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A Growing Conspiracy: Recolonization of Common Ravens (Corvus corax) in Central and Southern Appalachia, USA
Abstract
Corvus corax (Common Raven, hereafter Raven) was historically ubiquitous throughout much of North America, but persecution and habitat loss after European settlement resulted in range reduction and population decline across much of the eastern US. Increasing numbers of confirmed sightings of Ravens in the eastern US over the past 70 years suggest rapid regional recolonization, particularly in central and southern Appalachia where, in many states, Ravens were thought to be extirpated or at least highly range-restricted. We compiled 64,611 Raven observations from multiple public and private sources across Appalachia between 1950 and 2016 and performed spatial analyses to characterize regional recolonization trends. The Appalachian Mountain range has served as both a refugium for Ravens during the late 19th and early 20th centuries and a regional source population for range expansion between 1950 and 2016. Ravens are now common in the mountainous areas of Appalachia and have recently expanded their range into lower elevations, including the successful recolonization of 4 states: Alabama, Kentucky, Ohio, and Tennessee. Spatial analyses demonstrated a 40% increase in the Raven’s apparent geographic range in central and southern Appalachia, which now spans at least 470,380 km2. We present an updated map detailing current Raven distributions in central and southern Appalachia and review potential habitat, interspecific, and trophic factors aiding range expansion for Ravens.
... Although common in the western United States, raven populations across the eastern United States had dwindled by the early to mid-20th century, and ravens in the Appalachian Mountains were restricted to remote refugia, often at high elevations (Harlow, 1922;Hooper, 1977). During the latter half of the 20th century, the raven's geographic range in the eastern United States expanded, and ravens in the Central and Southern Appalachians became increasingly common (Boarman & Heinrich, 2020;Hackworth et al., 2019). Recovery has been attributed to enforcement of wildlife protection mandates, forest regeneration, increased availability of carrion sources arising from the recovery of white-tailed deer (Odocoileus virginianus, Zimmermann) populations across the eastern United States and introduction of elk (Cervus canadensis, Erxleben) in some areas, and the decline in the popularity of hunting American crow (Boarman & Heinrich, 2020;Cox et al., 2003;Hackworth et al., 2019). ...
... During the latter half of the 20th century, the raven's geographic range in the eastern United States expanded, and ravens in the Central and Southern Appalachians became increasingly common (Boarman & Heinrich, 2020;Hackworth et al., 2019). Recovery has been attributed to enforcement of wildlife protection mandates, forest regeneration, increased availability of carrion sources arising from the recovery of white-tailed deer (Odocoileus virginianus, Zimmermann) populations across the eastern United States and introduction of elk (Cervus canadensis, Erxleben) in some areas, and the decline in the popularity of hunting American crow (Boarman & Heinrich, 2020;Cox et al., 2003;Hackworth et al., 2019). Although raven populations have increased in recent decades, the species remains patchily distributed across the eastern United States and rare or absent in many localities. ...
Common ravens (Corvus corax) inhabited much of the eastern United States prior to European colonization but were nearly extirpated by the mid‐1900s. Although remnant raven populations have since begun recolonizing portions of their historic range in the eastern United States, the extent of recovery remains largely unknown because of the species' elusive behavior. To aid development of targeted monitoring programs for this rare and cryptic species, we investigated factors that may influence detectability of ravens in natural cliff habitat during the nesting season in the Central Appalachian Mountains. Using a time‐to‐detection framework, we performed surveys at cliff sites with positive raven occupancy and recorded time to first detection (TFD) and confirmed cliff occupancy (i.e., occupied detection) to estimate detection probability curves as a function of survey time. We further compared multiscale habitat features of occupied and unoccupied cliff sites to characterize regional nesting habitat. Mean TFD at occupied cliffs was 14 ± 2 (SE) min. The TFD and subsequent detection probability increased with warming temperatures, likely as a result of heightened activity at nests as the reproductive season progressed. Shorter distances from observation point to the surveyed cliff resulted in longer TFD, indicating that ravens are likely sensitive to disturbance at nest sites. Analysis of cliff‐nesting habitat data identified raven selection of cliffs with large, exposed faces positioned on predominant west‐facing aspects. Mean detection probability calculated from detectability curves was ≥0.8 after the first 30 min. Using a probability‐based model and empirical detection probabilities, we estimated that raven absence from a cliff site during the nesting season may be inferred with p = 0.99 after three independent 30‐min surveys. Although ravens have been considered elusive and rare in the eastern United States, we find that their detectability at occupied cliff sites during the nesting season is relatively high and that observation of distributional changes may be easier for this species than for other, more cryptic birds.
... However, only 2 of the 44 species documented in downtown Rockingham during winter 2021-2022 have shifted their winter ranges to include Rockingham. The Fish Crow and Common Raven have had regional range expansions (Hackworth et al. 2019, LeGrand et al. 2023, McNair 1987, Seriff 2018) that have reached Rockingham. These now sympatric large-bodied omnivores have become uncommon during winter, over the past 3 decades for Fish Crow and since 2018 for Common Raven (3 spring records of 1-2 birds in late April of 2018April of , 2021April of , and 2022D.B. ...
