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Glaciers worldwide are currently retreating at unprecedented rates, revealing large tracts of newly exposed rock and till. We present the results of a preliminary, qualitative investigation of the lichen diversity of transient habitats near three glaciers in southeastern Alaska: Muir Glacier within Glacier Bay National Park, and Baird and Patterson Glaciers in the Tongass National Forest. This work is noteworthy as it (i) documents previously undescribed lichen species and communities within rapidly changing glacier habitats, (ii) illustrates the importance of cryptogams (lichens, bryophytes, algae, and cyanobacteria) in the primary colonization of recently deglaciated terrain, (iii) sets apart the lichen biota of recently deglaciated terrain in southeastern Alaska from that of other glacial regions worldwide (e.g., the European Alps, Svalbard, and southern South America) and even other parts of Alaska (e.g., Brooks Range), and (iv) emphasizes the importance of more lichen studies that focus on this rapidly changing habitat. The lichen biotas found at different successional stages near these glaciers are described and compared. The role of lichens and other cryptogams in post-glacial vegetation initiation, the threats to the lichen biota, and suggestions for the possible origins of the lichen propagules that colonize these newly exposed surfaces are also discussed. Key words: climate change, maritime glaciers, post-glacial succession, prolonged snow-lie, rare lichen species. Les glaciers à travers le monde reculent actuellement à des taux sans précédent, révélant de grandes étendues de roches et de till nouvellement exposées. Les auteurs présentent les résultats d'une étude qualitative préliminaire sur la diversité des lichens des habitats transitoires près de trois glaciers du sud-est de l'Alaska : le glacier Muir dans le parc national de Glacier Bay et les glaciers Baird et Patterson dans la forêt nationale de Tongass. Ce travail est notable, car il (i) documente des espèces et des communautés de lichens non décrites jusqu'à présent dans des habitats glaciaires en évolution rapide, (ii) illustre l'importance des cryptogames (lichens, bryophytes, algues et cyanobactéries) dans la colonisation primaire des terrains récemment déglacés, (iii) distingue le biote lichénique des terrains récemment déglacés du sud-est de l'Alaska de celui d'autres régions glaciaires du monde (p. ex. les Alpes européennes, le Svalbard et le sud de l'Amérique du Sud) et même d'autres parties de l'Alaska (p. ex. la chaîne de Brooks), et (iv) souligne l'importance d'autres études sur les lichens qui se concentrent sur cet habitat en évolution rapide. Les biotopes de lichens trouvés à différents stades de succession près de ces glaciers sont décrits et comparés. Le rôle des lichens et d'autres cryptogames dans l'initiation de la végétation postglaciaire, les menaces qui pèsent sur le biote lichénique et les suggestions sur les origines possibles des propagules de lichens qui colonisent ces surfaces nouvellement exposées sont également discutés. [Traduit par la Rédaction] Mots-clés : changement climatique, glaciers maritimes, succession postglaciaire, couche de neige prolongée, espèces de lichens rares., Introduction Southeastern Alaska (also known as the Alaska Panhandle and hereinafter referred to as SE Alaska) is a region of particularly active geologic processes that have resulted in an exceptionally [...]

Availability of suitable habitat affects the distribution and abundance of Arctic fauna, influencing how species respond to climate change and disturbance from resource extraction in the region. We surveyed Arctic ground squirrels (Urocitellus parryii (Richardson, 1825)) using distance sampling transects and concurrently counted microtine rodent burrows. Abundance of Arctic ground squirrels and microtine burrows was positively correlated with terrain ruggedness. Microtine burrows were more abundant inland and in areas with freshwater, whereas Arctic ground squirrels were more often found at low elevation without freshwater. Arctic ground squirrel abundance was positively related to the normalized difference water index, a proxy for vegetation water content, whereas microtine burrows were weakly correlated with the normalized difference vegetation index. Our study highlights the habitat associations of ecologically significant small mammals in an underrepresented Arctic study area. Key words: Arctic ground squirrel, distance sampling, Urocitellus parryii, microtine rodents, habitat associations, density surface modelling. La disponibilité d'habitats convenables a une incidence sur la répartition et l'abondance des animaux arctiques, influençant la réaction des espèces aux changements climatiques et aux perturbations causées par l'extraction de ressources dans la région. Nous avons examiné les spermophiles arctiques (Urocitellus parryii (Richardson, 1825)) en utilisant des transects d'échantillonnage par la distance et en comptant simultanément les terriers de microtinés. Les abondances des spermophiles arctiques et des terriers de microtinés présentent une corrélation positive avec la rugosité du terrain. Les terriers de microtinés sont plus abondants à l'intérieur des terres et dans les secteurs avec présence d'eau douce, alors que les spermophiles arctiques sont observés le plus souvent dans des secteurs de faible altitude sans présence d'eau douce. L'abondance des spermophiles arctiques est positivement reliée à l'indice normalisé d'eau, une variable reflétant la teneur en eau de la végétation, alors que le nombre de terriers de microtinés est faiblement corrélé à l'indice normalisé de végétation. Notre étude fait ressortir des associations d'habitats de petits mammifères d'importance écologique dans une région d'étude sous-représentée de l'Arctique. [Traduit par la Rédaction] Mots-clés : spermophile arctique, échantillonnage par la distance, Urocitellus parryii, microtinés, associations d'habitats, modélisation spatiale de la densité., Introduction Abundance and distribution of Arctic wildlife are key areas of study as habitats become altered due to climate change (Meredith et al. 2019) and increased resource extraction (Haley et [...]

