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Abstract: Advances in hierarchical modeling have improved estimation of ecological parameters from count data, especially those quantifying population abundance, distribution, and dynamics by explicitly accounting for observation processes, particularly incomplete detection. Even hierarchical models that account for incomplete detection, however, cannot compensate for data limitations stemming from poorly planned sampling. Ecologists therefore need guidance for planning count‐based studies that follow established sampling theory, collect appropriate data, and apply current modeling approaches to answer their research questions. We synthesize available literature relevant to guiding count‐based studies. Considering the central historical and ongoing contributions of avian studies to ecological knowledge, we focus on birds as a case study for this review, but the basic principles apply to all populations whose members are sufficiently observable to be counted. The sequence of our review represents the thought process in which we encourage ecologists to engage 1) the research question(s) and population parameters to measure, 2) sampling design, 3) analytical framework, 4) temporal design, and 5) survey protocol. We also provide 2 hypothetical demonstrations of these study plan components representing different research questions and study systems. Mirroring the structure of hierarchical models, we suggest researchers primarily focus on the ecological processes of interest when designing their approach to sampling, and wait to consider logistical constraints of data collection and observation processes when developing the survey protocol. We offer a broad framework for researchers planning count‐based studies, while pointing to relevant literature elaborating on particular tools and concepts.

Abstract: Background: Contemporary and projected shifts in global fire regimes highlight the importance of understanding how fire affects ecosystem function and biodiversity across taxa and geographies. Pyrodiversity, or heterogeneity in fire history, is often an important driver of biodiversity, though it has been largely overlooked until relatively recently. In this paper, we synthesise previous research to develop a theoretical framework on pyrodiversity–biodiversity relationships and propose future research and conservation management directions. Theoretical Framework: Pyrodiversity may affect biodiversity by diversifying available ecological niches, stabilising community networks and/or supporting diverse species pools available for post‐fire colonisation. Further, pyrodiversity's effects on biodiversity vary across different spatial, temporal and organismal scales depending on the mobility and other life history traits of the organisms in question and may be mediated by regional eco‐evolutionary factors such as historical fire regimes. Developing a generalisable understanding of pyrodiversity effects on biodiversity has been challenging, in part because pyrodiversity can be quantified in various ways. Applying the Pyrodiversity Concept: Exclusion of Indigenous fire stewardship, fire suppression, increased unplanned ignitions and climate change have led to dramatic shifts in fire regimes globally. Such shifts include departures from historic levels of pyrodiversity and add to existing challenges to biodiversity conservation in fire‐prone landscapes. Managers navigating these challenges can be aided by targeted research into observed contemporary pyrodiversity–biodiversity relationships as well as knowledge of historical reference conditions informed by both Indigenous and local ecological knowledge and western science. Future Research Directions: Several promising avenues exist for the advancement of pyrodiversity science to further both theoretical and practical goals. These lines of investigation include but are not limited to (1) testing the increasing variety of pyrodiversity metrics and analytical approaches; (2) assessing the spatial and temporal scale‐dependence of pyrodiversity's influence; (3) reconstructing historical pyrodiversity patterns and developing methods for predicting and/or promoting future pyrodiversity; and (4) expanding the focus of pyrodiversity science beyond biodiversity to better understand its influence on ecosystem function and processes more broadly.

Abstract: Over recent decades, our understanding of climate change has accelerated greatly, but unfortunately, observable impacts have increased in tandem. Both mitigation and adaptation have not progressed at the level or scale warranted by our collective knowledge on climate change. More effective approaches to engage people on current and future anthropogenic climate change effects are urgently needed. Here, we show how species whose distributions are shifting in response to climate change, that is, ‘species‐on‐the‐move’, present an opportunity to engage people with climate change by linking to human values, and our deep connections with the places in which we live, in a locally relevant yet globally coherent narrative. Species‐on‐the‐move can impact ecosystem structure and function, food security, human health, livelihoods, culture and even the climate itself through feedback to the climate system, presenting a wide variety of potential pathways for people to understand that climate change affects them personally as individuals. Citizen science focussed on documenting changes in biodiversity is one approach to foster a deeper engagement on climate change. However, other possible avenues, which may offer potential to engage people currently unconnected with nature, include arts, games or collaborations with rural agriculture (e.g. new occurrences of pest species) or fisheries organisations (e.g. shifting stocks) or healthcare providers (e.g. changing distributions of disease vectors). Through the importance we place on the aspects of life impacted by the redistribution of species around us, species‐on‐the‐move offer emotional pathways to connect with people on the complex issue of climate change in profound ways that have the potential to engender interest and action on climate change. Read the free Plain Language Summary for this article on the Journal blog.

