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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.

Dispersal of whitebark pine (Pinus albicaulis Engelm.), a keystone species of many high-elevation ecosystems in western North America, depends on Clark’s nutcracker (Nucifraga columbiana Wilson), a seed-caching bird with an affinity for whitebark seeds. To the extent that this dependence is mutual, declines in whitebark seed production could cause declines in nutcracker abundance. Whitebark pine is in decline across much of its range due to interacting stressors, including the non-native pathogen white pine blister rust (Cronartium ribicola J. C. Fisch.). We used avian point-count data and tree surveys from four national park units to investigate whether trends in whitebark pine can explain trends in Clark’s nutcracker. Spatial trends were modeled using recent data from two parks, while temporal trends were modeled using longer time-series of nutcracker and whitebark data from two additional parks. To assess the potential dependence of nutcrackers on whitebark, we linked a model of nutcracker density (accounting for detection probability) with a model of whitebark trends, using a Bayesian framework to translate uncertainty in whitebark metrics to uncertainty in nutcracker density. In Mount Rainier National Park, temporal models showed dramatic declines in nutcracker density concurrent with significant increases in whitebark crown mortality and trees infected with white pine blister rust. However, nutcrackers did not trend with whitebark metrics in North Cascades National Park Service Complex. In spatial models of data from Yosemite National Park and Sequoia-Kings Canyon National Park, nutcracker density varied not only with local cover of whitebark but also with elevation and, in Sequoia-Kings Canyon, with cover of another species of white pine. Our results add support for the hypothesis that the mutualism between whitebark pine and Clark’s nutcracker is vulnerable to disruption by blister rust, and our approach integrates data across monitoring programs to explore trends in species interactions.

Population age structure is important for understanding population dynamics, but can be difficult to resolve in landbirds due to the limited number of age classes discernible by examining plumage. In forests of western North America, Black-backed Woodpeckers (Picoides articus) typically colonize burned areas shortly after fire, but densities decline within 6–10 yr. This pattern is often assumed to result from adult Black-backed Woodpeckers abandoning territories when food resources wane, yet long-distance breeding dispersal is relatively rare in birds, whereas long-distance natal dispersal is more common. To determine whether colonization of newly burned areas is driven primarily by breeding dispersal of adults or natal dispersal by young birds, we captured 57 adult Black-backed Woodpeckers in 6 burned areas in California between 1 and 8 yr after fire. We used patterns of multiple feather generations retained among primary coverts, secondaries, and secondary coverts to assign birds to 1 of 5 age classes (second-, third-, and fourth-calendar-year; after-third-calendar-year; and after-fourth-calendar-year). Population age structure varied dramatically across burned areas, with a preponderance of second-calendar-year birds in the 1 yr and 2 yr postfire areas, and a preponderance of birds at least 3 yr old in the older postfire areas. Poisson generalized linear mixed models (GLMMs) revealed that the effect of years since fire on woodpecker age was highly significant (z = 3.575, P < 0.001). Our results indicate that natal dispersal is the primary means by which Black-backed Woodpeckers colonize recently burned areas in western forests, and that breeding dispersal is uncommon. The decline of Black-backed Woodpecker populations 6–10 yr after fire likely reflects the lifespan of individual birds that colonized the burned area, or of offspring that they produced in the early postfire years. Our discrimination of Black-backed Woodpeckers into 5 age classes confirms previous suppositions about plumage-based age determination in woodpeckers, and is likely applicable to other woodpecker species.

An emerging hypothesis in fire ecology is that pyrodiversity increases species diversity. We test whether pyrodiversity—defined as the standard deviation of fire severity—increases avian biodiversity at two spatial scales, and whether and how this relationship may change in the decade following fire. We use a dynamic Bayesian community model applied to a multi-year dataset of bird surveys at 1106 points sampled across 97 fires in montane California. Our results provide strong support for a positive relationship between pyrodiversity and bird diversity. This relationship interacts with time since fire, with pyrodiversity having a greater effect on biodiversity at 10 years post-fire than at 1 year post-fire. Immediately after fires, patches of differing burn severities hold similar bird communities, but over the ensuing decade, bird assemblages within patches of contrasting severities differentiate. When evaluated at the scale of individual fires, fires with a greater heterogeneity of burn severities hold substantially more species. High spatial heterogeneity in severity, sometimes called ‘mixed-severity fire', is a natural part of wildfire regimes in western North America, but may be jeopardized by climate change and a legacy of fire suppression. Forest management that encourages mixed-severity fire may be critical for sustaining biodiversity across fire-prone landscapes.

