics attracted to endothermic prey. The smallest snakes that successfully ingested fledglings attained remarkably high relative prey mass values for their species, consuming prey weighing up to 79.9% of their own mass. Our study indicates that B. irregularis routinely predate prey that are too large for them to successfully ingest, which causes mortality to the prey but poses little risk to the predator. The potential reward for snakes in consuming oversized prey may outweigh the inherent risks, while instances of predation that do not result in consumption may have considerable impacts on prey populations.

Plasmodium parasites infect thousands of species and provide an exceptional system for studying hostpathogen dynamics, especially for multi-host pathogens. However, understanding these interactions requires an accurate assay of infection. Assessing Plasmodium infections using microscopy on blood smears often misses infections with low parasitemias (the fractions of cells infected), and biases in malaria prevalence estimates will differ among hosts that differ in mean parasitemias. We examined Plasmodium relictum infection and parasitemia using both microscopy of blood smears and quantitative polymerase chain reaction (qPCR) on 299 samples from multiple bird species in Hawai'i and fit models to predict parasitemias from qPCR cycle threshold (Ct) values. We used these models to quantify the extent to which microscopy underestimated infection prevalence and to more accurately estimate infection patterns for each species for a large historical study done by microscopy. We found that most qPCR-positive wild-caught birds in Hawaii had low parasitemias (Ct scores >= 35), which were rarely detected by microscopy. The fraction of infections missed by microscopy differed substantially among eight species due to differences in species' parasitemia levels. Infection prevalence was likely 4-5-fold higher than previous microscopy estimates for three introduced species, including Zosterops japonicus, Hawaii's most abundant forest bird, which had low average parasitemias. In contrast, prevalence was likely only 1.5-2.3-fold higher than previous estimates for Himatione sanguinea and Chlorodrepanis virens, two native species with high average parasitemias. Our results indicate that relative patterns of infection among species differ substantially from those observed in previous microscopy studies, and that differences depend on variation in parasitemias among species. Although microscopy of blood smears is useful for estimating the frequency of different Plasmodium stages and host attributes, more sensitive quantitative methods, including qPCR, are needed to accurately estimate and compare infection prevalence among host species. (c) 2023 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.

Habitat loss and fragmentation are considered the greatest threats to ecosystems worldwide. Movement reveals how individuals meet their habitat requirements and respond to environmental heterogeneity, and thus can provide a powerful tool for investigating how animals respond to changes in landscape configuration. In our study, we examined the effects of landscape configuration on the space use and movement strategies of four endemic Hawaiian forest bird species spanning a range of foraging guilds (i.e. frugivore, nectivore, generalist). We used a landscape‐level automated radio tracking system to measure location data of 127 individuals tracked on Hawaiʻi Island in a naturally fragmented landscape created by volcanic activity in the mid‐ to late‐1800s and a nearby continuous landscape. We found that landscape configuration had a strong effect on movement patterns and space‐use of all four species. In the fragmented landscape, all species predominately occupied a single forest patch, displayed a high degree of area‐restricted search behavior, with few long‐distance movements away from their primary forest patch. These patterns contrasted significantly with those of conspecifics in the continuous landscape which exhibited relatively unconstrained movements across the forested landscape and had 3‐ to 12‐fold larger home ranges. Our findings indicate that landscape structure plays a strong role in shaping movement behavior of a tropical bird community and provides valuable insights into the behavioral mechanisms that may be important for species to persist within fragmented landscapes.