I conducted a winter bird population study (WBPS) in a commercial district of downtown Rockingham, NC. I recorded 44 avian species (40 native suburban adapters, 4 exotic urban invaders) over 10 surveys conducted 20 December 2021 to 19 January 2022 within a 42.4-ha plot containing 25 city blocks. Thirty-one species (including all exotic urban invaders) were residents (74% of observations), whereas 13 native species were winter visitors (26%). Average winter bird species richness was 22.8 and average abundance was 143.5/40 ha. The median difference in species richness and abundance of suburban adapters was greater than exotic urban invaders among all 25 blocks, except species richness in 1 block and abundance in 4 blocks. A vegetation index (measure of the amount of vegetation) was a positive predictor of species richness for all suburban adapters and abundance for 3 species of suburban adapters (Mimus polyglottos [Northern Mockingbird], Cardinalis cardinalis [Northern Cardinal], Thryothorus ludovicianus [Carolina Wren]). Building area was a negative predictor of species richness for all suburban adapters and abundance for Northern Mockingbird. Average abundance was lower than the number of blocks in which each species was detected, except for the 3 most abundant birds (Passer domesticus [House Sparrow], Sturnus vulgaris [European Starling], Zonotrichia albicollis [White-throated Sparrow]) and Bombycilla cedrorum (Cedar Waxwing), all flocking species. Two exotic urban invaders (House Sparrow, European Starling) and 4 suburban adapters (Northern Mockingbird, Northern Cardinal, Carolina Wren, Zenaida macroura [Mourning Dove]) were also among the most abundant species (i.e., those whose average counts were ≥5 birds) and were resident species that nested within the plot the previous breeding season. The degree of compositional change of the avian community during early winter 2021-2022 compared to the last 3 decades was low in downtown Rockingham, NC.
... [20], but PA is generally less common in CS data. The recent development of statistical techniques to estimate occupancy, especially those that account for imperfect detection, has contributed to the increasing use of PA data to infer the spatial distribution of species [79,83,84]. Hence, this development would explain the increasing use of PA data obtained from CS databases. ...
Wetlands are highly threatened ecosystems, especially in boreal landscapes. They provide valuable ecological services and serve as important habitats for many species. In northern Canada, wetlands are being transformed by natural disturbances, climate change, and human activities. These changes can lead to habitat loss for species dependent on wetlands. Small wetlands, particularly ponds, are crucial for amphibians, birds, and mammals. However, there is limited knowledge about vertebrate presence in small ponds. This thesis aimed to compare peatland ponds and beaver ponds and understand the influence of habitat factors and species interactions on amphibians, birds, and mammals. The research highlighted the importance of both pond types but suggested that beaver ponds are more productive for amphibians. Birds responded differently to the two pond types, with beaver ponds supporting greater species richness. The presence of red squirrels negatively affected bird species richness. Camera trap surveys revealed unexpected preferences of certain mammals and bird species for peatland ponds. Overall, understanding wetland ecosystems is vital for their conservation and the diverse range of species they support.
The traditional regional focus of evolutionary anthropology—typically defined as places where hominin fossils, nonhuman primates, and non‐western populations reside—forms the basis of much evolutionary anthropological research. Using the highly biodiverse temperate region of Appalachia as an example, we suggest that evolutionary anthropologists have much to gain by stepping outside of this traditional geographic area. Being purposely provocative, we argue that evolutionary anthropologists might also benefit from conducting research in Appalachia and other temperate ecosystems. We briefly discuss multiple areas of study—including studies of seed dispersal, functional redundancy, convergent evolution, human behavioral ecology, and conservation—and how they can be considered within the purview of integrative and evolutionary anthropology. We also highlight broader impacts to higher education that evolutionary anthropologists can help promote by working in local ecosystems.
Surface mining for coal has taken place in the Central Appalachian region of the United States for well over a century, with a notable increase since the 1970s. Researchers have quantified the ecosystem and health impacts stemming from mining, relying in part on a geospatial dataset defining surface mining’s extent at a decadal interval. This dataset, however, does not deliver the temporal resolution necessary to support research that could establish causal links between mining activity and environmental or public health and safety outcomes, nor has it been updated since 2005. Here we use Google Earth Engine and Landsat imagery to map the yearly extent of surface coal mining in Central Appalachia from 1985 through 2015, making our processing models and output data publicly available. We find that 2,900 km² of land has been newly mined over this 31-year period. Adding this more-recent mining to surface mines constructed prior to 1985, we calculate a cumulative mining footprint of 5,900 km². Over the study period, correlating active mine area with historical surface mine coal production shows that each metric ton of coal is associated with 12 m² of actively mined land. Our automated, open-source model can be regularly updated as new surface mining occurs in the region and can be refined to capture mining reclamation activity into the future. We freely and openly offer the data for use in a range of environmental, health, and economic studies; moreover, we demonstrate the capability of using tools like Earth Engine to analyze years of remotely sensed imagery over spatially large areas to quantify land use change.
We analyze a radius bone fragment of a raven (Corvus corax) from Zaskalnaya VI rock shelter, Crimea. The object bears seven notches and comes from an archaeological level attributed to a Micoquian industry dated to between 38 and 43 cal kyr BP. Our study aims to examine the degree of regularity and intentionality of this set of notches through their technological and morphometric analysis, complemented by comparative experimental work. Microscopic analysis of the notches indicate that they were produced by the to-and-fro movement of a lithic cutting edge and that two notches were added to fill in the gap left between previously cut notches, probably to increase the visual consistency of the pattern. Multivariate analysis of morphometric data recorded on the archaeological notches and sets of notches cut by nine modern experimenters on radii of domestic turkeys shows that the variations recorded on the Zaskalnaya set are comparable to experimental sets made with the aim of producing similar, parallel, equidistant notches. Identification of the Weber Fraction, the constant that accounts for error in human perception, for equidistant notches cut on bone rods and its application to the Zaskalnaya set of notches and thirty-six sets of notches incised on seventeen Upper Palaeolithic bone objects from seven sites indicate that the Zaskalnaya set falls within the range of variation of regularly spaced experimental and Upper Palaeolithic sets of notches. This suggests that even if the production of the notches may have had a utilitarian reason the notches were made with the goal of producing a visually consistent pattern. This object represents the first instance of a bird bone from a Neanderthal site bearing modifications that cannot be explained as the result of butchery activities and for which a symbolic argument can be built on direct rather than circumstantial evidence.