Variation in fire characteristics, termed pyrodiversity, plays an important role in structuring post‐fire communities, but little is known about the importance of pyrodiversity for individual species. The availability of diverse post‐fire habitats may be key for fire‐associated species if they require different resources at different life‐history stages. We tested for age‐specific habitat relationships in the black‐backed woodpecker, a post‐fire specialist. We used radio‐telemetry to track fledgling and adult woodpeckers in burned forests and built resource selection functions to compare the effect of stand‐, tree‐ and snag‐level covariates between adults and fledglings. Fledgling black‐backed woodpeckers selected habitat with more live trees than adults and used more heterogeneous habitats burned at lower severity, illustrating strong age‐dependent effects on habitat selection. Within selected stands, fledglings were less likely to use snags and more likely to use live trees when compared to adults, but both age classes showed strong positive selection for larger‐diameter trees (live and dead). Over the 60 days after leaving their nests, fledglings showed an increasing propensity to use snags rather than live trees. Our results provide evidence that the predation–starvation hypothesis, which posits a trade‐off between foraging efficiency and the need to minimise predation risk, plays a role in structuring the age‐dependent habitat use of a burned forest specialist. Adult black‐backed woodpeckers selected resources associated with food availability, but these resources occurred in relatively open, exposed habitat. Fledglings selected habitat that provided increased cover, perhaps as a strategy to reduce predation risk. Synthesis and applications. Globally, fires are increasing in severity and extent, leading to increased focus on fire‐associated species that play keystone roles in facilitating biodiversity resilience. Our findings suggest that a diversity of patches burned at different severities may benefit post‐fire specialists like the black‐backed woodpecker at multiple life‐history stages. The increasing prevalence of large, homogeneously high‐severity ‘megafires’ may present an emerging threat even to post‐fire specialists, and we urge land managers to consider opportunities to promote pyrodiversity in the face of novel fire regimes. Globally, fires are increasing in severity and extent, leading to increased focus on fire‐associated species that play keystone roles in facilitating biodiversity resilience. Our findings suggest that a diversity of patches burned at different severities may benefit post‐fire specialists like the black‐backed woodpecker at multiple life‐history stages. The increasing prevalence of large, homogeneously high‐severity ‘megafires’ may present an emerging threat even to post‐fire specialists, and we urge land managers to consider opportunities to promote pyrodiversity in the face of novel fire regimes.

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.

Monitoring species in National Parks facilitates inference regarding effects of climate change on population dynamics because parks are relatively unaffected by other forms of anthropogenic disturbance. Even at early points in a monitoring program, identifying climate covariates of population density can suggest vulnerabilities to future change. Monitoring landbird populations in parks during the breeding season brings the added benefit of allowing a comparative approach to inference across a large suite of species with diverse requirements. For example, comparing resident and migratory species that vary in exposure to non‐park habitats can reveal the relative importance of park effects, such as those related to local climate. We monitored landbirds using breeding‐season point‐count data collected during 2005–2014 in three wilderness areas of the Pacific Northwest (Mount Rainier, North Cascades, and Olympic National Parks). For 39 species, we estimated recent trends in population density while accounting for individual detection probability using Bayesian hierarchical N‐mixture models. Our analyses integrated several recent developments in N‐mixture modeling, incorporating interval and distance sampling to estimate distinct components of detection probability while also accommodating count intervals of varying duration, annual variation in the length and number of point‐count transects, spatial autocorrelation, random effects, and covariates of detection and density. As covariates of density, we considered metrics of precipitation and temperature hypothesized to affect breeding success. We also considered effects of park and elevational stratum on trend. Regardless of model structure, we estimated stable or increasing densities during 2005–2014 for most populations. Mean trends across species were positive for migrants in every park and for residents in one park. A recent snowfall deficit in this region might have contributed to the positive trend, because population density varied inversely with precipitation‐as‐snow for both migrants and residents. Densities varied directly but much more weakly with mean spring temperature. Our approach exemplifies an analytical framework for estimating trends from point‐count data, and for assessing the role of climatic and other spatiotemporal variables in driving those trends. Understanding population trends and the factors that drive them is critical for adaptive management and resource stewardship in the context of climate change.

1. Fire creates challenges and opportunities for wildlife through rapid destruction, modification and creation of habitat. Fire has spatially variable effects on landscapes; however, for species that benefit from the ephemeral resource patches created by fire, it is critical to understand characteristics of fires that promote postfire colonization and persistence and the spatial scales on which they operate. 2. Using a model postfire specialist, the black-backed woodpecker (Picoides arcticus), we examined how colonization and persistence varied across two spatial scales as a function of four characteristics of fire regimes—fire severity, fire size, fire ignition date and number of years since fire. 3. We modelled black-backed woodpecker colonization and persistence using data from 108 recently burned forests in the Sierra Nevada and southern Cascades ecoregions of California, USA, that we monitored for up to 10 years following fire. We employed a novel, spatially hierarchical, dynamic occupancy framework which differentiates colonization and persistence at two spatial scales: across fires and within fires. 4. We found strong effects of fire characteristics on dynamic rates, with colonization and persistence declining across both spatial scales with increasing years since fire. Additionally, at sites within fires, colonization decreased with fire size and increased with fire severity and for fires with later ignition dates. 5. Our results support the notion that different aspects of a species' environment are important for population processes at different spatial scales. As habitat quality is ephemeral for any given postfire area, our results illustrate the importance of time since fire in structuring occupancy at the fire level, with other characteristics of fires playing larger roles in determining abundance within individual fires. Our results contribute to the broader understanding of how variation in fire characteristics influences the colonization and persistence of species using ephemeral habitats, which is necessary for conserving and promoting postfire biodiversity in the context of rapidly shifting fire regimes.