Changes in phenology in response to ongoing climate change have been observed in numerous taxa around the world. Differing rates of phenological shifts across trophic levels have led to concerns that ecological interactions may become increasingly decoupled in time, with potential negative consequences for populations. Despite widespread evidence of phenological change and a broad body of supporting theory, large-scale multitaxa evidence for demographic consequences of phenological asynchrony remains elusive. Using data from a continental-scale bird-banding program, we assess the impact of phenological dynamics on avian breeding productivity in 41 species of migratory and resident North American birds breeding in and around forested areas. We find strong evidence for a phenological optimum where breeding productivity decreases in years with both particularly early or late phenology and when breeding occurs early or late relative to local vegetation phenology. Moreover, we demonstrate that landbird breeding phenology did not keep pace with shifts in the timing of vegetation green-up over a recent 18-y period, even though avian breeding phenology has tracked green-up with greater sensitivity than arrival for migratory species. Species whose breeding phenology more closely tracked green-up tend to migrate shorter distances (or are resident over the entire year) and breed earlier in the season. These results showcase the broadest-scale evidence yet of the demographic impacts of phenological change. Future climate change-associated phenological shifts will likely result in a decrease in breeding productivity for most species, given that bird breeding phenology is failing to keep pace with climate change.

Outdoor recreation benefits local economies, environmental education, and public health and wellbeing, but it can also adversely affect local ecosystems. Human presence in natural areas alters feeding and reproductive behaviors, physiology, and population structure in many wildlife species, often resulting in cascading effects through entire ecological communities. As outdoor recreation gains popularity, existing trails are becoming overcrowded and new trails are being built to accommodate increasing use. Many recreation impact studies have investigated effects of the presence or absence of humans while few have investigated recreation effects on wildlife using a gradient of disturbance intensity. We used camera traps to quantify trail use by humans and mid- to large-sized mammals in an area of intense outdoor recreation–the Upper East River Valley, Colorado, USA. We selected five trails with different types and intensities of human use and deployed six cameras on each trail for five weeks during a COVID-enhanced 2020 summer tourism season. We used occupancy models to estimate detectability and habitat use of the three most common mammal species in the study area and determined which human activities affect the habitat use patterns of each species. Human activities affected each species differently. Mule deer (Odocoileus hemionus) tended to use areas with more vehicles, more predators, and greater distances from the trailhead, and they were more likely to be detected where there were more bikers. Coyotes (Canis latrans) and red foxes (Vulpes vulpes) were most likely to use areas where their prey species occurred, and foxes were more likely to be detected where the vegetation was shorter. Humans and their recreational activities differentially influence different species. More generally, these results reinforce that it is unlikely that a single management policy is suitable for all species and management should thus be tailored for each target species.

Climate change is driving a rapid but highly variable redistribution of life on Earth, comparable in scale and magnitude to changes historically only seen over tens of thousands of years. Despite increased research effort, the complex mechanisms driving these changes in geographical distribution of species, or ‘range shifts’, remain only superficially understood. Attempts to understand the processes underpinning species responses are hampered by the paucity of comprehensive, longterm datasets, few theoretical frameworks, and lack of strategic direction and cross-fertilisation with related ecological fields. As an emerging, dynamic field, range shift ecology would benefit from integrating concepts and approaches from other related, more established areas of research, such as invasion ecology. Here, we use a systematic literature review and bibliographic analysis to assess the level of knowledge exchange between range shift ecology and invasion ecology. We found that while the two fields are inherently strongly related, the level of exchange and integration of ideas via citation networks does not reflect the closeness of the fields in terms of concepts, theories, and practice. Although range shift papers cite invasion papers more often than vice versa, the citation rate is generally quite low for both. These findings are evidence of the increasing need to move away from discipline-focused interpretation and communication of scientific results, towards greater research integration and connection between related ecological fields. Increased knowledge and data exchange between range shift and invasion fields could improve mechanistic understanding of range shifts and species invasions under climate change, enhance the predictive capacity of models and better inform management and conservation efforts.