In 1997, the Kentucky Department of Fish and Wildlife Resources began a restoration program intended to translocate 200 elk Cervus elaphus nelsoni per year over a nine-year period. Initially, the age structure of males in this restored elk population was heavily skewed toward the yearling age class. We examined the reproductive performance of this elk herd for two years. During 1998, the male:adult female ratio was 35:65 (corresponding to 54: 100). In 1999, the male:adult female ratio was 45:62 (corresponding to 73: 100). The proportion of yearling males declined from 89% in 1998 to 31% in 1999. We used radio telemetry to locate males and females during the rut and to document calf production. Calving rates during 1998 and 1999 were 53 and 92%, respectively. Post-release movements of adult cows (N = 22) to areas devoid of males averaged 21 km and ranged within 7-57 km. Temporary Allee effects may have been responsible for annual differences in calving rates. The calving season was 67 days when breeding was dominated by yearlings and 37 days when breeding was dominated by adults. A male age structure heavily skewed toward yearlings does not appear to limit population growth. Calving rates could be improved by reducing initial post-release wanderings of adult females. Distribution of potential mates may be more important to population growth rather than balanced sex ratios and age structures.
Throughout the ages birds have played a prominent role in the life of the people occupying the Eastern Mediterranean Basin. Because of their importance as food sources, agricultural pests, domestic pets, as well as inspirations for various art forms, they figure prominently in historical texts, fables and the public lore of these civilizations. Corvids, the bird group containing crows, ravens and magpies, is of particular importance because of the large size, conspicuous presence and significant potential for agricultural damage that these birds exhibit. The present paper was written to complete the study of this group of birds, as they appear in civilizations of Egypt, Greece and Italy.
Predation by coyotes (Canis latrans) on white-tailed deer (Odocoileus virginianus) neonates has led to reduced recruitment in many deer populations in southeastern North America. This low recruitment combined with liberal antlerless deer harvest has resulted in declines in some deer populations, and consequently, increased interest in coyote population control. We investigated whether neonate survival increased after coyote removal, whether coyote predation on neonates was additive to other mortality sources, and whether understory vegetation density affected neonate survival. We monitored neonate survival for 4 years prior to (2006–2009) and 3 years during (2010–2012) intensive coyote removal on 3 32-km2 units on the United States Department of Energy's Savannah River Site, South Carolina. We removed 474 coyotes (1.63 coyotes/km2 per unit per year), reducing coyote abundance by 78% from pre-removal levels. The best model (wi = 0.927) describing survival probability among 216 radio-collared neonates included a within-year quadratic time trend variable, date of birth, removal treatment, and a varying removal year effect. Under this model, survival differed between pre-treatment and removal periods and it differed among years during the removal period, being >100% greater than pre-treatment survival (0.228) during the first removal year (0.513), similar to pre-treatment survival during the second removal year (0.202), and intermediate during the third removal year (0.431). Despite an initial increase, the overall effect of coyote removal on neonate survival was modest. Mortality rate attributable to coyote predation was lowest during the first removal year (0.357) when survival was greatest, but the mortality rate from all other causes did not differ between the pre-treatment period and any year during removals, indicating that coyote predation acted as an additive source of mortality. Survival probability was not related to vegetation cover, either directly or in interaction with coyote abundance. When the objective is to increase the recruitment of white-tailed deer, we conclude that neither coyote control nor vegetation management appear effective. Reduction of the antlerless harvest may be necessary to meet this objective, but this harvest strategy warrants additional research in Southeastern deer populations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
We used an individual-based population model to perform a viability analysis to simulate population growth (λ) of 167 elk (Cervus elaphus manitobensis; 71 male and 96 female) released in the Cumberland Mountains, Tennessee, to estimate sustainability (i.e., λ > 1.0) and identify the most appropriate options for managing elk restoration. We transported elk from Elk Island National Park, Alberta, Canada, and from Land Between the Lakes, Kentucky, and reintroduced them beginning in December 2000 and ending in February 2003. We estimated annual survival rates for 156 radio-collared elk from December 2000 until November 2004. We used data from a nearby elk herd in Great Smoky Mountains National Park to simulate pessimistic and optimistic recruitment and performed population viability analyses to evaluate sustainability over a 25-year period. Annual survival averaged 0.799 (Total SE = 0.023). The primary identifiable sources of mortality were poaching, disease from meningeal worm (Parelaphostrongylus tennis), and accidents (environmental causes and unintentional harvest). Population growth given pessimistic recruitment rates averaged 0.895 over 25 years (0.955 in year 1 to 0.880 in year 25); population growth was not sustainable in 100% of the runs. With the most optimistic estimates of recruitment, mean λ increased to 0.967 (1.038 in year 1 to 0.956 in year 25) with 99.6% of the runs failing to be sustainable. We suggest that further translocation efforts to increase herd size will be ineffective unless survival rates are increased in the Cumberland Mountains.