Lincoln's sparrow (Melospiza lincolnii) is a common wintering bird species across the southern USA, Mexico, and northern Central America. Unlike many migratory sparrows, which are grassland or savannah species, Lincoln's [...]

Monitoring marine mammal populations and their habitats is crucial for assessing population status and defining realistic management and conservation goals. Environmental and anthropogenic changes in the Arctic have prompted the pursuit for improved understanding of female beluga whale (Delphinapterus leucas) spatial and temporal reproductive patterns. There are relatively few estimates for female reproductive parameters of beluga whale populations across the Arctic, and those few that are available are outdated. Here we summarize female reproductive data from samples collected through Inuit subsistence hunts of three eastern Canadian Arctic beluga populations: High Arctic/Baffin Bay (HA), Western Hudson Bay (HB), and Cumberland Sound (CS) from 1989 to 2014. We grouped the CS and HA populations into a Baffin Bay region (BB) population based on similar body growth patterns and genetic similarity. Asymptotic body length of BB beluga whales (370.9 cm) was greater than HB whales (354.4 cm) as established from Gompertz growth curves fitted for whales ranging in age from 1-89 y. We did not detect a significant difference in average number of pseudocervices (8.6) between regions. Differences in average age of sexual maturity (ASM) and length at sexual maturity (LSM) were identified, with evidence of BB females maturing earlier than females from HB (probability method BB = 9.9 y versus HB = 11.0 and logistic method ASM50% HB = 9.99 and BB unresolved). BB females were also longer than HB females at maturing age (logistic LSM50%: BB = 314.5 cm vs HB = 290.3). Total corpora counts were strongly correlated with age, although the number of corpora ([greater than or equal to] 10 mm) suggests reproductive senescence between 40 and 50 y. Improved understanding of female reproductive patterns and knowledge of changes in the spatial and temporal timing of reproductive processes are fundamental for effective conservation and sustainable management of beluga whale populations. Key words: age of sexual maturity; body growth; vaginal folds; corpora lutea; pseudocervices; reproductive activity La surveillance des populations de mammiferes marins et de leurs habitats joue un role crucial dans revaluation de l'etat d'une population ainsi que dans la formulation d'objectifs realistes en matiere de gestion et de conservation. Dans l'Arctique, les changements environnementaux et anthropiques incitent a mieux comprendre les tendances spatiales et temporelles de reproduction du beluga femelle (Delphinapterus leucas). Il existe relativement peu d'estimations des parametres de reproduction des femelles au sein des populations de belugas de l'Arctique, et celles qui existent ne sont plus a jour. Nous resumons ici les donnees de reproduction des femelles en fonction d'echantillons recueillis a partir des chasses de subsistance d'Inuits parmi trois populations de belugas de l'est de l'Arctique canadien : Extreme-Arctique et baie de Baffin (HA), ouest de la baie d'Hudson (HB) et detroit de Cumberland (CS), de 1989 a 2014. Nous avons regroupe les populations de CS et de HA dans une population de la region de la baie de Baffin (BB) en fonction de tendances de croissance corporelle semblables et de similarite genetique. La longueur corporelle asymptotique des belugas de BB (370,9 cm) etait plus grande que celle des baleines de HB (354,4 cm), ainsi determinee a l'aide des courbes de croissance de Gompertz adaptees aux baleines, dont l'age varie de un an a 89 ans. Nous n'avons pas detecte de difference importante dans le nombre moyen de << pseudo-cols de l'uterus >> (8,6) entre les regions. Des differences dans l'age moyen de la maturite sexuelle (ASM) et dans la longueur a la maturite sexuelle (LSM) ont ete decelees, avec preuve que les femelles de BB arrivaient plus vite a maturite que les femelles de HB (methode de probabilite de BB = 9,9 ans par opposition a HB = 11,0 et une methode de logistique d'ASM50% HB = 9,99 et de BB non resolue). Par ailleurs, les femelles de BB etaient plus longues que les femelles de HB a l'age de la maturite (logistique LSM50% : BB = 314,5 cm par opposition a HB = 290,3). Le nombre total de corps jaunes etait fortement correle a l'age, bien que le nombre de corps jaunes ([greater than or equal to] 10 mm) suggere une senescence reproductive variant entre 40 et 50 ans. Une meilleure comprehension des tendances de reproduction des femelles et de meilleures connaissances des changements spatiaux et temporels des processus de reproduction revetent une importance fondamentale pour la conservation efficace et la gestion durable des populations de belugas. Mots cles : age de la maturite sexuelle; croissance corporelle; rides du vagin; corps jaune; pseudo-cols de l'uterus; activite reproductive Traduit pour la revue Arctic par Nicole Giguere., INTRODUCTION Marine mammals are typically apex predators in Arctic marine ecosystems, provide country food for Inuit communities, and function as indicators of ecosystem health and environmental change (Moore and Huntington, [...]

