Nucleopolyhedroviruses of forest and western tent caterpillars: cross-infectivity and evidence for activation of latent virus in high-density field populations

Abstract. 1. Cyclic population dynamics of forest caterpillars are often associated with epizootics of nucleopolyhedrovirus, but it is not known how these viruses persist between generations or through the fluctuations in host population density. 2. To explore the question of virus persistence at different phases of the population cycle, the nucleopolyhedroviruses of two species of tent caterpillar that co‐occur in British Columbia, Canada, Malacosoma californicum pluviale (western tent caterpillar) and Malacosoma disstria (forest tent caterpillar), were characterised. The cross‐infectivity of the viruses in these two host species was investigated to determine whether there might be a route for virus persistence via the alternative host species. Any virus produced in the cross‐infections was characterised to confirm true cross‐infection or to ascertain whether cross‐inoculation triggered latent virus persisting within the population. 3. The virus associated with forest tent caterpillars (MadiNPV) did not infect western tent caterpillars from low‐density populations, nor did it trigger a latent virus infection; however, inoculation of forest tent caterpillars from high‐density populations with virus from western tent caterpillars (McplNPV) resulted in viral infection, but without a dose–response relationship. 4. Analysis of DNA profiles of virus resulting from cross‐infection of the forest tent caterpillar with McplNPV, revealed that 88% of these infections were caused by MadiNPV rather than McplNPV; however the virus from all 44 infected individuals was identical and differed in DNA profile from the stock MadiNPV used for cross‐infection. This suggests strongly that forest tent caterpillars from high‐density field populations harbour a latent, persistent, or sublethal form of MadiNPV that was triggered by exposure to nucleopolyhedrovirus from the western tent caterpillar. 5. Virus was not activated in western tent caterpillars collected over 2 years of late population decline and the first year of population increase.     

Changes in the fecundity of tent caterpillars: a correlated character of disease resistance or sublethal effect of disease?

Over the fluctuation in population density of tent caterpillars, Malacosoma californicum pluviale and M. disstria, fecundity changes from being high at peak density to low for several years during the decline. During the increase phase, fecundity rapidly returns to moderately high levels with a further increase occurring to-ward the end of the increase phase. Two hypotheses which might explain these shifts are that (1) mortality from viral disease which is common during population declines selects for resistant individuals with low fecundity as an associated characteristic, and (2) sublethal viral disease reduces fecundity of moths during population decline. In this study we observed rapid shifts in the frequencies of large and small egg masses and in the mean fecundity between different phases of the population fluctuation. Viral disease was more common in caterpillars from small egg masses of the forest tent caterpillar. These observations are consistent with the hypothesis that sublethal effects of virus reduce the fecundity of moths during the population decline, but high fecundity is quickly restored when disease is rare during the population increase.     

Hierarchical spatial structure of genetically variable nucleopolyhedroviruses infecting cyclic populations of western tent caterpillars

The cyclic population dynamics of western tent caterpillars, Malacosoma californicum pluviale, are associated with epizootics of a nucleopolyhedrovirus, McplNPV. Given the dynamic fluctuations in host abundance and levels of viral infection, host resistance and virus virulence might be expected to change during different phases of the cycle. As a first step in determining if McplNPV virulence and population structure change with host density, we used restriction fragment length polymorphism (RFLP) analysis to examine the genetic diversity of McplNPV infecting western tent caterpillar populations at different spatial scales. Thirteen dominant genetic variants were identified in 39 virus isolates (individual larvae) collected from field populations during one year of low host density, and another distinct variant was discovered among nine additional isolates in two subsequent years of declining host density. The distribution of these genetic variants was not random and indicated that the McplNPV population was structured at several spatial levels. A high proportion of the variation could be explained by family grouping, which suggested that isolates collected within a family were more likely to be the same than isolates compared among populations. Additionally, virus variants from within populations (sites) were more likely to be the same than isolates collected from tent caterpillar populations on different islands. This may indicate that there is limited mixing of virus among tent caterpillar families and populations when host population density is low. Thus there is potential for the virus to become locally adapted to western tent caterpillar populations in different sites. However, no dominant genotype was observed at any site. Whether and how selection acts on the genetically diverse nucleopolyhedrovirus populations as host density changes will be investigated over the next cycle of tent caterpillar populations.     