The abundance and distribution of corvids (Common Raven, Corvus corax; Hooded Crow, C. corone; Jackdaw, C. monedula; Black-billed Magpie, Pica pica; and European Jay, Garrulus glandarius) were studied across a gradient from a landscape dominated by agricultural land to a landscape dominated by forest in south-central Sweden. The total density and the predation rate on dummy nests increased as the proportion of agricultural land increased. This supports the suggestion that the density of corvids increases as forest becomes fragmented and intermixed with agricultural land, causing an increase in nest predation in small forest fragments. However, the different species responded differently to the proportion of forest in the landscape. The two forest-living corvids, the Jay and Raven, were absent from small forest fragments in a matrix of agricultural land and mainly preyed upon dummy nests inside the large forest fragments. Thus, both of these species were habitat specialists restricted to forests. Three corvids basically inhabit agricultural land, the Hooded Crow, Jackdaw, and Magpie. The Jackdaw and the Magpie showed a strong preference for agricultural land and they mainly preyed upon dummy nests in agricultural land. On the other hand, the density of Hooded Crows was higher in landscapes with a mixture of agricultural land and forest than in landscapes dominated by either agricultural land or forest, indicating a use of both agricultural land and forest. Further, Hooded Crows regularly preyed upon nests in both forest habitat and agricultural land; it is a habitat generalist. Therefore, the Hooded Crow was the most important species in the corvid family, causing increased predation pressure close to forest-farmland edges and in small forest fragments surrounded by agricultural land.
Abundant vertebrate remains from two mid-Wisconsin cave deposits in New Mexico allow reconstruction of paleoenvironments. Dry Cave lies in southeastern New Mexico, U-Bar Cave in the extreme southwest (Figure 1). Both sites are in the ecotone between woodland and Chihuahuan Desert vegetations. During the mid Wisconsin, both had vertebrate species indicative of woodland, but otherwise differed greatly. Dry Cave had winter temperatures milder than those at the site today, but otherwise the climate was similar to that now found some 450 km to the north. Except for taxa allowed into the area by mild winters, extralimital forms occur in nearby highland woodlands or in northeastern New Mexico. U-Bar Cave probably lacked winter freezes, had cool summers, and had precipitation more evenly distributed than now. Taxa now as distant as the Great Basin occurred together with species from the nearer highlands. Relatively warm summers and retention of seasonal patterns of precipitation at Dry Cave in contrast to cool summers and decreased seasonality of precipitation at U-Bar Cave produced more extreme biotic differences between the sites than is the case now. Whether this was due to different contemporaneous climatic regimes or to chronological differences between the faunas is uncertain.
Although ravens were once widespread throughout Appalachia they are now considered threatened or endangered in many states of the region. We document a nesting pair of common ravens in an area of southeastern Kentucky nearly 50 km northwest of traditional nesting sites. Further, we suggest several factors that may have influenced the patterns of raven abundance in the state and offer management recommendations to assist their recovery.
In the western Arctic and in the northwest coast and Alaska, the significance of the raven as a creator and trickster is generally acknowledged. In the eastern Arctic there are no such elaborate mythical cycles concerning the bird. But the raven still plays an important role in myths and rituals. In this paper, some features of the Alaskan complex and the position of the raven in the eastern Arctic are discussed. The basic features of the Alaskan raven complex are used as heuristic principles guiding research into the situation in the eastern Arctic region. It is argued that in many respects the raven is responsible for society but without being part of it. As a predator and a scavenger it is often associated with eating dirt, excrement and human flesh, and yet it created light, enabling people to see and invented tattooing, enabling women to marry.
The raven and crow skeletons from Danebury are re-examined, taking into account their taphonomy, their context and the associated finds. Raven and crow burials from other Iron Age and Roman sites are surveyed, again with a discussion of their context and associated finds where these could be ascertained. Taken together, the evidence makes it clear that most if not all were deliberate burials, often at the base of pits. We demonstrate how interpretations of such burials have changed, with zooarchaeologists initially proposing functional explanations and archaeologists readier to accept that the burials were deliberate. We go on to argue that the unique character of ravens and crows, including their tolerance of humans, their scavenging habits, and their voice, led to their playing an important role in Iron Age and Roman rites and beliefs.
Declines in hunter recruitment coupled with dramatic growth in numbers of white-tailed deer (Odocoileus virginianus) have challenged our ability to manage deer populations through regulated hunting. We review the efficacy of current regulated hunting methods and explain how they are unable to reduce deer numbers sufficiently in some environments. Regulated commercial harvest would provide an additional tool to help state wildlife agencies manage overabundant populations of white-tailed deer. We outline potential means to govern regulated commercial deer harvest and explain how it is compatible with the North American Model of Wildlife Conservation. We identified several benefits, including reduced overabundant populations of deer; source of healthy, natural, green, locally produced protein; promotion of economic growth, entrepreneurship, and market expansion; and public engagement and appreciation. We also address expected concerns associated with this concept, such as privatization of wildlife; overexploitation; food safety; competition with existing commodities; law enforcement; and challenges of changing laws, regulations, and attitudes. We suggest developing a professional forum to address the issue of regulated commercial harvest of white-tailed deer and other overabundant species of wildlife. © 2011 The Wildlife Society.
1. Recovering populations of predators and scavengers have often given rise to concerns about the impact they may have on prey species. Particularly, this is the case when the prey species are of economic or conservation importance.
2. Recovery of common raven Corvus corax populations in the UK and Europe has given rise to a conflict with some stakeholders over their concerns for both the protection of livestock and the possible detrimental impact on some upland bird species, particularly ground nesting waders. This has led to demands by some land managers for licences to lethally control ravens to protect upland breeding birds.
3. We used data from broad scale surveys of distribution and abundance of upland breeding birds in the UK carried out in 1980–1993 and 2000–2002 to test whether variation in raven abundance or change in raven abundance was negatively associated with changes in abundance of five species of waders.
4. We found no significant negative spatial or temporal relationships between ravens and any of the five species of waders. However, weak (0·05 < P < 0·1) negative relationships between raven abundance and trends of curlew Numenius arquata and lapwing Vanellus vanellus may warrant further investigation.
5. Synthesis and applications. Our study found no significant negative associations between raven abundance and population changes in upland waders, and so does not provide support to justify granting of licences for the lethal control of ravens in the interest of population-level conservation of these upland wader species. However, the near significant negative associations with lapwing and curlew merit further investigation. This study emphasizes the importance of making a thorough evaluation of the evidence base before making decisions regarding predator control.