Rare birds known as "accidentals" or "vagrants" have long captivated birdwatchers and puzzled biologists, but the drivers of these rare occurrences remain elusive. Errors in orientation or navigation are considered one potential driver: migratory birds use the Earth's magnetic field-sensed using specialized magnetoreceptor structures-to traverse long distances over often unfamiliar terrain. Disruption to these magnetoreceptors or to the magnetic field itself could potentially cause errors leading to vagrancy. Using data from 2 million captures of 152 landbird species in North America over 60 years, we demonstrate a strong association between disruption to the Earth's magnetic field and avian vagrancy during fall migration. Furthermore, we find that increased solar activity-a disruptor of the avian magnetoreceptor-generally counteracts this effect, potentially mitigating misorientation by disabling the ability for birds to use the magnetic field to orient. Our results link a hypothesized cause of misorientation to the phenomenon of avian vagrancy, further demonstrating the importance of magnetoreception among the orientation mechanisms of migratory birds. Geomagnetic disturbance may have important downstream ecological consequences, as vagrants may experience increased mortality rates or facilitate range expansions of avian populations and the organisms they disperse.

In conifer forests of western North America, wildlife populations can change rapidly in the decade following wildfire as trees die and animals respond to concomitant resource pulses that occur across multiple trophic levels. In particular, black-backed woodpeckers (Picoides arcticus) show predictable temporal increases then declines following fire; this trajectory is widely believed to be a response to the woodpeckers' main prey, woodboring beetle larvae of the families Buprestidae and Cerambycidae, but we lack understanding of how abundances of these predators and prey may be associated in time or space. Here, we pair woodpecker surveys over 10 years with surveys of woodboring beetle sign and activity, collected at 128 survey plots across 22 recent fires, to ask whether accumulated beetle sign indicates current or past black-backed woodpecker occurrence, and whether that relationship is mediated by the number of years since fire. We test this relationship using an integrative multi-trophic occupancy model. Our results demonstrate that woodboring beetle sign is a positive indicator of woodpecker presence 1-3 years following fire, an uninformative indicator from 4-6 years after fire, and a negative indicator beginning 7 years following fire. Woodboring beetle activity, itself, is temporally variable and dependent on tree species composition, with beetle sign generally accumulating over time, particularly in stands with diverse tree communities, but decreasing over time in Pinus-dominated stands where faster bark decay rates lead to brief pulses of beetle activity followed by rapid degradation of tree substrate and accumulated beetle sign. Altogether, the strong connections of woodpecker occurrence to beetle activity support prior hypotheses of how multi-trophic interactions govern rapid temporal dynamics of primary and secondary consumers in burned forests. While our results indicate that beetle sign is, at best, a rapidly shifting and potentially misleading measure of woodpecker occurrence, the better we understand the interacting mechanisms underlying temporally dynamic systems, the more successfully we will be able to predict the outcomes of management actions.

Species' response to rapid climate change can be measured through shifts in timing of recurring biological events, known as phenology. The Gulf of Maine is one of the most rapidly warming regions of the ocean, and thus an ideal system to study phenological and biological responses to climate change. A better understanding of climate-induced changes in phenology is needed to effectively and adaptively manage human-wildlife conflicts. Using data from a 20+ year marine mammal observation program, we tested the hypothesis that the phenology of large whale habitat use in Cape Cod Bay has changed and is related to regional-scale shifts in the thermal onset of spring. We used a multi-season occupancy model to measure phenological shifts and evaluate trends in the date of peak habitat use for North Atlantic right (Eubalaena glacialis), humpback (Megaptera novaeangliae), and fin (Balaenoptera physalus) whales. The date of peak habitat use shifted by +18.1 days (0.90 days/year) for right whales and +19.1 days (0.96 days/year) for humpback whales. We then evaluated interannual variability in peak habitat use relative to thermal spring transition dates (STD), and hypothesized that right whales, as planktivorous specialist feeders, would exhibit a stronger response to thermal phenology than fin and humpback whales, which are more generalist piscivorous feeders. There was a significant negative effect of western region STD on right whale habitat use, and a significant positive effect of eastern region STD on fin whale habitat use indicating differential responses to spatial seasonal conditions. Protections for threatened and endangered whales have been designed to align with expected phenology of habitat use. Our results show that whales are becoming mismatched with static seasonal management measures through shifts in their timing of habitat use, and they suggest that effective management strategies may need to alter protections as species adapt to climate change.