Macrogeographic clines in fecundity, reproductive allocation, and offspring size of the forest tent caterpillar Malacosoma disstria

1. The fecundity of the forest tent caterpillar varies considerably across its geographic range. Field data indicate that populations in the southern United States (Gulf States) produce nearly twice as many eggs as females from Canada or the Lake States, with little or no difference in the size of adult females. 2. In controlled rearing experiments, female forest tent caterpillar from the southern United States (Louisiana) had much larger clutch sizes than same sized females from northern populations in Michigan or Manitoba, Canada. Increased fecundity in Louisiana females was achieved through a significant reduction in egg size and a concomitant increase in the allocation of resources to egg production. 3. Comparison of 10 forest tent caterpillar populations spanning a 27° latitudinal gradient, validated the results of detailed comparisons among the three populations above by confirming the strong negative correlation between latitude and clutch size. 4. Neonate forest tent caterpillars from Manitoba were significantly larger than larvae from either Michigan or Louisiana. Michigan larvae were intermediate in size. It is postulated that large neonates are advantageous in thermally limiting environments. More than three times as many degree‐days are available to Louisiana neonates during the first 2 weeks after hatching. A consistently favourable climate during the vulnerable post‐hatching period may have allowed the evolution of larger clutches at the expense of neonate size in southern populations.     

The effect of food limitation on immunity factors and disease resistance in the western tent caterpillar

Epizootics of nucleopolyhedrovirus characterize declines of cyclic populations of western tent caterpillars, Malacosoma pluviale californicum. In field populations, infection can be apparently lacking in one generation and high in the next. This may suggest an increase in the susceptibility to infection of larvae at peak density or the triggering of a vertically transmitted virus. Here, we test the hypothesis that reduced food availability, as may occur during population outbreaks of tent caterpillars, influences the immunocompetence of larvae and increases their susceptibility to viral infection. We compared immunity factors, hemolymph phenoloxidase and hemocyte numbers, and the susceptibility to nucleopolyhedroviral infection of fifth instar larvae that were fully or partially fed as fourth instars. To determine if maternal or transgenerational influences occurred, we also determined the susceptibility of the offspring of the treated parents to viral infection. Food limitation significantly reduced larval survival, development rate, larval and pupal mass, moth fecundity and levels of hemolymph phenoloxidase, but not the numbers of hemocytes. Neither the food-reduced larvae nor their offspring were more susceptible to viral infection and were possibly even less susceptible at intermediate viral doses. Food reduction did not activate latent or covert viral infection of larvae as might be expected as a response to stress. We conclude that reducing the food intake of fourth instar larvae to an extent that had measurable and realistic impacts on their life history characteristics was not translated into increased susceptibility to viral infection.     

Genetic Similarity of Island Populations of Tent Caterpillars during Successive Outbreaks

Cyclic or fluctuating populations experience regular periods of low population density. Genetic bottlenecks during these periods could give rise to temporal or spatial genetic differentiation of populations. High levels of movement among increasing populations, however, could ameliorate any differences and could also synchronize the dynamics of geographically separated populations. We use microsatellite markers to investigate the genetic differentiation of four island and one mainland population of western tent caterpillars, Malacosoma californicum pluviale, in two periods of peak or pre-peak density separated by 8 years. Populations showed high levels of genetic variation and little genetic differentiation either temporally between peaks or spatially among sites. Mitochondrial haplotypes were also shared between one island population and one mainland population in the two years studied. An isolation-by-distance analysis showed the F_ST values of the two geographically closest populations to have the highest level of differentiation in both years. We conclude that high levels of dispersal among populations maintain both synchrony of population dynamics and override potential genetic differentiation that might occur during population troughs. As far we are aware, this is the first time that genetic similarity between temporally separated population outbreaks in insects has been investigated. A review of genetic data for both vertebrate and invertebrate species of cyclic animals shows that a lack of spatial genetic differentiation is typical, and may result from high levels of dispersal associated with fluctuating dynamics.     

Does tent caterpillar attack reduce the food quality of red alder foliage?