Prediction of species’ distributions is central to diverse applications in ecology, evolution and conservation science. There is increasing electronic access to vast sets of occurrence records in museums and herbaria, yet little effective guidance on how best to use this information in the context of numerous approaches for modelling distributions. To meet this need, we compared 16 modelling methods over 226 species from 6 regions of the world, creating the most comprehensive set of model comparisons to date. We used presence-only data to fit models, and independent presence-absence data to evaluate the predictions. Along with well-established modelling methods such as generalised additive models and GARP and BIOCLIM, we explored methods that either have been developed recently or have rarely been applied to modelling species’ distributions. These include machine-learning methods and community models, both of which have features that may make them particularly well suited to noisy or sparse information, as is typical of species’ occurrence data. Presence-only data were effective for modelling species’ distributions for many species and regions. The novel methods consistently outperformed more established methods. The results of our analysis are promising for the use of data from museums and herbaria, especially as methods suited to the noise inherent in such data improve.
Four previously unreported records of Castoroides provide supportive evidence that the giant beaver probably occurred throughout the southeastern United States, especially along the middle stretch of the Tennessee River. A distal section of an upper right incisor and an incisor fragment of the extinct Pleistocene giant beaver, Castoroides, were recovered from Bell Cave, Colbert County, Alabama. Cave ACb-3, also in Colbert County and containing an extensive deposit of late Pleistocene megafauna, yielded a single incisor enamel fragment. A fragment of a left ilium of this beaver was found in a dry stream bed in Ruby Falls Cave, Lookout Mountain, Hamilton County, Tennessee. These four specimens are referred to Castoroides sp. A relatively complete skull of Castoroides has been recovered from the Cooper River, near Strawberry Hill, Charleston County, South Carolina. The cranial characters of this specimen make it referable to Castoroides leiseyorum Morgan and White, 1995, which was described from the Irvingtonian Leisey Shell Pit, Hillsborough County, Florida. The taxonomy of Castoroides from the southeastern United States is uncertain, and at least two different interpretations are possible.
Although there has been a surge of interest in density estimation in recent years, much of the published research has been concerned with purely technical matters with insufficient emphasis given to the technique’s practical value. Furthermore, the subject has been rather inaccessible to the general statistician. The account presented in this book places emphasis on topics of methodological importance, in the hope that this will facilitate broader practical application of density estimation and also encourage research into relevant theoretical work. The book also provides an introduction to the subject for those with general interests in statistics. The important role of density estimation as a graphical technique is reflected by the inclusion of more than 50 graphs and figures throughout the text. Several contexts in which density estimation can be used are discussed, including the exploration and presentation of data, nonparametric discriminant analysis, cluster analysis, simulation and the bootstrap, bump hunting, projection pursuit, and the estimation of hazard rates and other quantities that depend on the density. This book includes general survey of methods available for density estimation. The Kernel method, both for univariate and multivariate data, is discussed in detail, with particular emphasis on ways of deciding how much to smooth and on computation aspects. Attention is also given to adaptive methods, which smooth to a greater degree in the tails of the distribution, and to methods based on the idea of penalized likelihood.
Crows, rooks and ravens (Corvus spp.) display marked morphological and voice similarities that have been hypothesised to stem from competitive interactions, as a case of non-aposematic mimicry. Here, I test predictions of the mimicry hypothesis at the macrovolutionary scale, examining whether species morphological and acoustic traits covary with those of coexisting congeners, and whether phenotypic similarity has facilitated the coexistence of related species after secondary contact. Body size and the temporal patterns of the commonest call display high levels of similarity among sympatric species, even after controlling for the effect of shared climate and habitat, and phylogenetic constraints in the production of variation. When sister species differed in these acoustic and morphological traits, their transition to secondary sympatry was delayed relative to those with more similar traits. No similarity was found in the sexual call of crows, suggesting that convergence occurs only when function does not favour maintenance of species-specific traits. Crow similarities in morphological and acoustic features may therefore be associated with coevolving interactions with congeners, in line with a broad array of studies documenting convergence among species that interact aggressively or forage communally. This article is protected by copyright. All rights reserved.
Based on decades of increasing deer effects on local biodiversity, agricultural damage, and deer–vehicle collisions, we implemented a suburban white-tailed deer (Odocoileus virginianus) research and management program in 2007 on Cornell University lands in Tompkins County, New York, USA. We attempted to reduce deer numbers by surgically sterilizing female deer in the 445-ha suburban core campus via tubal ligation and ovariectomy. From 2007 to 2013, we sterilized 93 deer and radiocollared 67 adult females to monitor fawning. Tubal ligation and ovariectomy surgeries appeared to prevent birth in 96% and 100% of treated female deer, respectively. We implemented a camera survey, used a mark–resight model in Program NOREMARK to estimate annual deer abundance, and observed no reduction in female abundance by winter 2013. Conversely, we noted a 38% and 79% decrease of total adult females and fawns visible in sampled photographs, respectively, and an 873% increase in adult male visitation to camera traps on core campus. Surgical sterilization appeared to be ineffective for reducing the abundance of a geographically open population of white-tailed deer in the absence of lethal management. We do not recommend surgical sterilization as a stand-alone method for communities wishing to pursue mitigation of deer impacts with nonlethal approaches.