Habitat attributes of submerged aquatic vegetation and floating-leaved aquatic vegetation were analyzed from survey data collected in estuaries and coastal river systems of Mississippi and Mobile Bay, Alabama. The objectives [...]

Understanding how ecological communities are organized and how they change through time is critical to predicting the effects of climate change (1). Recent work documenting the co-occurrence structure of modern communities found that most significant species pairs co-occur less frequently than would be expected by chance (2,3). However, little is known about how co-occurrence structure changes through time. Here we evaluate changes in plant and animal community organization over geological time by quantifying the co-occurrence structure of 359,896 unique taxon pairs in 80 assemblages spanning the past 300 million years. Co-occurrences of most taxon pairs were statistically random, but a significant fraction were spatially aggregated or segregated. Aggregated pairs dominated from the Carboniferous period (307 million years ago) to the early Holocene epoch (11,700 years before present), when there was a pronounced shift to more segregated pairs, a trend that continues in modern assemblages. The shift began during the Holocene and coincided with increasing human population size (4,5) and the spread of agriculture in North America (6,7). Before the shift, an average of 64% of significant pairs were aggregated; after the shift, the average dropped to 37%. The organization of modern and late Holocene plant and animal assemblages differs fundamentally from that of assemblages over the past 300 million years that predate the large-scale impacts of humans. Our results suggest that the rules governing the assembly of communities have recently been changed by human activity., How are plant and animal communities organized, and does their structure change through time? This question has dominated many decades of research on community assembly rules and is critical to [...]

Despite the recent burgeoning in predator tracking studies, few report on seabird activity patterns, despite the potential to provide important insights into foraging ecology and distribution. In the first year-round study for any small petrel, we examined the activity patterns of the white-chinned petrel Procellaria aequinoctialis based on data from combination geolocator-immersion loggers deployed on adults at South Georgia. The petrels were highly nocturnal, flying for greater proportions of darkness than any large procellarid studied so far, except the light-mantled albatross Phoebetria palpebrata. Flight bout durations were short compared with other species, suggesting a dominant foraging mode of small-scale searching within large prey patches. When migrating, birds reduced the proportion of time on the water and increased flight bout duration. Activity patterns changed seasonally: birds flew least during the nonbreeding period, and most frequently during chick-rearing in order to meet higher energy demands associated with provisioning offspring. The degree of their response to moonlight was also stage dependent (greatest in nonbreeding, and weakest in incubating birds), a trait potentially shared by other nocturnal petrels which will have repercussions for feeding success and prey selection. For the white-chinned petrel, which is commonly caught in longline fisheries, these results can be used to identify periods when birds are most susceptible to bycatch, and therefore when use of mitigation and checking for compliance is critical., Author(s): Elizabeth K. Mackley [sup.1] [sup.2] , Richard A. Phillips [sup.1] , Janet R. D. Silk [sup.1] , Ewan D. Wakefield [sup.1] , Vsevolod Afanasyev [sup.1] , Robert W. Furness [...]

Ecosystem engineers are species that alter the physical environment in ways that create new habitat or change the suitability of existing habitats for themselves or other organisms. In marine systems, much of the focus has been on species such as corals, oysters, and macrophytes that add physical structure to the environment, but organisms ranging from microbes to jellyfish and finfish that reside in the water column of oceans, estuaries, and coastal seas alter the chemical and physical environment both within the water column and on the benthos. By causing hypoxia, changing light regimes, and influencing physical mixing, these organisms may have as strong an effect as species that fall more clearly within the classical category of ecosystem engineer. In addition, planktonic species, such as jellyfish, may indirectly alter the physical environment through predator-mediated landscape structure. By creating spatial patterns of habitats that vary in their rates of mortality due to predation, planktonic predators may control spatial patterns and abundances of species that are the direct creators or modifiers of physical habitat. doi: 10.1093/icb/icq051