Summary We assayed the quality of red alder trees for western tent caterpillar growth and survival to test the hypothesis that caterpillar feeding stimulates plant defenses in both attacked and adjacent trees. Three years of high tent caterpillar density were necessary before deterioration in foliage quality occurred, and even then only foliage from trees which were almost completely defoliated in the current year reduced the growth of caterpillars. Both tent size and mean egg mass size increased after the second year of high density which indicates that good conditions still existed for tent caterpillars after 2 to 3 years of heavy feeding.Egg masses which were moved to areas where trees had not recently supported a high caterpillar population produced significantly smaller tents than endemic controls in 1982. Therefore the small tent and egg mass size of the high density population in 1982 was inherent to the insects rather than modified by food source. In 1983 the tents from introduced egg masses were as large as naturally occurring tents.If lightly attacked trees within areas of high caterpillar density are better defended against insect attack, this does not show up in their ability to support caterpillar growth and survival. We found no evidence to support the hypothesis that trees communicate insect attack and stimulate chemical defenses in adjacent trees. Reduced foliage quality seems to be a result of extensive insect damage rather than a defense against insect damage.     

Orientation and Dispersal Patterns of the Eastern Tent Caterpillar, <Emphasis Type="Italic">Malacosoma americanum</Emphasis> F. (<Emphasis Type="Italic">Lepidoptera: Lasiocampidae</Emphasis>)

Larvae of the eastern tent caterpillar, Malacosoma americanum, undergo density-dependent dispersal in response to depleted resources. Because these caterpillars have recently been implicated in abortions of pregnant mares (equine Mare Reproductive Loss Syndrome, or MRLS), there is increased interest in managing caterpillar populations, potentially through manipulation of caterpillar dispersal behavior. Consequently, we investigated dispersal patterns of food-deprived eastern tent caterpillars in artificial arenas with respect to distance, direction, and response to visual stimuli. Distance traveled is influenced by time of day, and is strongly correlated with time elapsed. Movement is non-random, and correlates closely with the position of the sun. The pattern is more pronounced with foraging third instars than with penultimate fifth instars. Visual cues appear important in caterpillar orientation, and caterpillars are responsive to vertically oriented, black objects.     

Climate and outbreaks of the forest tent caterpillar

Some have suggested that the periodic outbreaks of the forest tent caterpillar. Malacosoma disstria are triggered by weather the temperature at the time of early larval feeding, and overwintering temperatures To assess the role of these factors, defoliation maps, compiled annually from flight surveys for the province of Ontario. were compared to similarly scaled temperature records An analysis of the year to year variation shows no relationship between the pattern of increases or declines in defoliation and either temperatures during early larval development, or overwintering temperatures Four periods of defoliation by forest tent caterpillars were observed in Ontario over 41 yr. but at individual sites extensive defoliation did not occur for each of the outbreak periods Defoliation was less severe in regions with low overwintering temperatures, but was not related to the average number of degree days m the early spring Outbreaks were most common in areas where deciduous forests were extensive, and the mean overwintering temperatures were above −40°C While these weather variables do not apparently explain the details of population dynamics of forest tent caterpillars, extreme weather conditions might synchronize populations     

Adaptation in an insect host–plant pathogen interaction

Selection on parasites to adapt to local host populations may be direct or through other components of the system such as vectors or the food plant on which the parasite is ingested. To test for local adaptation of nucleopolyhedrovirus among island populations of western tent caterpillars, Malacosoma californicum pluviale, we compared virus isolates from three geographically distinct sites with different dominant host plants. Pathogenicity, speed of kill and virus production of each isolate were examined on the three food plants. Virus isolates from the two permanent host populations had the fastest speed of kill on the host plant from which they were isolated. This was not the case for a caterpillar population that goes extinct when populations are regionally low. Virus isolates on some plant species combined rapid speed of kill with high virus yield. Infection of hosts by mixed microparasite populations could facilitate local adaptation in response to differing food plant chemistry.     

Life‐history consequences and disease resistance of western tent caterpillars in response to localised,herbivore‐induced changes in alder leaf quality