Fire is an integral component of ecosystems globally and a tool that humans have harnessed for millennia. Altered fire regimes are a fundamental cause and consequence of global change, impacting people and the biophysical systems on which they depend. As part of the newly emerging Anthropocene, marked by human-caused climate change and radical changes to ecosystems, fire danger is increasing, and fires are having increasingly devastating impacts on human health, infrastructure, and ecosystem services. Increasing fire danger is a vexing problem that requires deep transdisciplinary, trans-sector, and inclusive partnerships to address. Here, we outline barriers and opportunities in the next generation of fire science and provide guidance for investment in future research. We synthesize insights needed to better address the long-standing challenges of innovation across disciplines to (i) promote coordinated research efforts; (ii) embrace different ways of knowing and knowledge generation; (iii) promote exploration of fundamental science; (iv) capitalize on the "firehose" of data for societal benefit; and (v) integrate human and natural systems into models across multiple scales. Fire science is thus at a critical transitional moment. We need to shift from observation and modeled representations of varying components of climate, people, vegetation, and fire to more integrative and predictive approaches that support pathways toward mitigating and adapting to our increasingly flammable world, including the utilization of fire for human safety and benefit. Only through overcoming institutional silos and accessing knowledge across diverse communities can we effectively undertake research that improves outcomes in our more fiery future.

Community assembly theory hypothesizes that two main niche-based processes act to shape composition and organization of biological assemblages: abiotic filtering and biological interactions. Here, we conducted repeated surveys of bird abundance along an undisturbed elevational gradient in the tropical Andes to investigate 1) signals of deterministic processes driving community assembly and 2) potential mechanisms by which these forces operate (temperature, habitat complexity, fruit and insect availability), while correcting for imperfect detection and modeling species abundances with N-mixture models. We observed strong signals of abiotic filtering driving functionally and phylogenetically clustered assemblages towards higher elevations, and a weaker signal of limiting similarity resulting in few overdispersed assemblages at lower elevations. Whereas the decay in species richness with increasing elevation was explained by temperature, trait and phylogenetic dispersion were explained by both temperature and vegetation structure, implying that an interplay of abiotic and biotic mechanisms determines abundance-based community structure in our montane assemblages. Interestingly, trait and phylogenetic dispersion consistently decreased until ~3000 m but increased above this elevation, highlighting a potential role of competition in resource-scarce habitats. Combined, our findings suggest abiotic filters are still the main process shaping montane biotas across elevations, whereas resource availability might act locally upon assemblages further modifying them. Our study challenges recent studies in tropical mountains that suggest that biotic filters are a stronger force than abiotic filters in shaping tropical montane assemblages, and exemplifies how accounting for imperfect detection might overcome potential biases in detecting environmental filtering signals in community assembly studies.