The importance of positive interactions is increasingly acknowledged in contemporary ecology. Most research has focused on direct positive effects of one species on another. However, there is recent evidence that indirect positive effects in the form of facilitation cascades can also structure species abundances and biodiversity. Here we conceptualize a specific type of facilitation cascade--the habitat cascade. The habitat cascade is defined as indirect positive effects on focal organisms mediated by successive facilitation in the form of biogenic formation or modification of habitat. Based on a literature review, we demonstrate that habitat cascades are a general phenomenon that enhances species abundance and diversity in forests, salt marshes, seagrass meadows, and seaweed beds. Habitat cascades are characterized by a hierarchy of facilitative interactions in which a basal habitat former (typically a large primary producer, e.g., a tree) creates living space for an intermediate habitat former (e.g., an epiphyte) that in turn creates living space for the focal organisms (e.g., spiders, beetles, and mites). We then present new data on a habitat cascade common to soft-bottom estuaries in which a relatively small invertebrate provides basal habitat for larger intermediate seaweeds that, in turn, generate habitat for focal invertebrates and epiphytes. We propose that indirect positive effects on focal organisms will be strongest when the intermediate habitat former is larger and different in form and function from the basal habitat former. We also discuss how humans create, modify, and destroy habitat cascades via global habitat destruction, climatic change, over-harvesting, pollution, or transfer of invasive species. Finally, we outline future directions for research that will lead to a better understanding of habitat cascades. doi: 10.1093/icb/icq042

Biogenic forces alter sediment characteristics along several axes with important consequences for structure of benthic communities. The usual axes discussed are those of sediment stabilization versus resuspension and mobile versus temporally persistent organisms. A third axis of bioadvection is typically subsumed within the others. Here we argue that given the complex fluid dynamics resulting from the bidirectional forces that organisms exert on porewater, bioadvection needs to be examined separately. The probable major players in generation of bioadvection are described with impacts on transport both of materials and heat. Illustrations are given of the bidirectionality of bioadvection and the resultant changes in oxygenation either surficially or at depth, as well as of heat transport both laterally within the sediment and vertically. doi: 10.1093/icb/icq031

We estimated the sampling effort required to accurately estimate species richness and to detect changes in catch-per-unit-effort (CPUE) in four Great Plains, USA, streams. The number of sampled reaches (i.e., 1% of total catch) with [beta] = 0.80 ranged from 7 to 630 (mean = 99) and decreased with longer sampled reaches. A greater number of sampled reaches were needed to detect 90% of species richness and 25% changes in CPUE when Jaccard's similarity of samples of stream fish assemblages and habitat heterogeneity was lower within streams. Our results suggest that homogeneous stream segments require more sampled reaches to characterize fish assemblages and monitor trends in fish abundance. Nous avons estime l'effort d'echantillonnage requis pour evaluer correctement la richesse specifique et pour detecter les changements dans les prises par unite d'effort (CPUE) dans quatre cours d'eau de la region des Grandes Plaines, E.-U. Le nombre de sections echantillonnees (de 1% des captures totales) avec [beta] = 0,80 varie de 7 a 630 (moyenne = 99) et decroit si les sections echantillonnees sont plus longues. Il faut echantillonner un plus grand nombre de sections afin de detecter 90 % de la richesse specifique et des changements de 25 % de CPUE lorsque la similarite de Jaccard est plus faible dans les echantillons des peuplements de poissons et que l'heterogeneite des habitats est reduite dans les cours d'eau. Nos resultats indiquent que, dans les segments homogenes de cours d'eau, il faut echantillonner un plus grand nombre de sections afin de caracteriser les peuplements de poissons et de suivre les tendances d'abondance des poissons. [Traduit par la Redaction], Introduction Stream fish assemblages are often sampled at a few locations to describe species richness and catch-per-unit-effort (CPUE) of individual species across a larger spatial scale. These data are then [...]

The study results from raptor monitoring and contamination in Norway of the golden eagle, gyrfalcon, white-tailed sea eagle, osprey, peregrine, and merlin is summarized. The results from monitoring showed no long-term trends in productivity, and the populations of most raptors are stable or increasing and revealed the significance of long-term monitoring to predict future threats from habitat change and climate change that could have negative impacts on populations.

