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Habitat Relationships (habitat + relationships)
Selected AbstractsOne Hundred Fifty Years of Change in Forest Bird Breeding Habitat: Estimates of Species DistributionsCONSERVATION BIOLOGY, Issue 6 2005LISA A. SCHULTE aptitud del hábitat; ecología aviar; ecología de paisaje; planificación de conservación Abstract:,Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant change. We propose pre-Euro-American settlement as an alternative baseline for assessing changes in bird populations. We evaluated the amount, quality, and distribution of breeding bird habitat during the mid-1800s and early 1990s for three forest birds: the Pine Warbler (Dendroica pinus), Blackburnian Warbler (D. fusca), and Black-throated Green Warbler (D. virens). We constructed models of bird and habitat relationships based on literature review and regional data sets of bird abundance and applied these models to widely available vegetation data. Original public-land survey records represented historical habitat conditions, and a combination of forest inventory and national land-cover data represented current conditions. We assessed model robustness by comparing current habitat distribution to actual breeding bird locations from the Wisconsin Breeding Bird Atlas. The model showed little change in the overall amount of Pine Warbler habitat, whereas both the Blackburnian Warber and the Black-throated Green Warbler have experienced substantial habitat losses. For the species we examined, habitat quality has degraded since presettlement and the spatial distribution of habitat shifted among ecoregions, with range expansion accompanying forest incursion into previously open habitats or the replacement of native forests with pine plantations. Sources of habitat loss and degradation include loss of conifers and loss of large trees. Using widely available data sources in a habitat suitability model framework, our method provides a long-term analysis of change in bird habitat and a presettlement baseline for assessing current conservation priority. Resumen:,La evaluación de tendencias de las poblaciones de aves requiere de datos de referencia. En Norte América, los primeros datos disponibles de poblaciones son del final de la década de 1960. Sin embargo, las condiciones de los bosques en los estados de los Grandes Lagos (E.U.A.) han experimentado sucesión desde que la región fue talada en los inicios del siglo veinte, y se espera que las poblaciones de aves hayan experimentado cambios concomitantes. Proponemos que se considere al período previo a la colonización euro americana como referencia alternativa para evaluar los cambios en las poblaciones de aves. Evaluamos la cantidad, calidad y distribución del hábitat para reproducción de tres especies de aves de bosque (Dendroica pinus, D. fusca y D. virens) a mediados del siglo XIX e inicios del XX. Construimos modelos de las relaciones entre las aves y el hábitat con base en la literatura y conjuntos de datos de abundancia de aves y los aplicamos a los datos de vegetación ampliamente disponibles. Los registros topográficos de tierras públicas originales representaron las condiciones históricas del hábitat, y una combinación de datos del inventario forestal y de cobertura de suelo representaron las condiciones actuales. Evaluamos la robustez del modelo mediante la comparación de la distribución de hábitat actual con sitios de reproducción de aves registrados en el Wisconsin Breeding Bird Atlas. El modelo mostró poco cambio en la cantidad total de hábitat de Dendroica pinus, mientras que tanto D. fusca como D. virens han experimentado pérdidas sustanciales de hábitat. Para las especies examinadas, la calidad del hábitat se ha degradado desde antes de la colonización y la distribución espacial del hábitat cambió entre ecoregiones, con la expansión del rango acompañando la incursión de bosques en hábitats anteriormente abiertos o el reemplazo de bosques nativos con plantaciones de pinos. Las fuentes de pérdida y degradación de hábitats incluyen la pérdida de coníferas y de árboles grandes. Mediante la utilización de fuentes de datos ampliamente disponibles en un modelo de aptitud de hábitat, nuestro método proporciona un análisis a largo plazo de los cambios en el hábitat de aves y una referencia precolonización para evaluar prioridades de conservación actuales. [source] Where do Swainson's hawks winter?DIVERSITY AND DISTRIBUTIONS, Issue 5 2008Satellite images used to identify potential habitat ABSTRACT During recent years, predictive modelling techniques have been increasingly used to identify regional patterns of species spatial occurrence, to explore species,habitat relationships and to aid in biodiversity conservation. In the case of birds, predictive modelling has been mainly applied to the study of species with little variable interannual patterns of spatial occurrence (e.g. year-round resident species or migratory species in their breeding grounds showing territorial behaviour). We used predictive models to analyse the factors that determine broad-scale patterns of occurrence and abundance of wintering Swainson's hawks (Buteo swainsoni). This species has been the focus of field monitoring in its wintering ground in Argentina due to massive pesticide poisoning of thousands of individuals during the 1990s, but its unpredictable pattern of spatial distribution and the uncertainty about the current wintering area occupied by hawks led to discontinuing such field monitoring. Data on the presence and abundance of hawks were recorded in 30 × 30 km squares (n = 115) surveyed during three austral summers (2001,03). Sixteen land-use/land-cover, topography, and Normalized Difference Vegetation Index (NDVI) variables were used as predictors to build generalized additive models (GAMs). Both occurrence and abundance models showed a good predictive ability. Land use, altitude, and NDVI during spring previous to the arrival of hawks to wintering areas were good predictors of the distribution of Swainson's hawks in the Argentine pampas, but only land use and NDVI were entered into the model of abundance of the species in the region. The predictive cartography developed from the models allowed us to identify the current wintering area of Swainson's hawks in the Argentine pampas. The highest occurrence probability and relative abundances for the species were predicted for a broad area of south-eastern pampas that has been overlooked so far and where neither field research nor conservation efforts aiming to prevent massive mortalities has been established. [source] Spatial metrics and methods for riverscapes: quantifying variability in riverine