1. Plants can respond to herbivore damage with phenotypically plastic changes in quality that negatively affect herbivores and prevent subsequent attack – induced defences. 2. The present study tested whether trees respond to herbivory with localised induction, and whether life‐history traits and disease resistance of an insect herbivore are altered on induced branches of the trees. 3. The influences of localised, within‐branch, herbivore‐induced changes in red alder trees (Alnus rubra Bong.) on fitness characteristics of western tent caterpillars (Malacosoma californicum pluviale Dyar) were evaluated. In the field, randomly selected branches of trees were infested with tent caterpillar larvae and the adjacent branches were maintained as non‐infested controls. In the laboratory, larvae were fed leaves from either induced or non‐induced branches through to adult emergence. A second cohort of larvae was challenged with a viral pathogen to compare their disease susceptibility on induced versus non‐induced foliage. 4. Herbivore‐induced, localised responses of damaged branches reduced leaf quality for growth and the fecundity of female western tent caterpillars, but not that of males. Larvae fed induced leaves had a higher survival overall and a reduced mortality due to unidentified non‐viral pathogens than did their counterparts on non‐induced leaves. However, there was no influence of leaf quality on baculovirus‐induced mortality. 5. These findings suggest that localised induced changes in leaf quality could potentially influence populations of tent caterpillars in contradictory ways by reducing their growth rate and fecundity to a modest degree, while improving their survival and resistance to unidentified non‐viral pathogens to a larger extent.     

Social predation by ants as a mortality source for an arboreal gregarious forest pest

Biocontrol of caterpillars by ants is highly variable, and we investigate how the strength of the trophic relationship between ants and an important outbreaking forest pest depends on phenological synchrony and on social foraging. We test the hypothesis that early spring foraging by ants, coupled with eusocial recruitment behavior, could undermine the caterpillar's strategies to achieve either enemy-free space or predator satiation.We use a series of field surveys and experiments in trembling aspen stands (Populus tremuloides) in the boreal forest of eastern Canada to assess the role of ants in early-instar mortality of the outbreaking, gregarious forest tent caterpillar (Malacosoma disstria). We also investigate individual-level mechanisms related to phenology and social behavior that underlie the effectiveness of ants as biocontrol on caterpillars. Our results show that ants climb trees early in the spring and harvest young forest tent caterpillars, suggesting that early phenology does not provide an entirely enemy-free space for caterpillars. Our findings further show that recruitment-based social foraging enables ants to deplete groups of gregarious prey, suggesting that these eusocial insects are particularly effective at generating predation pressure on gregarious herbivores since they do not satiate easily. Finally, a manipulative predator exclusion experiment confirms that ant predation is a significant mortality source for early-instar forest tent caterpillars. Taken together, these results suggest that phenology and sociality could modulate the role of ants as effective caterpillar predators and thus showcase the importance of considering natural history and behavioral traits when studying trophic interactions and their role in population dynamics.     

Nuclear polyhedrosis virus as a biological control agent for Malacosoma americanum (Lepidoptera: Lasiocampidae)

In addition to damaging trees, the eastern tent caterpillar is implicated in early fetal loss and late‐term abortion in horses. In a field study, we evaluated the potential biological control of the caterpillar using eastern tent caterpillar nuclear polyhedrosis virus (ETNPV), a naturally occurring virus that is nearly species‐specific. Egg masses were hatched and second instar larvae were fed virus‐inoculated foliage to propagate the virus in vivo. Then, a viral pesticide was formulated at concentrations of 10⁴, 10⁶ and 10⁸ polyhedral inclusion bodies per ml. The pesticide was applied to foliage on which second, third and fourth instar caterpillars were feeding. When the majority of surviving larvae reached the sixth instar, colonies were collected and the surviving caterpillars counted. Mean numbers of surviving caterpillars per treatment were compared via 95% bootstrap confidence intervals. The data indicate second instar caterpillars were highly susceptible to the virus, but only at the highest concentration tested. Third instar caterpillars were also somewhat susceptible to high virus concentrations, while fourth instar caterpillars were fairly resistant. Our data provide the strongest evidence to date that ETNPV can be propagated, harvested and refined for formulation as a biological control agent for eastern tent caterpillar. Its use on this insect may be merited in circumstances where landowners and managers need to protect trees and horses.     