With the subtitle, 'The full fascinating story of Britain's landscape', the emphasis of this volume is on the earlier post-glacial history of both natural and man-made features in rural Britain. Whilst chapters recount the development of fields systems, heathland, moorland, grassland and wetlands, most attention is paid to woods and wood-pastures, and their significance in both the natural environments and the economic and social life of the rural populations. Chapters are devoted to the history of hedgerows and walls, the extinction and introduction of animal species, and the changing fortunes of the elm. In addition to a chapter on conservation, conservation sections are included in most other chapters, highlighting the need for changes in current policies towards the agricultural and silvicultural uses of the countryside. -J.Sheail
Steady technological advancements including subminiaturization of telemetry components, smaller and more accurate global positioning systems (GPSs), and increasingly available geographic information systems (GISs) continue to influence the way researchers collect and analyze wildlife radio-tracking data. These developments have increased the diversity of animals that can be studied and have boosted the number and accuracy of location estimates, within a framework of contemporary conservation issues. This chapter conducts a literature review using the Wildlife Worldwide (WW) database to assess the specific topics and number of studies using radiotelemetry in wildlife research. Databases within the WW search engine include Wildlife Review Abstracts (formerly Wildlife Review), Swiss Wildlife Information Service, Wildlife Database, BIODOC, and the Waterfowl and Wetlands database. The most critical assumption in any radiotelemetry study is that the transmitter has no appreciable effect on the study animal. One can assume that a marked animal behaves, functions, and survives in a manner similar to that of an unmarked animal. Despite this critical assumption, the impact of radio marking of animals has often been subjectively evaluated. Generally, researchers assume that large animals are not affected by radio marking, whereas smaller animals, particularly birds, are impacted more.
In the boreal forest region, partial-harvest silviculture has been garnering increasing interest as a means of maintaining wildlife species and habitat structure associated with late-successional forests. If late-successional species can find suitable habitat in partially harvested stands with a given level of structural retention, then partial harvesting might represent a viable silvicultural tool for maintaining wildlife dependent on mature or old-forest habitat within managed stands over time. Here we summarize literature on the responses of late-successional amphibians, birds, and mammals in Ontario's boreal region to various intensities of partial harvesting. We assess species responses from comparisons of habitat use in harvested and unharvested stands; we do not explicitly consider impacts of partial harvesting applied over large areas across the landscape. At the stand scale, light-intensity harvesting (70% retention) negatively affects several passerine birds, as well as spruce grouse winter habitat, but most late-successional species (including all mammals and amphibians considered) appear to be tolerant of this level of habitat alteration. Moderate-intensity harvesting (50% retention) was found to reduce the abundance of about 40% of the species considered, particularly cavity- and snag-dependent species (martens, northern flying squirrels, owls) and passerine birds that forage or nest in the canopy and understory. Highintensity (30% retention) partial harvesting was found to provide unsuitable habitat for about one quarter of all late-successional species, including most forest raptors, pileated and black-backed woodpeckers, brown creepers, northern flying squirrels, and woodland caribou. Also, studies indicate that additional passerine bird species would decrease in abundance, as would small, moisture-dependent, terrestrial species such as short-tailed shrews, red-backed voles, and eastern red-backed salamanders. There is a need to strengthen our understanding of responses to partial harvesting for nonpasserine birds and large mammals, and to verify species responses through experimental studies within Ontario's boreal region.
(1) The breeding raven population of southern Scotland and Northumberland was formerly (pre-1960) characterized by year-to-year stability in both numbers and distribution. The 123 known pairs occupied traditional nest-sites on cliffs or trees. Breeding density was correlated with altitude (greatest on high ground) and land productivity (greater on base-poor granite than on sedimentary rocks). This was probably linked with a greater availability of sheep carrion on high ground and base-poor ground. (2) The breeding population has been declining since the 1960s, and in 1974-5 only 55% of former regular nesting areas were still occupied, with breeding pairs reduced to 44%. This was mainly associated with the afforestation of former sheepwalk. The argument is based on a geographical parallel (greatest decline in areas with most afforestation), and on a temporal parallel (desertion of particular nesting areas coincident with planting in the area surrounding the nest sites). (3) The level of afforestation at which ravens deserted varied between nesting areas. Probably it depended on the overall quality of the original habitat, and the alternative food sources available: good habitat could take more afforestation before it became untenable than could poor habitat. (4) Not all desertion of nesting areas could be attributed to afforestation: four raven pairs were dispossessed from cliff nest-sites by golden eagles which recolonized southern Scotland over the period considered, and at least five other pairs by rock climbers. Sheep management also improved over the years, and may have contributed to the desertion of some marginal nesting areas, by leading to a reduction in the amount of carrion available. Organo-chlorine compounds and persecution are unlikely to have been involved in the decline. (5) In the Lake District, a comparable hill area with practically no afforestation, there was no decline in the numbers of breeding ravens over the same period. (6) Among the pairs studied in 1974-6, those occupying the most heavily afforested ground showed more non-breeding, and produced later, smaller broods than did those on less afforested ground. Those nesting areas still occupied and where more than 25% of former sheepwalk within 5 km had been afforested, produced later and smaller broods than they did before afforestation. (7) To judge from pellets, sheep carrion formed a major part of the diet, but a great variety of other foods available from grassland was also eaten. The percentage frequency of sheep remains in pellets declined significantly with increasing afforestation in the area around the nest-sites. (8) The prediction is made of a further decline in raven breeding numbers if blanket afforestation continues to expand over former upland sheepwalk.
Four previously unreported records of Castoroides provide sup-portive evidence that the giant beaver probably occurred through-out the southeastern United States, especially along the middle stretch of the Tennessee River. A distal section of an upper right incisor and an incisor fragment of the extinct Pleistocene giant beaver, Castoroides, were recovered from Bell Cave, Colbert County, Alabama. Cave ACb-3, also in Colbert County and con-taining an extensive deposit of late Pleistocene megafauna, yielded a single incisor enamel fragment. A fragment of a left ilium of this beaver was found in a dry stream bed in Ruby Falls Cave, Lookout Mountain, Hamilton County, Tennessee. These four specimens are referred to Castoroides sp. A relatively complete skull of Castoroides has been recovered from the Cooper River, near Strawberry Hill, Charleston County, South Carolina. The cranial characters of this specimen make it referable to Castoroides leiseyorum Morgan and White, 1995, which was described from the Irvingtonian Leisey Shell Pit, Hills-borough County, Florida. The taxonomy of Castoroides from the southeastern United States is uncertain, and at least two different interpretations are possible.