Similar to other single-island endemic Hawaiian honeycreepers, the critically endangered ‘ākohekohe (Palmeria dolei) is threatened by climate-driven disease spread. To avert the imminent risk of extinction, managers are considering novel measures, including the conservation introduction (CI) of ‘ākohekohe from Maui to higher elevation habitats on the Island of Hawai’i. This study integrated lidar-based habitat suitability models (LHSMs) and population viability analyses (PVAs) to assess five candidate sites currently considered by managers for CI. We first developed an LHSM for the species’ native range on Maui. We then projected habitat suitability across candidate CI sites, using forest structure and topography metrics standardized across sensor types. Given the structural variability observed within the five candidate sites, we identified clusters of contiguous, highly suitable habitat as potential release sites. We then determined how many adult individuals could be supported by each cluster based on adult home range estimates. To determine which clusters could house the minimum number of ‘ākohekohe birds necessary for a stable or increasing future population, we conducted PVAs under multiple scenarios of bird releases. We found that canopy height and relative height 90 had the greatest effects on model performance, possibly reflecting ‘ākohekohe’s preference for taller canopies. We found that a small release of at least nine pairs of equal sex ratios were sufficient for an 80% chance of success and a <1% chance of extirpation in 20 years, resulting in a minimum release area of 4.5 ha in size. We integrated the results of the LHSM and PVA into an interactive web application that allowed managers to consider the caveats and uncertainties associated with both LHSMs and PVAs in their decision-making process. As climate change continues to threaten species worldwide, this research demonstrates the value of lidar remote sensing combined with species-specific models to enable rapid, quantitative assessments that can inform the increasing consideration of time-sensitive conservation introductions.

To cope with climate change, species may shift their distributions or adapt in situ to changing environmental conditions. However, clear examples of genetic changes via adaptation are limited. We explore evolutionary responses to climate change in the endangered southwestern willow flycatcher ( Empidonax traillii extimus ) through whole-genome comparisons between historical specimens, collected from 1888 to 1909 near San Diego, California, United States, and contemporary individuals from across the breeding range. Genomic analyses revealed that introgression into San Diego increased adaptive potential over time and shifted genome-wide population structure towards that of neighbouring populations. In contrast, loci linked to climate (dew point temperature and precipitation) shifted away from neighbouring populations and in a direction consistent with adaptation to climate change in southern California. This research highlights the role of admixture in facilitating adaptive shifts through its impact on genome-wide genetic variation and represents one of the few studies to document climate adaptation in a wild population.

A key component for biologists managing mobile species is understanding where and when a species occurs at different locations and scaling management to fit the spatial and temporal patterns of movement. We established an automated radio-telemetry tracking network to document multi-year movement in 2016-2018 of 3 endangered waterbirds among wetlands on OModified Letter Turned Commaahu, HawaiModified Letter Turned Commai, USA: Modified Letter Turned Commaalae Modified Letter Turned Commaula or Hawaiian gallinule (gallinule; Gallinula galeata sandvicensis), Modified Letter Turned Commaalae keModified Letter Turned CommaokeModified Letter Turned Commao or Hawaiian coot (coot; Fulica alai), and aeModified Letter Turned Commao or Hawaiian stilt (stilt; Himantopus mexicanus knudseni), each with different ecological requirements. There were marked differences in the movement propensity of the species, with no movement among sites detected in gallinules, 31% of coots moving among wetlands, and very high levels of daily movement in stilts. A network analysis revealed strong evidence for fidelity among individual stilts to specific wetlands, indicating different groups of wetlands supported different birds. There was also strong evidence for patterns in daily and seasonal movement patterns of stilts. Our work indicates the importance of each wetland to the waterbirds they support, as each individual had strong fidelity to a single wetland. In addition, for Hawaiian coots and stilts, which were documented moving among multiple wetlands, a network of wetlands may be key for long-term persistence of these endangered species, and coordinated regional management of waterbirds as a shared resource could provide greater benefits to waterbirds than independent management of each wetland.