Plasticity in Forest Tent Caterpillar Collective Foraging Schedules

Self‐organization can generate synchronized group activity without external triggering cues, and schedules of self‐organized collective activity can vary with environmental conditions. This plasticity can improve group members’ ability to meet their requirements in different environments. In colonial caterpillars, synchronized colony foraging schedules have been postulated to depend either on avoidance of visual predators or on temperature effects on ectotherm physiology. We examine the foraging schedule of forest tent caterpillars (Malacosoma disstria) under different constant conditions to distinguish between these hypotheses. Plasticity in the foraging schedule was tested by keeping colonies under different constant regimes of light and temperature. Digital video and tracking software were used to record the colony's alternation between quiescent and active bouts. The duration and frequency of bouts was compared between treatments. The schedule of synchronized colony activity was not affected by lighting, but it accelerated at higher temperature, because of a decrease in the duration of both active and quiescent bouts. Forest tent caterpillars’ foraging schedule thus depends on the time required to accomplish the tasks of food finding (active bouts) and food processing (quiescent bouts). As caterpillars are ectotherms, locomotion and digestion rates increase at higher temperature and both tasks are accomplished faster. The forest tent caterpillar and the congeneric eastern tent caterpillar (M. americanum) both exhibit self‐organized synchronized collective foraging, but environmental modulation of foraging schedule differs between these species, according to differences in social organization and thermal ecology. Eastern tent caterpillars maintain a fixed foraging schedule under varying temperatures and use the tent to maintain high metabolic rates. In the forest tent caterpillar, flexibility of the foraging schedule in accordance with changes in metabolism lessens the constraints imposed by collective foraging. Synchronous foraging, where entire social groups travel together to and from feeding sites, is thought to have several fitness advantages including improved food finding, recruitment to profitable food sources, anti‐predator defense and group thermoregulation between foraging expeditions.     

Breeding success and lutein availability in great tit (Parus major)

The relationship among temporal variation in the availability of carotenoid-rich food, tissue carotenoid levels and breeding success are poorly known. We studied how diet quality and quantity affect the carotenoid profile and fledging success of great tit (Parus major) nestlings along a pollution gradient. We found declining seasonal trend in lutein concentration of caterpillars, which may be the explanation for the declining trend in nestlings' lutein concentration of plasma with season, despite the increase in caterpillar biomass. This may be because the biomass of most lutein-rich caterpillars (autumnal moths) decreased and less lutein-rich caterpillars (sawflies) increased during the breeding season. The temporal difference in occurrence of different caterpillar species means that peak lutein availability does not coincide with peak caterpillar abundance. However the positive association between total larval biomass and the number of great tit fledglings may suggest that fledging success depends more on total caterpillar availability than on lutein concentration of caterpillars.     

松树受害后一些化学物质含量的变化及其对马尾松毛虫种群参数的影响

通过探讨松树受害后松针的一些化学物质变化与马尾松毛虫Dendrolimus punctatus 种群参数的相互作用关系。结果表明：松针被马尾松毛虫为害后,针叶的氨基酸含量减少、单宁和总酚含量增加;马尾松毛虫取食被害松针后,体内的2种解毒酶(过氧化氢酶、羧酸酯酶)活性增加,其种群参数表现出发育历期延长、体重减轻、死亡率增加、生殖力下降的变 化。     

The microbiome of the Melitaea cinxia butterfly shows marked variation but is only little explained by the traits of the butterfly or its host plant

Understanding of the ecological factors that shape intraspecific variation of insect microbiota in natural populations is relatively poor. In Lepidopteran caterpillars, microbiota is assumed to be mainly composed of transient bacterial symbionts acquired from the host plant. We sampled Glanville fritillary (Melitaea cinxia) caterpillars from natural populations to describe their gut microbiome and to identify potential ecological factors that determine its structure. Our results demonstrate high variability of microbiota composition even among caterpillars that shared the same host plant individual and most likely the same genetic background. We observed that the caterpillars harboured microbial classes that varied among individuals and alternated between two distinct communities (one composed of mainly Enterobacteriaceae and another with more variable microbiota community). Even though the general structure of the microbiota was not attributed to the measured ecological factors, we found that phylogenetically similar microbiota showed corresponding responses to the sex and the parasitoid infection of the caterpillar and to those of the host plant's microbial and chemical composition. Our results indicate high among-individual variability in the microbiota of the M. cinxia caterpillar and contradict previous findings that the host plant is the major driver of the microbiota communities of insect herbivores.     