The Common Raven (Corvus corax) inhabits a region 80-160 km wide extending along the Appalachian Mountains from northern Georgia to north- ern Pennsylvania. The raven is generally described in the regional literature as a wary species that avoids man and his activities by nesting on cliffs in remote mountainous areas at high elevations (Harlow 1922, Murray 1949, Stupka 1963:101-103, and others). A species with these characteristics could be seriously disadvantaged by intensive use of the southern Appalachians for recreation and raw materials. This study was conducted to better define the ecological latitude in which the raven exists in a portion of the southern Appalachians. Study area.-The study was conducted northwest of Radford, Salem, and Lexington, and southeast of the West Virginia state line. Quartzite cliffs occur on ridges and in water gaps. Shale cliffs are usually adjacent to streams. Limestones and dolomites form bluffs on the Maury and New rivers. Valley elevations are 275-305 m on the James River and 470-538 m on the New River, while ridges rise to 1318 m above sea level. Over 85% of the study area is forest and the remainder is pasture and urban area. Mountain slopes are forested with mixtures of oaks (Q~ercus spp.) and other hardwoods. Xeric ridges are covered in Virginia, Table Mountain and pitch pine (Pinus virginiana, P. p~ngens, and P. rigida). Mesic ravines are forested with hemlock (Tsuga canadensis) ,
The current breeding ranges of Buzzards Buteo buteo and Ravens Corvus corax in Britain are restricted to the west, and both are relics of former widespread but not necessarily even distributions. Moore (1957) attributed the Buzzard's contraction in range to persecution by gamekeepers, his evidence being the complementary nature of the Buzzard's distribution with those of gamekeepers in the lowlands and grouse moors in the uplands; others have attributed the Raven's decline to the same cause. Is Moore correct and, if so, are these species' ranges still limited by persecution? Here we adopt an approach similar to Moore's, whereby we compare the current geographical patterns of abundance of Buzzards and Ravens in the British uplands with that of an index of grouse moor density. Unlike Moore, however, we take into account climate, land cover, topography and sheep stocking density, as well as grouse moor distribution, using multiple logistic regression modelling. We show that in the uplands the distribution of grouse moors strongly limits that of Buzzards and Ravens but are unable to conclude that this is a result of persecution because there are several competing hypotheses (moor management, food and nest-site availability) between which we are unable to distinguish.
The names of native wildlife species are attached to thousands of landmarks throughout the United States. We used a U.S. Geological Survey online database to assess the abundance, distribution, density, and historical range fidelity of 24 faunal place names within the continental United States and Alaska. Our search generated over 35,000 faunal place names distributed across 49 states, with overall highest densities in mountainous regions. The distribution of place names corroborates the familiar pattern of range constriction characteristic of many species during the past century. Place names of range-limited species demonstrated strong fidelity to historical ranges. The spatial patterns of faunal place names are important indicators of a species' historical distribution. Furthermore, these place names reflect culturally important connections between humans and native fauna. Prudent analysis of place names may provide important biogeographical information for maintaining or restoring species and habitat components, although its utility will likely be limited to large, charismatic species.
Abstract Aim To investigate the information content of place-names regarding the habits, habitat and biogeography of ravens in Britain over the past millennium.
Location England, Scotland and Wales.
Methods Linguistic and ecological analysis of over 400 British place-names that have a putative ‘raven’ derivation.
Results Most of the ‘raven’ place-names are Old English in origin. Some of these (a minority), however, derive from personal names. The derivations of most names reflect landscape rather than man-made features; the majority relating to high, craggy ground or coastal features, a minority to wooded situations or human habitations. In lowland Scotland and the Scottish borders the colloquial name corbie dominates ‘raven’ place-names, perhaps reflecting French influence. In the Highlands and the Western Isles the Gaelic fitheach and its derivatives are predominant. Relatively fewer place-names that have ‘raven’ roots have been educed in other parts of the Celtic West, i.e. Wales and Cornwall (only one traced in the latter).
Main conclusions Comparison of the geographical distribution of ‘raven’-derived place-names with the present-day distribution of the species in Britain reveals the extent of the contraction in the raven's range to the West over historical time, most notably during theprevious two centuries, associated with changed land-management practices in particular.
1. Trends of animal populations are of great interest in ecology but cannot be directly observed owing to imperfect detection. Binomial mixture models use replicated counts to estimate abundance, corrected for detection, in demographically closed populations. Here, we extend these models to open populations and illustrate them using sand lizard Lacerta agilis counts from the national Dutch reptile monitoring scheme.
2. Our model requires replicated counts from multiple sites in each of several periods, within which population closure is assumed. Counts are described by a hierarchical generalized linear model, where the state model deals with spatio-temporal patterns in true abundance and the observation model with imperfect counts, given that true state. We used WinBUGS to fit the model to lizard counts from 208 transects with 1–10 (mean 3) replicate surveys during each spring 1994–2005.
3. Our state model for abundance contained two independent log-linear Poisson regressions on year for coastal and inland sites, and random site effects to account for unexplained heterogeneity. The observation model for detection of an individual lizard contained effects of region, survey date, temperature, observer experience and random survey effects.