Background Fire can impact ecosystems and species over both short and long timeframes, resulting in pervasive impacts on the structure of avian communities. While recent research has highlighted the strong impact of fire on bird communities in the short term, there remains a need for understanding long-term population processes following fire, particularly in forested landscapes that are burning more frequently than in the past century. We analyzed avian response to fire using point-count data from 1999–2019 within national parks of the Sierra Nevada Inventory & Monitoring Network, combined with high-resolution estimates of burn severity from fires that burned up to 35 years prior to each count. We used a hierarchical Bayesian framework to account for imperfect detection of birds while estimating the potentially divergent effects of fire on population density over time for each of 42 species. Our models integrated time-varying data on habitat characteristics that would otherwise be confounded with fire history, such as canopy cover and height. Results In aggregate, bird population density increased rapidly after fire and remained higher in burned areas for at least 35 years relative to unburned areas. Moderate-severity burns typically resulted in more immediate and enduring positive effects than burns of lower severity. Of 42 bird species analyzed, only 13 showed little response to fire, eight responded positively for less than 20 years, 10 showed responses (nine positive) persisting longer than 20 years, and 11 showed positive responses with little or no sign of attenuation even 35 years after a fire. Responses did not align with broad migratory, nesting or foraging traits. Conclusions A wide variety of birds appeared to benefit—immediately or eventually—from burns at bird point-count stations in two fire-prone parks of the Sierra Nevada. These results offer a rare perspective on long-term avian response to fire and postfire successional processes, in some of the few western forests where effects of fire are relatively unconfounded by anthropogenic habitat loss and resource extraction.

Provisioning behavior can have cascading effects on nest survival, juvenile recruitment, and parental fitness. Provisioning behavior may be influenced by temporal variables, such as nestling age, or habitat variables, such as food availability and landscape disturbance. Black-backed Woodpeckers (Picoides arcticus) are associated with burned forests, where they nest in stands of fire-killed trees. Our objectives were to determine if their nestling provisioning behavior is influenced by the characteristics of fires and post-fire management, and if provisioning behavior differs with sex and varies across the breeding season. We recorded provisioning rates and the size of prey deliveries at 21 nests of Black-backed Woodpeckers in a burned area of northern California in 2014–2015 and examined the possible effects of habitat, temporal variables, and parental sex on provisioning rates and prey delivery size using mixed-effects models. Provisioning rates were higher for early season nests than late-season nests, and provisioning rates increased with nestling age. The size of prey provided to nestlings increased with nestling age, and prey delivery size was also larger for nests near areas where post-fire logging had occurred. Parental sex had no effect on either provisioning rates or prey delivery size. Our results suggest that, in burned forests in our study area, Black-backed Woodpeckers provisioning nestlings respond more strongly to temporal variables than habitat variables, and both sexes contribute equally to feeding young. Temporal variation in provisioning rates and prey delivery size likely reflect variation in the energetic demands of nestlings. El comportamiento de aprovisionamiento puede tener un efecto cascada sobre la supervivencia de los nidos, reclutamiento de los juveniles y aptitud de los parentales. El comportamiento de aprovisionamiento puede estar influenciado por variables temporales, como la edad de los pichones, o variables del hábitat, como la disponibilidad de alimento y el disturbio en el paisaje. Picoides arcticus están asociados a bosques propensos a incendios, donde los nidos son ubicados en arboles afectados por el fuego. Nuestros objetivos fueron los de determinar si el comportamiento de aprovisionamiento de los pichones esta influenciado por las características de los incendios y el manejo posterior al incendio, y si el comportamiento de aprovisionamiento difiere con el sexo y varia a través de la temporada de reproducción. Colectamos información sobre tasas de aprovisionamiento y el tamaño de las presas entregadas en 21 nidos de Picoides arcticus en un área incendiada del norte de California en 2014–2015 y examinamos los posibles efectos del hábitat, las variables temporales y el comportamiento parental de cada sexo sobre las tasas de aprovisionamiento y el tamaño de las presas entregadas usando modelos de efectos mixtos. Las tasas de aprovisionamiento fueron mayores para nidos construidos temprano en la temporada que en nidos construidos tarde en la temporada, y las tasas de aprovisionamiento incrementaron con la edad de los pichones. El tamaño de la presa entregado a los pichones incrementócon la edad de los pichones, y el tamaño de la presa entregada también fue mayor para nidos cerca de áreas donde existió tala posterior al incendio. Nuestro resultados sugieren que en bosques incendiados, en nuestra área de estudio, el aprovisionamiento de pichones en Picoides arcticus responde más fuertemente a variables temporales que a variables de hábitat, y que ambos sexos contribuyen igualmente a la alimentación de los polluelos. La variación temporal en tasas de aprovisionamiento y el tamaño de presa entregada posiblemente refleja la variación en las demandas energéticas de los pichones.