Aim: Citizen science data are increasingly used for modelling species distributions because they offer broad spatiotemporal coverage of local observations. However, such data are often collected without experimental design or set survey methods, raising the risk that bias and noise will compromise modelled predictions. We tested the ability of species distribution models (SDMs) built from these low-structure citizen science data to match the quality of SDMs from systematically collected data and tested whether stringent data filtering improved predictions. Location: Northeastern USA. Methods: We evaluated models built from a rapidly growing dataset of avian occurrences reported by birders—eBird—against models built from four independent, systematically collected datasets. We developed SDMs for 96 species using both data sources and compared their predictive abilities. We also tested whether culling eBird data by applying stringent data filters on survey effort or observer expertise improved predictions. Results: We found that SDMs built from low-structure citizen science data matched or exceeded performance of SDMs from systematically collected datasets for 12%–31% of species ((Formula presented.) = 22%), depending on the dataset. At least one culling option produced equivalent or better performance for 40%–70% of species ((Formula presented.) = 49%). Data culling by restricting survey effort improved predictions more than restricting by observer expertise. The optimal effort restriction differed by dataset, and for three of the datasets was further informed by species traits. Main conclusions: Species distribution models developed using low-structure citizen science data sometimes performed as well as those from systematic data. Culling generally improved models, but results were heterogeneous, prohibiting clear recommendations for how to cull. Our results indicate that the growing availability of citizen science data holds potential for creating high-quality spatial predictions, but that time should be invested in determining how best to cull datasets and that one-size-fits-all solutions beyond basic outlier filtering may be hard to find.

Recently burned coniferous forests host wildlife communities that respond to variation in burn severity, post-fire habitat structure, and patch configuration. Habitat selection theory predicts that birds inhabiting these variable post-fire landscapes will select nesting locations that confer an adaptive advantage through increased fitness and reproductive success. Understanding the effect of post-fire habitat on avian nesting ecology can provide valuable information to guide restoration and management after wildfire. The Black-backed Woodpecker (Picoides arcticus) is strongly associated with recently burned forests in the western United States, where it is used as an indicator species for the effects of post-fire forest management. Between 2011 and 2018, we located and monitored 118 Black-backed Woodpecker nests in burned forests of northern California. We evaluated the influence of habitat and nest characteristics on nest site selection and daily nest survival. Our results demonstrate a pattern of neutral congruence between habitat selection and fitness. Blackbacked Woodpeckers showed strong selection for each of the nest habitat variables that we measured: Woodpeckers selected moderately sized trees in areas of high snag density burned at high severity, but also in areas relatively close to low-severity or unburned edges. However, only nest initiation date affected nest survival, with decreased survival in late-season nests. Our results suggest that management actions aimed at maintaining breeding habitat for Black-backed Woodpeckers should prioritize retention and creation of pyrodiverse landscapes that include dense stands of snags (>5 snags per 100 m2) within ~500 m of forest that burned at low severity or remained unburned.

Climatic warming can shift community composition driven by the colonization-extinction dynamics of species with different thermal preferences; but simultaneously, habitat fragmentation can mediate species' responses to warming. As this potential interactive effect has proven difficult to test empirically, we collected data on birds over 10 years of climate warming in a reservoir subtropical island system that was formed 65 years ago. We investigated how the mechanisms underlying climate-driven directional change in community composition were mediated by habitat fragmentation. We found thermophilization driven by increasing warm-adapted species and decreasing cold-adapted species in terms of trends in colonization rate, extinction rate, occupancy rate and population size. Critically, colonization rates of warm-adapted species increased faster temporally on smaller or less isolated islands; cold-adapted species generally were lost more quickly temporally on closer islands. This provides support for dispersal limitation and microclimate buffering as primary proxies by which habitat fragmentation mediates species range shift. Overall, this study advances our understanding of biodiversity responses to interacting global change drivers. [ABSTRACT FROM AUTHOR]

Species respond to climate change in two dominant ways: range shifts in latitude or elevation and phenological shifts of life-history events. Range shifts are widely viewed as the principal mechanism for thermal niche tracking, and phenological shifts in birds and other consumers are widely understood as the principal mechanism for tracking temporal peaks in biotic resources. However, phenological and range shifts each present simultaneous opportunities for temperature and resource tracking, although the possible role for phenological shifts in thermal niche tracking has been widely overlooked. Using a canonical dataset of Californian bird surveys and a detectability-based approach for quantifying phenological signal, we show that Californian bird communities advanced their breeding phenology by 5-12 d over the last century. This phenological shift might track shifting resource peaks, but it also reduces average temperatures during nesting by over 1 °C, approximately the same magnitude that average temperatures have warmed over the same period. We further show that early-summer temperature anomalies are correlated with nest success in a continental-scale database of bird nests, suggesting avian thermal niches might be broadly limited by temperatures during nesting. These findings outline an adaptation surface where geographic range and breeding phenology respond jointly to constraints imposed by temperature and resource phenology. By stabilizing temperatures during nesting, phenological shifts might mitigate the need for range shifts. Global change ecology will benefit from further exploring phenological adjustment as a potential mechanism for thermal niche tracking and vice versa.