Understanding habitat quality for birds is crucial for ecologists and managers, but few papers have explored the advantages and disadvantages of different ways to measure it. In this review I clarify terminology and distinguish habitat quality from related terms, differentiate habitat quality at the levels of individual birds and populations, and describe different field methods for measuring habitat quality. As much as feasible, biologists concerned with habitat quality should emphasize demographic variables while recognizing that reproduction, survival, and abundance may not all be positively correlated. The distribution of birds can also reveal habitat quality (e.g., through patterns of habitat selection), but researchers should first investigate how closely their subjects follow ideal distributions because numerous ecological factors can lead birds to select poor and avoid rich habitats. Measures of body condition can provide convenient measures of habitat quality, but to be useful they must be a consequence, rather than a cause, of habitat selection. Habitat ecologists should use caution before relying on shortcuts from more labor-intensive demographic work. To increase the reliability of our habitat quality measurements, we should work to develop new methods to assess critical assumptions of nondemographic indicators, such as whether birds follow ideal distributions under natural conditions and whether spatial variation in body condition manifests in differential fitness. Key words: body condition, demography, distribution, habitat preference, habitat quality, habitat selection, habitat suitability. Entender la calidad del habitat de las aves es crucial para los ecologos y los encargados del manejo ambiental, pero pocos articulos han explorado las ventajas y desventajas de distintos metodos para medirla. En esta revision, aclaro la terminologia y diferencio la calidad del habitat de otros terminos relacionados, distingo la calidad del habitat a nivel de aves individuales y de poblaciones y describo diferentes metodos de campo para medir la calidad del habitat. En la medida de lo posible, los biologos interesados en la calidad del habitat deberian enfatizar variables demograficas, y tener en cuenta que la reproduccion, supervivencia y abundancia podrian no estar correlacionadas. La distribucion de las aves tambien puede indicar la calidad del habitat (e.g., a traves de patrones de seleccion de habitat), pero los investigadores deberian primero investigar hasta que punto sus sujetos de estudio presentan distribuciones ideales, debido a que muchos factores ecologicos pueden llevar a que las aves seleccionen ambientes pobres y eviten ambientes ricos. Las medidas de condicion corporal tambien pueden representar medidas convenientes de la calidad del habitat, pero para ser utiles deben ser una consecuencia y no una causa de la seleccion de habitat. Los ecologos ambientales deben tener cuidado al basarse en estudios rapidos en lugar de realizar trabajos demograficos mas laboriosos. Para incrementar la confiabilidad de nuestras medidas de calidad de habitat, debemos desarrollar nuevos metodos para abordar las suposiciones mas importantes de los indicadores no demograficos, tales como si las aves presentan distribuciones ideales en condiciones naturales, y si la variacion espacial en la condicion corporal se traduce en una adecuacion biologica diferencial.

Habitat and behavior of the common loon, a waterfowl is discussed.

Abstract: The core assumptions of critical habitat designation are a positive relationship between habitat and population size and that a minimum habitat area is required to meet a recovery target. [...]

Anthropogenic habitat alteration has long been neglected as a factor in the analysis of predictability patterns in biological communities. We tested this factor by investigating anuran leaf litter assemblages in primary and secondary forests of Tai National Park, Ivory Coast, during two years. We measured predictability of assemblage composition by analyzing correlations between the off-diagonal elements of distance matrices based on (1) species distribution, (2) environmental characteristics, and (3) geographic distance. Pairwise correlations between matrices were significant in all cases when considering data pooled across time and habitats. A different pattern emerged when data were split according to season and disturbance level (i.e., primary vs. secondary habitats). Assemblage composition in primary habitats was correlated with geographic proximity of sites exclusively, indicating otherwise stochastic recruitment from a regional species pool at the local community level. In contrast, assemblage composition in secondary habitats was predictable based on environmental parameters, not geographical proximity. This can be inferred to be the result of a strong local site filter effect (i.e., physiologically more-restrictive conditions within secondary forest habitats, especially due to an altered microclimate). Results were consistent throughout seasons. The observed transition in predictability patterns indicates that anthropogenic disturbance not only affects system descriptors, such as species richness, abundance, and diversity, but may also alter the system's dynamics. Key words: anthropogenic disturbance; habitat alteration; leaf litter anurans; predictability patterns; primary and secondary forests; rainforest; species assemblages; West Africa.

Environmental heterogeneity is considered to lead to specialization in plants and thereby contribute to the diversity of the tropical flora. The idea is examined on the basis of data on the habitat specificity of 35 western Amazonian species from the genera Protium, Crepidospermum, and Tetragastris in the monophyletic tribe Protieae mapped on a molecular-based phylogeny.

Despite much interest in the conservation of landbirds during migratory stopover periods, relatively few studies have examined spatial and temporal variation in habitat use and identified important habitats for migrating landbirds in North America. We surveyed migrant landbirds in five habitats (mature forest interior, mature forest-agricultural edge, mature suburban forest, mid-successional pole-stage forest, and early successional shrub-sapling-stage forest) in central Pennsylvania from late August to early October, 1997-1999. We used abundances of individual species and migrant guilds, species richness, and fruit availability to assess relative habitat quality for fall migrants and measured structural characteristics associated with migrant habitat use. Of 15 species that differed in abundance among habitats, species that breed in mature forest (n = 10) were typically broadly distributed among habitats during stopover, with highest abundance in edge-dominated forests (forest-agricultural edge and suburban forest) and lowest abundance in pole-stage forests. Mature-forest-breeding migrants also regularly used early successional forests, where as many individuals were recorded as in forest interior. Shrub-sapling-breeding species (n = 5) generally were more narrowly distributed among habitats and were most abundant in early successional and edge-dominated forests. We detected among-year differences in relative use of habitats by mature-forest-breeding species, which suggests that the relative quality of stopover habitats may vary from year to year. Fruit availability was highest in shrub-sapling and forest-agricultural edge habitats and was positively associated with abundance of primary frugivores in all three years, indicating that fruit may be driving habitat selection by that guild. Mature-forest-breeding migrants were positively associated with forests that had more understory vegetation and lower percentage of canopy cover (i.e. more tree-fall gaps), which suggests that migrants selected sites with greater vertical and horizontal habitat heterogeneity. Migrating shrub-sapling-breeding species were positively associated with small-diameter stems (0-2.5 cm) and negatively associated with percentage of canopy cover (i.e. characteristics of breeding habitats). Consistently high use of mature edge-dominated and early-successional forests by a wide diversity of landbird species during fall stopover indicates the potential importance of those habitats for migratory landbird conservation. Received 25 September 2003, accepted 3 May 2004.