4. Lizard populations increased in both regions but more steeply on the coast. Detectability increased over the first few years of the study, was greater on the coast and for the most experienced observers, and highest around 1 June. Interestingly, the population increase inland was not detectable when the observed counts were analysed without account of detectability. The proportional increase between 1994 and 2005 in total lizard abundance across all sites was estimated at 86% (95% CRI 35–151).
5.Synthesis and applications. Open-population binomial mixture models are attractive for studying true population dynamics while explicitly accounting for the observation process, i.e. imperfect detection. We emphasize the important conceptual benefit provided by temporal replicate observations in terms of the interpretability of animal counts.
In this paper kernel methods for the nonparametric estimation of the utilization distribution from a random sample of locational observations made on an animal in its home range are described. They are of flexible form, thus can be used where simple parametric models are found to be inappropriate or difficult to specify. Two examples are given to illustrate the fixed and adaptive kernel approaches in data analysis and to compare the methods. Various choices for the smoothing parameter used in kernel methods are discussed. Since kernel methods give alternative approaches to the Anderson (1982) Fourier transform methods, some comparisons are made.
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Observation or sampling error in population monitoring can cause serious degradation of the inferences, such as estimates of trend or risk, that ecologists and managers frequently seek to make with time-series observations of population abundances. We show that replicating the sampling process can considerably improve the information obtained from population monitoring. At each sampling time the sampling method would be repeated, either simultaneously or within a short time. In this study we examine the potential value of replicated sampling to population monitoring using a density-dependent population model. We modify an existing population time-series model, the Gompertz state-space model, to incorporate replicated sampling, and we develop maximum-likelihood and restricted maximum-likelihood estimates of model parameters. Depending on sampling protocols, replication may or may not entail substantial extra cost. Some sampling programs already have replicated samples, but the samples are aggregated or pooled into one estimate of population abundance; such practice of aggregating samples, according to our model, loses considerable information about model parameters. The gains from replicated sampling are realized in substantially improved statistical inferences about model parameters, especially inferences for sorting out the contributions of process noise and observation error to observed population variability.
Species’ assessments must frequently be derived from opportunistic observations made by volunteers (i.e., citizen scientists). Interpretation of the resulting data to estimate population trends is plagued with problems, including teasing apart genuine population trends from variations in observation effort. We devised a way to correct for annual variation in effort when estimating trends in occupancy (species distribution) from faunal or floral databases of opportunistic observations. First, for all surveyed sites, detection histories (i.e., strings of detection–nondetection records) are generated. Within-season replicate surveys provide information on the detectability of an occupied site. Detectability directly represents observation effort; hence, estimating detectablity means correcting for observation effort. Second, site-occupancy models are applied directly to the detection-history data set (i.e., without aggregation by site and year) to estimate detectability and species distribution (occupancy, i.e., the true proportion of sites where a species occurs). Site-occupancy models also provide unbiased estimators of components of distributional change (i.e., colonization and extinction rates). We illustrate our method with data from a large citizen-science project in Switzerland in which field ornithologists record opportunistic observations. We analyzed data collected on four species: the widespread Kingfisher (Alcedo atthis) and Sparrowhawk (Accipiter nisus) and the scarce Rock Thrush (Monticola saxatilis) and Wallcreeper (Tichodroma muraria). Our method requires that all observed species are recorded. Detectability was <1 and varied over the years. Simulations suggested some robustness, but we advocate recording complete species lists (checklists), rather than recording individual records of single species. The representation of observation effort with its effect on detectability provides a solution to the problem of differences in effort encountered when extracting trend information from haphazard observations. We expect our method is widely applicable for global biodiversity monitoring and modeling of species distributions.
Resumen: Las evaluaciones de especies frecuentemente deben ser derivadas de observaciones oportunistas de voluntarios (i.e., científicos ciudadanos). La interpretación de los datos resultantes para estimar las tendencias poblacionales está plagada de problemas, incluyendo la distinción entre las tendencias poblacionales genuinas y las variaciones en el esfuerzo de observación. Diseñamos un método para corregir la variación anual en el esfuerzo en la estimación de las tendencias en la ocupación (distribución de especies) a partir de bases de datos de observaciones oportunistas de fauna o flora. Primero, se generan historias de detección para todos los sitios muestreo (i.e., cadenas de registros de detección-no detección). Muestreos intraestacionales replicados proporcionan información sobre la detectabilidad de un sitio ocupado. La detectabilidad representa el esfuerzo de observación directamente; por lo tanto, la estimación de la detectabilidad significa la corrección del esfuerzo de observación. Segundo, los modelos de ocupación de sitios son aplicados directamente al conjunto de datos de la historia de detección (i.e., sin agregación por sitio y año) para estimar la detectabilidad y distribución de especies (ocupación, i.e., la proporción real de sitios donde ocurre una especie). Los modelos de ocupación de sitios también proporcionan una estimación no sesgada de los componentes de un cambio en la distribución (i.e., tasas de colonización y extinción). Ilustramos nuestro método con datos de un proyecto de ciencia ciudadana en Suiza en el cual ornitólogos de campo registran observaciones oportunistas. Analizamos datos recolectados para cuatro especies: Alcedo atthis y Accipiter nisus ampliamente distribuidas y Monticola saxatilis y Tichodroma muraria que son escasas. Nuestro método requiere que todas las especies observadas sean registradas. La detectabilidad fue <1 y varió a lo largo de los años. Las simulaciones sugirieron alguna robustez, pero propugnamos que se elaboren listas de especies completas (listas de control), en lugar de registrar observaciones individuales de una sola especie. La representación del esfuerzo de observación con su efecto sobre la detectabilidad proporciona una solución al problema de diferencias en el esfuerzo cuando se extrae información de tendencias a partir de observaciones casuales. Consideramos que nuestro método es ampliamente aplicable al monitoreo de la biodiversidad global y al modelado de la distribución de especies.