The study of the ecology and natural history of species has traditionally ceased when a species goes extinct, despite the benefit to current and future generations of potential findings. We used the extinct Carolina parakeet as a case study to develop a framework investigating the distributional limits, subspecific variation, and migratory habits of this species as a means to recover important information about recently extinct species. We united historical accounts with museum collections to develop an exhaustive, comprehensive database of every known occurrence of this once iconic species. With these data, we combined species distribution models and ordinal niche comparisons to confront multiple conjectured hypotheses about the parakeet's ecology with empirical data on where and when this species occurred. Our results demonstrate that the Carolina parakeet's range was likely much smaller than previously believed, that the eastern and western subspecies occupied different climatic niches with broad geographical separation, and that the western subspecies was likely a seasonal migrant while the eastern subspecies was not. This study highlights the novelty and importance of collecting occurrence data from published observations on extinct species, providing a starting point for future investigations of the factors that drove the Carolina parakeet to extinction. Moreover, the recovery of lost autecological knowledge could benefit the conservation of other parrot species currently in decline and would be crucial to the success of potential de-extinction efforts for the Carolina parakeet.

Consistent with a warming climate, birds are shifting the timing of their migrations, but it remains unclear to what extent these shifts have kept pace with the changing environment. Because bird migration is primarily cued by annually consistent physiological responses to photoperiod, but conditions at their breeding grounds depend on annually variable climate, bird arrival and climate-driven spring events would diverge. We combined satellite and citizen science data to estimate rates of change in phenological interval between spring green-up and migratory arrival for 48 breeding passerine species across North America. Both arrival and green-up changed over time, usually in the same direction (earlier or later). Although birds adjusted their arrival dates, 9 of 48 species did not keep pace with rapidly changing green-up and across all species the interval between arrival and green-up increased by over half a day per year. As green-up became earlier in the east, arrival of eastern breeding species increasingly lagged behind green-up, whereas in the west-where green-up typically became later-birds arrived increasingly earlier relative to green-up. Our results highlight that phenologies of species and trophic levels can shift at different rates, potentially leading to phenological mismatches with negative fitness consequences.

Climate change is shifting the phenology of migratory animals earlier; yet an understanding of how climate change leads to variable shifts across populations, species and communities remains hampered by limited spatial and taxonomic sampling. In this study, we used a hierarchical Bayesian model to analyse 88,965 site‐specific arrival dates from 222 bird species over 21 years to investigate the role of temperature, snowpack, precipitation, the El‐Niño/Southern Oscillation and the North Atlantic Oscillation on the spring arrival timing of Nearctic birds. Interannual variation in bird arrival on breeding grounds was most strongly explained by temperature and snowpack, and less strongly by precipitation and climate oscillations. Sensitivity of arrival timing to climatic variation exhibited spatial nonstationarity, being highly variable within and across species. A high degree of heterogeneity in phenological sensitivity suggests diverging responses to ongoing climatic changes at the population, species and community scale, with potentially negative demographic and ecological consequences. [ABSTRACT FROM AUTHOR]

Despite the increased frequency with which wildfire smoke now blankets portions of world, the effects of smoke on wildlife, and birds in particular, are largely unknown. We used 2 decades of banding data from the San Francisco Bay Bird Observatory to investigate how fine particulate matter (PM2.5)—a major component and indicator of wildfire smoke—influenced capture rates and body condition of 21 passerine or near-passerine bird species. Across all study species, we found a negative effect of acute PM2.5 exposure and a positive effect of chronic PM2.5 exposure on avian capture rates. Together, these findings are indicative of decreased bird activity or local site removal during acute periods of wildfire smoke, but increased activity or site colonization under chronic smoke conditions. Importantly, we also observed a negative relationship between chronic PM2.5 exposure and body mass change in individuals with multiple captures per season. Our results indicate that wildfire smoke likely influences the health and behavior of birds, ultimately contributing to a shift in activity and body condition, with differential short-term versus long-term impacts. Although more research is needed on the mechanisms driving these observed changes in bird health and behavior, as well as validation of these relationships in more areas, our results suggest that wildfire smoke is a potentially frequent large-scale environmental stressor to birds that deserves increasing attention and recognition. [ABSTRACT FROM AUTHOR]