We investigated variation of fish assemblages in response to environmental factors using Long Term Resource Monitoring Program data. Data were collected from 1993 to 2000 from five physical habitats in the unimpounded upper Mississippi River. We captured 89 species composing 18 families. Of these, 26% were fluvial specialists, 25% were fluvial dependent and 49% were generalists. The numerically dominant component of the adult fish assemblage (species accounting for >10% of total catch) accounted for 50% of the assemblage and was comprised of only three species: gizzard shad (Dorosoma cepedianum: 25%), common carp (Cyprinus carpio; 15%) and channel catfish (Ictalurus punctatus; 10%). The dominant component of the YOY fish assemblage was comprised of only two species, which accounted for 76% of the total catch: freshwater drum (Aplodinotus grunniens; 39%) and gizzard shad (37%). We used a cross-validation multivariate approach to explore how adult and young-of-the-year (YOY) assemblages varied with respect to physical habitat and environmental gradients. Furthermore, we were interested how the fish assemblages changed over time. Partial canonical correspondence analyses (pCCA) demonstrated significant effects of physical habitats. Such effects differed between young-of-the-year and adult fishes. The four main environmental gradients influencing overall assemblage structure for both age groups were river elevation, water velocity, conductivity and depth of gear deployment. Morisita's index revealed similar adult assemblage structure over time. However, the YOY assemblage present in 1995 was dissimilar from assemblages present during the other years. We speculate this is a lag effect from the backwater spawning episodes (floodpulse) that occurred with the 500-y flood in 1993. Shannon-Weiner diversity and Camargo's evenness indices were low, but stable across years for the adult assemblage, but wafted across years for the YOY assemblage.

The contestation of a resource salmon and a site Hells Gate in British Columbia, Canada in context of a rapid environmental change is analyzed. It suggested the landslides obstruction of salmon migrations, control of Hells Gate and the salmon, and their causes and consequences.

We examined home range size and habitat use of nine female northern myotis (Myotis septentrionalis) within an intensively managed forest in the central Appalachians of West Virginia. Using the 95% adaptive kernel method, we calculated a mean home range of 65 ha. Northern myotis used recent diameter-limit harvests and road corridors more than expected based on availability of these habitats. Intact forest stands and more open deferment harvested stands were used less than expected based on the availability of these habitats, although intact forest stands still constituted the overall majority of habitat used. Partial timber harvests that leave a relatively closed canopy appear to promote or improve northern myotis foraging habitat in heavily forested landscapes. However, the long-term ecological impacts on bats and other biota from this silviculturally unacceptable practice are unclear.

We used five years of mist-net-capture and point-count data to quantify avian diversity in four habitats along a 1750-m elevational gradient in the Dominican Republic. These habitats include desert thorn scrub, dry forest, pine forest, and montane broadleaf forest, which together comprise more than two-thirds of existing forest on Hispaniola. In midwinter samples we recorded 74 species of landbirds, including 22 species of latitudinal migrants and 19 endemics. The highest diversity and species richness were found in pine forest and dry forest, but the highest capture rate of individuals was in desert thorn scrub. Abundance of migrant individuals was highest in pine forest, whereas pine and montane broadleaf forest contained the highest proportion of endemic species and individuals, and more habitat specialists. Among mist-net captures, insectivorous species and individuals predominated in all habitats except in dry forest, where more omnivorous individuals were captured. A more complex pattern was found in point-count detections: insectivorous species and individuals predominated in most habitats; omnivorous species and individuals were most frequently counted in montane broadleaf and dry forest, respectively; and nectarivorous individuals were most common in desert thorn scrub. Data presented here represent the most complete quantitative record of avian abundance and distribution on Hispaniola. This study not only details the value of these four habitats to various suites of species, but also emphasizes the importance of montane broadleaf and pine forests to large numbers of Neotropical migrants and Hispaniolan endemics, some of which are narrowly restricted to these habitats. Key words: avian abundance, avian diversity, Dominican Republic, elevational gradients, Hispaniola, Neotropical migratory birds, species richness.