Diet flexibility in a declining long‐distance migrant may allow it to escape the consequences of phenological mismatch with its caterpillar food supply

Climate‐driven shifts in prey phenology may lead to asynchrony with the timing of peak resource requirements of their predators, leading to a reduction in productivity and population declines. Migrant species that cannot adjust their arrival times may be particularly at risk, especially those that breed in seasonal environments and for which a temporarily super‐abundant prey source is important, such as insectivorous passerine birds that take advantage of the seasonal flush of caterpillars to feed their young. We assess whether population declines of the trans‐Saharan migratory Wood Warbler Phylloscopus sibilatrix are likely to have been caused by phenological mismatch. We measured seasonal invertebrate biomass and various fitness parameters, including the timing of breeding and breeding success, in two time periods: 1982–1984, prior to the species’ decline in the UK, and 2009–2011, as the reduction in numbers continued. Although birds bred on average a week earlier in 2009–2011 than in 1982–1984, this was not adequate to track the more rapid advancement of peak caterpillar biomass, which advanced by 12 days and was closely correlated with spring temperatures. Moreover, although caterpillars were the dominant prey fed to nestlings, there was only limited evidence that productivity was positively related to caterpillar biomass in the environment. Considering only successful nests, synchrony with the food peak did not produce heavier nestlings and had only a small positive effect on fledging success, although there was a seasonal decline in productivity when all nests were considered. We conclude that the lack of a marked effect of the observed mismatch is due to Wood Warblers’ generalist diet, enabling them to breed successfully on prey other than caterpillars. Although other studies have demonstrated that climate‐driven asynchrony of predator and prey populations can have impacts on avian demography, this study highlights the importance of investigating the generality of those findings.     

High genetic diversity in the blue-listed British Columbia population of the purple martin maintained by multiple sources of immigrants

To assess genetic diversity in the blue-listed purple martin (Progne subis) population in British Columbia, we analysed mitochondrial control region sequences of 93 individuals from British Columbia and 121 individuals collected from seven localities of the western and eastern North American subspecies P. s. arboricola and P. s. subis, respectively. Of the 47 haplotypes we detected, 34 were found exclusively in western populations, and 12 were found only in eastern populations. The most common eastern haplotype (25) was also found in three nestlings in British Columbia and one in Washington. Another British Columbia nestling had a haplotype (35) that differed by a C to T transition from haplotype 25. Coalescent analysis indicated that these five nestlings are probably descendents of recent immigrants dispersing from east to the west, because populations were estimated to have diverged about 200,000–400,000 ybp, making ancestral polymorphism a less likely explanation. Maximum likelihood estimates of gene flow among all populations detected asymmetrical gene flow into British Columbia not only of rare migrants from the eastern subspecies in Alberta but also a substantial number of migrants from the adjacent Washington population, and progressively lower numbers from Oregon in an isolation-by distance pattern. The influx of migrants from different populations is consistent with the migrant-pool model of recolonization which has maintained high genetic diversity in the small recovering population in British Columbia. Thus, the risk to this population is not from genetic erosion or inbreeding following a severe population crash, but from demographic stochasticity and extinction in small populations.     

Identification of metapopulation dynamics among Northern Goshawks of the Alexander Archipelago, Alaska, and Coastal British Columbia

Northern Goshawks occupying the Alexander Archipelago, Alaska, and coastal British Columbia nest primarily in old-growth and mature forest, which results in spatial heterogeneity in the distribution of individuals across the landscape. We used microsatellite and mitochondrial data to infer genetic structure, gene flow, and fluctuations in population demography through evolutionary time. Patterns in the genetic signatures were used to assess predictions associated with the three population models: panmixia, metapopulation, and isolated populations. Population genetic structure was observed along with asymmetry in gene flow estimates that changed directionality at different temporal scales, consistent with metapopulation model predictions. Therefore, Northern Goshawk assemblages located in the Alexander Archipelago and coastal British Columbia interact through a metapopulation framework, though they may not fit the classic model of a metapopulation. Long-term population sources (coastal mainland British Columbia) and sinks (Revillagigedo and Vancouver islands) were identified. However, there was no trend through evolutionary time in the directionality of dispersal among the remaining assemblages, suggestive of a rescue–effect dynamic. Admiralty, Douglas, and Chichagof island complex appears to be an evolutionarily recent source population in the Alexander Archipelago. In addition, Kupreanof island complex and Kispiox Forest District populations have high dispersal rates to populations in close geographic proximity and potentially serve as local source populations. Metapopulation dynamics occurring in the Alexander Archipelago and coastal British Columbia by Northern Goshawks highlight the importance of both occupied and unoccupied habitats to long-term population persistence of goshawks in this region.