Camera trapping is a standard tool in ecological research and wildlife conservation. Study designs, particularly for small-bodied or cryptic wildlife species often attempt to boost low detection probabilities by using non-random camera placement or baited cameras, which may bias data, or incorrectly estimate detection and occupancy. We investigated the ability of non-baited, multi-camera arrays to increase detection probabilities of wildlife. Study design components were evaluated for their influence on wildlife detectability by iteratively parsing an empirical dataset (1) by different sizes of camera arrays deployed (1-10 cameras), and (2) by total season length (1-365 days). Four species from our dataset that represented a range of body sizes and differing degrees of presumed detectability based on life history traits were investigated: white-tailed deer (Odocoileus virginianus), bobcat (Lynx rufus), raccoon (Procyon lotor), and Virginia opossum (Didelphis virginiana). For all species, increasing from a single camera to a multi-camera array significantly improved detection probability across the range of season lengths and number of study sites evaluated. The use of a two camera array increased survey detection an average of 80% (range 40-128%) from the detection probability of a single camera across the four species. Species that were detected infrequently benefited most from a multiple-camera array, where the addition of up to eight cameras produced significant increases in detectability. However, for species detected at high frequencies, single cameras produced a season-long (i.e, the length of time over which cameras are deployed and actively monitored) detectability greater than 0.75. These results highlight the need for researchers to be critical about camera trap study designs based on their intended target species, as detectability for each focal species responded differently to array size and season length. We suggest that researchers a priori identify target species for which inference will be made, and then design camera trapping studies around the most difficult to detect of those species.

Camera trapping is a standard tool in ecological research and wildlife conservation. Study designs, particularly for small-bodied or cryptic wildlife species often attempt to boost low detection probabilities by using non-random camera placement or baited cameras, which may bias data, or incorrectly estimate detection and occupancy. We investigated the ability of non-baited, multi-camera arrays to increase detection probabilities of wildlife. Study design components were evaluated for their influence on wildlife detectability by iteratively parsing an empirical dataset (1) by different sizes of camera arrays deployed (1-10 cameras), and (2) by total season length (1-365 days). Four species from our dataset that represented a range of body sizes and differing degrees of presumed detectability based on life history traits were investigated: white-tailed deer (Odocoileus virginianus), bobcat (Lynx rufus), raccoon (Procyon lotor), and Virginia opossum (Didelphis virginiana). For all species, increasing from a single camera to a multi-camera array significantly improved detection probability across the range of season lengths and number of study sites evaluated. The use of a two camera array increased survey detection an average of 80% (range 40-128%) from the detection probability of a single camera across the four species. Species that were detected infrequently benefited most from a multiple-camera array, where the addition of up to eight cameras produced significant increases in detectability. However, for species detected at high frequencies, single cameras produced a season-long (i.e, the length of time over which cameras are deployed and actively monitored) detectability greater than 0.75. These results highlight the need for researchers to be critical about camera trap study designs based on their intended target species, as detectability for each focal species responded differently to array size and season length. We suggest that researchers a priori identify target species for which inference will be made, and then design camera trapping studies around the most difficult to detect of those species.

Estimates of species richness and diversity are central to community and macroecology and are frequently used in conservation planning. Commonly used diversity metrics account for undetected species primarily by controlling for sampling effort. Yet the probability of detecting an individual can vary among species, observers, survey methods, and sites. We review emerging methods to estimate alpha, beta, gamma, and metacommunity diversity through hierarchical multispecies occupancy models (MSOMs) and multispecies abundance models (MSAMs) that explicitly incorporate observation error in the detection process for species or individuals. We examine advantages, limitations, and assumptions of these detection-based hierarchical models for estimating species diversity. Accounting for imperfect detection using these approaches has influenced conclusions of comparative community studies and creates new opportunities for testing theory.