The sulfur nutrition of five benthic animals living in or on reductive, tidal-flat sediments has been studied by using the sulfur isotopic signatures of their soft tissues. The mean [delta][sup.34]S values (+6.1 [per thousand] to +13.8 [per thousand], relative to the Canyon Diablo troilite reference) of these animals' tissues are lower than those of many common marine animals, which have values close to those of seawater sulfate-sulfur (+21 [per thousand]). This indicates that these animals use a [sup.34]S-depleted sulfur source, which may be derived from bacterial sulfide in the sediments (less than -20[per thousand]). The animals that inhabit such sediments are adapted to an anoxic environment, where toxic hydrogen sulfide prevails. Due to the sulfide-rich habitat, benthic animals are expected to assimilate hydrogen sulfide directly during detoxification, or to prefer a diet which has a low [delta][sup.34]S signature. Variations in [delta][sup.34]S values of the sampled molluscs were fairly small, whereas migratory shrimp and fish tended to have larger variations, implying that migratory animals feed on diverse prey, while the molluscs feed on a common food, or their assimilative capacity for sulfide-sulfur does not vary among individuals. A gastropod inhabiting the surface of the reductive sediment showed a distinctively low [delta][sup.34]S value (+5.8 [per thousand] to + 6.4 [per thousand]), indicating that the animal fed on detritus from reeds and halophytes with low [delta][sup.34]S values (-19.1 [per thousand] to -2.1[per thousand]). This study suggests that some benthic animals incorporate sulfide-sulfur for their nutrition and that sulfur isotope composition can be a useful indicator in the analysis of the food habitat of animals.

We evaluated size of home ranges for male and female black bears (Ursus americanus) at 3 study sites in Washington to determine whether home-range sizes differed between sexes, study sites, and objectives of forest management. Vegetative conditions differed among study sites as a result of differences in mean annual precipitation (52, 200, and 380 cm/ year) and forest management practices. We analyzed ranked proportions of forest-cover types within error polygons for telemetry locations as measures of use, interspersion, and juxtaposition of cover types and compared these with ranks of cover types available within composite home ranges for all bears in each study site and with those available within adaptive-kernel home ranges for individual bears. Fixed-kernel estimates of home ranges for males were 3.8 times larger than those for females. Home-range size for females differed (P = 0.04) between study sites but home-range size for males did not (P = 0.79). In the study site with intensively managed and relatively undisturbed forestlands, home ranges for females were of similar size. Males and females occupied cover types different from that available within study sites and within individual home ranges. Differences among study sites for home-range sizes for females may be correlated to differences in available forage plants and cover, which may be explained by differences in annual precipitation. Behavioral differences for males and females, too, may explain differential use of forest-cover types. Hence, differences in home-range sizes between males and females and among regions may result, in part, from climatic and vegetative conditions, as well as from social status. Key words: black bear, forest-cover types, habitat use, home range, Ursus americanus, Washington

Quantifying habitat use is vital to understanding animal ecology. Herein, we contrast classification-based (i.e., animal locations are placed into habitat categories for subsequent analyses) and distance-based (i.e., distance between animal locations and habitat features are used in subsequent analyses) approaches for analyzing habitat use data. Compositional analysis (CA) and a distance-based analysis (DA) were used to quantify habitat selection of Northern Bobwhite (Colinus virginianus). We qualitatively compared the outcome of these different procedures to illustrate advantages of the DA approach. The DA approach identified edges as an important habitat feature, and location error did not alter conclusions from DA. In contrast, CA did not detect the importance of edge, and presence of location errors altered conclusions. Moreover, modeling the distribution of location error did not effectively reduce sensitivity to error within CA. Distance-based approaches to habitat analyses are not restricted to linear or point habitat features, require no explicit error handling, and permit extraction of more information from the data than classification-based analyses alone. Key words: compositional analysis; Euclidean distance; habitat analysis; habitat selection; habitat use; multivariate analysis; Northern Bobwhite; radio telemetry; telemetry bias; triangulation error.

In a field experiment, we measured the giving-up densities and activity of co-occurring American Robins (Turdus migratorius) and European Starlings (Sturnus vulgaris). Across six distances from cover, both species had lower giving-up densities near cover (safe) than away (risky). In terms of activity, both species were more active near than away from cover. Preference for cover was more pronounced for robins. Both species foraged more in the morning than in the afternoon. This pattern was more pronounced for starlings. Relative to the background environment (mowed grass), robins favored the food patches more than starlings. For starlings and robins, respectively, it took 72.6 [m.sup.2] and 382.3 [m.sup.2] of background environment to generate the same feeding activity in a 1-[m.sup.2] food patch filled with 210 mealworms (Tenebrio molitor). The greater degree of herbivory by starlings may explain the robins' greater affinity for food patches (invertebrates only) relative to the background environment (both invertebrates and plants). Key words: American Robin, European Starling, foraging theory, giving-up density, habitat preference, patch use, predation risk.