The recent development of animal-borne sensors coupled with location data can provide insights into how individuals modify their behaviour with respect to specific habitat features. Animals can express a diverse array of behaviours as they navigate heterogenous landscapes, yet few studies have specifically evaluated the interaction of behaviours with habitat characteristics. We used a novel broadcast acoustic transmitter to investigate the interaction between vocal behaviours of an endemic Hawaiian thrush, the ʻōmaʻo, Myadestes obscurus, and habitat features across a naturally fragmented forest landscape. Through the development of behavioural landscape models that link specific vocalizations with space use, we found that the use of different vocalization types (calls, songs, whisper songs) were highly variable across the landscape but were associated with distinct habitat features. The likelihood of calls increased in an open lava matrix between forest patches, while whisper songs were more strongly associated with the dense interior areas of forest fragments. In contrast, the rate of ʻōmaʻo vocalizations overall decreased in the open lava matrix, suggesting that ʻōmaʻo may shift behaviours from territory defence to foraging as they transition through different habitats. Our study revealed context-specific changes in behaviour across ʻōmaʻo home ranges, including courtship, aggression and social interactions between individuals. Combining the use of a novel acoustic tool with automated radiotelemetry allowed us to overcome challenges associated with detection and analysis of variation in behaviour and resource selection across a highly heterogeneous landscape that would have been otherwise difficult to impossible.

Many species around the world are declining precipitously as a result of multiple threats and changing climate. Managers tasked with protecting species often face difficult decisions in regard to identifying which threats should be addressed, given limited resources and uncertainty in the success of any identified management action. On Kaua'i Island, Hawai'i, USA, forest bird species have experienced accelerated declines over the last 20 years, and 2 species, the 'akikiki (Oreomystis bairdi) and 'akeke'e (Loxops caeruleirostris), are now at the brink of extinction. Both species face multiple threats, and managers face difficult decisions on whether to mitigate threats in the wild, establish a captive population as insurance against extinction, translocate birds to novel locations, or some combination of these actions. Each set of actions (alternatives) would require substantial resources with considerable uncertainty in success. In 2014, we brought together 14 experts representing biologists and managers familiar with the species and island to develop a conservation strategy under a structured decision making (SDM) framework, an approach for making complex decisions under uncertainty. The group's challenge was to identify a set of alternatives that reduces the risk of extinction, set the foundation for one or more genetically viable, reproducing, stable to increasing populations in 10 years, and promote conditions for long-term persistence in the wild. Multiple alternatives were evaluated, via expert judgement, in terms of the probability they would achieve the objectives concerning immediate extinction risk, near-term viability, and adequacy of habitat. Factors that might impede the success of each action were also evaluated. The process identified the establishment of a captive population and efforts to stabilize the existing wild population as the approach most likely to meet the objectives of preventing imminent extinction and ensuring long-term viability.

Abstract A major advancement in the use of radio telemetry has been the development of automated radio tracking systems (ARTS), which allow animal movements to be tracked continuously. A new ARTS approach is the use of a network of simple radio receivers (nodes) that collect radio signal strength (RSS) values from animal‐borne radio transmitters. However, the use of RSS‐based localization methods in wildlife tracking research is new, and analytical approaches critical for determining high‐quality location data have lagged behind technological developments. We present an analytical approach to optimize RSS‐based localization estimates for a node network designed to track fine‐scale animal movements in a localized area. Specifically, we test the application of analytical filters (signal strength, distance among nodes) to data from real and simulated node networks that differ in the density and configuration of nodes. We evaluate how different filters and network configurations (density and regularity of node spacing) may influence the accuracy of RSS‐based localization estimates. Overall, the use of signal strength and distance‐based filters resulted in a 3‐ to 9‐fold increase in median accuracy of location estimates over unfiltered estimates, with the most stringent filters providing location estimates with a median accuracy ranging from 28 to 73 m depending on the configuration and spacing of the node network. We found that distance filters performed significantly better than RSS filters for networks with evenly spaced nodes, but the advantage diminished when nodes were less uniformly spaced within a network. Our results not only provide analytical approaches to greatly increase the accuracy of RSS‐based localization estimates, as well as the computer code to do so, but also provide guidance on how to best configure node networks to maximize the accuracy and capabilities of such systems for wildlife tracking studies.