We examined winter (November-January) shorebird use at 19 sites around Humboldt Bay, California, an important site for nonbreeding shorebirds. We analyzed species richness (number of species), species densities, and incidences (presence/absence) in relation to habitat characteristics (tidal flat width, channelization, standing water, timing of tidal ebb, and sediment particle size). We included site area in analyses of incidence, and site area and substrate heterogeneity in the species richness analysis. We observed a total of 19 species, 8-16 at individual sites, and this variation correlated with substrate heterogeneity. Substrate particle size correlated positively with Sanderling (Calidris alba) incidence and negatively with American Avocet (Recurvirostra americana) incidence. Amount of standing water correlated positively with Whimbrel (Numenius phaeopus) and negatively with dowitcher (Limnodromus griseus and L. scolopaceus) incidence. Width of tidal flat correlated negatively with Whimbrel incidence. Sites at which tides ebbed earliest had higher incidences of Whimbrel and Sanderling and higher densities of Long-billed Curlew (Numenius americanus), but lower yellowlegs (Tringa melanoleuca and T. flavipes) densities. The amount of channelization correlated positively with curlew densities. These habitat relationships suggest that alteration of tidal fiats at Humboldt Bay and elsewhere in coastal habitats has the potential to adversely affect patterns of shorebird distribution. Key words: bird-habitat relationships, Charadrii, habitat characteristics, Humboldt Bay, intertidal habitats, nonbreeding distribution, shorebirds.

Previous studies suggest that Ovenbirds (Seiurus aurocapillus) are area sensitive and apparently avoid forest edges. In 1999 and 2000, we used radiotelemetry to investigate how breeding male Ovenbirds respond to forest edges. Twenty-one males with home ranges abutting edges of seven forest fragments surrounded by agriculture were tracked for an average of two weeks. We found that sightings of males were situated 8 [+ or -] 10 m closer to edges than random locations within each home range. However, the mean time of day for edge sightings (1139 hours, 95% CI = 1052-1227 hours) occurred significantly later than the mean for sightings in the interior of forest fragments (0936 hours, 95% CI = 0856-1016 hours). That indicates that previous studies focusing on morning singing locations to delineate home-range use have likely underestimated use of edges by birds. Habitat characteristics also varied in relation to edges. Forest canopy was lower, shrubs were denser, leaf-litter thicker, and soils dryer near edges than in the portion of home ranges facing the interior of forest fragments. Arthropod biomass varied little in relation to edges, except biomass of larvae, which was greatest at edges. Boreal forest edges abutting agricultural fields do not appear to reduce habitat use or quality for breeding male Ovenbirds, and so we suggest that the generalized association between area sensitivity and edge avoidance for Ovenbirds in forest fragments be reassessed. Received 4 February 2002, accepted 1 October 2002.

Abstract: The girellid fish Girella leonina (Richardson) and the holocentrid Myripristis murdjan (Forsskal) are reported for the first time for the Hawaiian Islands from underwater photographs taken at Midway Atoll. [...]

Abstract. -- A population of Coluber constrictor flaviventris was surveyed in both relic and disturbed Blackland Prairie habitats during the spring, summer and fall of 1999 and 2000 at Cedar [...]

Research shows that major temporal changes in an estuarine fish assemblage are a function of monthly and spring/neap differences with no influence from the ebb/flood tides. Data indicate that trophic patterns are stronger and consistent than taxonomic trends.

Research has been conducted on the evolution of the ecological specialization in a landscape with the discrete habitat types connected by migration. Results indicate that specialization on a single habitat evolves with the intermediate migration rates and the generalist species evolves with the low and large rates of movements between the habitats.

Lewis's Woodpecker (Melanerpes lewis) has been characterized as a 'burn specialist' because of its preference for nesting within burned pine forests. No prior study, however, has demonstrated the relative importance of crown-burned forests to this woodpecker species by examining its reproductive success in different forest types. We studied breeding Lewis's Woodpeckers in cottonwood (Populus fremontii) riparian forest patches of Colorado and crown-burned ponderosa pine (Pinus ponderosa) forests of Idaho to compare their reproductive success, productivity, and potential source-sink status in the two forest types. Daily nest survival rates were significantly lower in cottonwood compared to burned pine forests. Nesting success was 46% (n = 65) in cottonwood forests and 78% (n = 283) in burned pine forests. Proportion of nests destroyed by predators was significantly higher in cottonwood forests (34%) compared to burned pine forests (16%). We consistently found crown-burned forests to be potential source habitat, whereas cottonwood riparian sites were more often concluded to be potential sink habitat. Cottonwood riparian forests were surrounded primarily by an agricultural landscape where the composition and abundance of nest predators was likely very different than the predator assemblage occupying a large-scale burn in a relatively natural landscape. Conversion of riparian and adjacent grassland landscapes to agriculture and prevention of wildfire in ponderosa pine forests have likely reduced nesting habitat for this species. Prescribed understory fire is the prevailing management tool for restoring ponderosa pine ecosystems. Conditions created by crown fire may be equally important in maintaining ponderosa pine systems and conserving nesting habitat for the Lewis's Woodpecker. Key words: crown-burned forests, Lewis's woodpecker, Melanerpes lewis, nest success, Pinus ponderosa, Populus fremontii, source-sink habitats.

Research has been conducted on the relationship between the habitat factors (depth, sediment grain size and latitude) and the benthic infaunal assemblage distribution on a coastal shelf. The examination of this relationship has been carried out via a Q-mode cluster analysis to define the station groups with similar species composition and to investigate the differences between physical habitat attributes among those station groups.