fish habitat patternsENVIRONMETRICS, Issue 5 2009Céline Le Pichon Abstract Defining the optimal configuration of all habitats required during a life cycle, called vital habitat, is a necessary step for effective management of riverine fishes and restoration of river habitats. Landscape ecology provides many metrics and methods to study the composition and configuration of habitats, but they need to be adapted for fishes in river environments or riverscapes. For example, hydrographic distance seems more appropriate than Euclidean distance for measuring distances between vital habitats in riverscapes. We adapted some metrics to assess habitats patterns of a threatened cyprinid species (Barbus barbus) for natural and artificial riverscapes of the Seine river, France. Composition metrics provided essential quantification of the relative abundance of the vital habitats, whereas configuration metrics were relevant to quantify their spatial arrangement and spatial relationships. Nearest-neighbor hydrographic distance was useful to evaluate the influence of flow variability in the natural riverscape, but was not relevant to discriminate the artificial riverscape from the natural one. Conversely, a proximity index revealed high fragmentation in the artificial riverscape. Spatial habitat relationships between feeding and resting habitats, evaluated with a moving window analysis, provided a map of daily activity patches and emphasized the gaps in the biological continuity of the riverscape. The spatial metrics and methods we adapted to the particularities of the Seine river allowed us to detect natural and artificial variability in fish habitat patterns. They should help in evaluating impacts of habitat alteration and isolation and prioritize preservation and restoration policies in human-impacted rivers. Copyright © 2008 John Wiley & Sons, Ltd. [source] Winter selection of landscapes by woodland caribou: behavioural response to geographical gradients in habitat attributesJOURNAL OF APPLIED ECOLOGY, Issue 5 2008Daniel Fortin Summary 1Understanding animal,habitat relationships is central to the development of strategies for wildlife management and conservation. The availability of habitat attributes often changes along latitudinal and longitudinal axes, and animals may respond to those changes by adjusting their selection. We evaluated whether landscape selection by forest-dwelling woodland caribou Rangifer tarandus caribou varied along geographical gradients in habitat attributes. 2Centroids (n = 422) of track networks made by caribou in winter were recorded during aerial surveys conducted over 161 920 km2 of boreal forest in Québec, Canada. Autologistic models were estimated by comparing the characteristics of landscapes (201 km2) centred on each centroid to an equal number of randomly located landscapes, with an autocovariate controlling for the non-independence among caribou locations. 3The availability of habitat attributes varied along longitudinal and latitudinal gradients, and caribou altered their landscape selection with respect to those gradients. 4Information Theory provided substantial support for only one model. The model revealed that the probability of occurrence of caribou increased with the abundance of conifer forests over most of the study region, but this positive response gradually became negative towards the southern portion of the region. The association between caribou and lichens changed from being negative west of the study region to being positive in the eastern part. Availability of landscapes dominated by lichen decreased from west to east. Finally, caribou generally displayed an aversion to areas with high road density, a negative association that became positive in the southern part of the study region. 5Synthesis and applications. Under current legislation in Canada, the critical habitat of woodland caribou must be defined, and then protected. Our autoregressive models can help to identify landscapes to prioritize conservation efforts. The probability of occurrence of caribou was related to different landscape characteristics across their range, which implies that the typical habitat of woodland caribou differs spatially. Such behavioural plasticity could be problematic for defining critical habitat, but we showed that spatial variation in landscape selection was organized along geographical gradients. Our study illustrates how geographical trends in habitat selection can guide management and conservation decisions. [source] Microhabitat relationships among five lizard species associated with granite outcrops in fragmented agricultural landscapes of south-eastern AustraliaAUSTRAL ECOLOGY, Issue 2 2010DAMIAN R. MICHAEL Abstract A fundamental part of developing effective biodiversity conservation is to understand what factors affect the distribution and abundance of particular species. However, there is a paucity of data on ecological requirements and habitat relationships for many species, especially for groups such as reptiles. Furthermore, it is not clear whether habitat relationships for particular species in a given environment are transferable to other environments within their geographical range. This has implications for the type of ,landscape model' used to guide management decisions in different environments worldwide. To test the hypothesis that species-specific habitat relationships are transferable to other environments, we present microhabitat models for five common lizard species from a poorly studied habitat , insular granite outcrops, and then compared these relationships with studies from other environments in south-eastern Australia. We recorded twelve species from five families, representing 699 individuals, from 44 outcrops in the south-west slopes of New South Wales. Five lizard species were abundant and accounted for 95% of all observations: Egernia striolata, Ctenotus robustus, Cryptoblepharus carnabyi, Morethia boulengeri and Carlia tetradactyla (Scincidae). Linear regression modelling revealed suites of different variables related to the abundance patterns of individual species, some of which were broadly congruent with those measured for each species in other environments. However, additional variables, particular to rocky environments, were found to relate to reptile abundance in this environment. This finding means that species' habitat relationships in one habitat may not be readily transferable to other environments, even those relatively close by. Based on these data, management decisions targeting reptile conservation in agricultural landscapes, which contain rocky outcrops, will be best guided by landscape models that not only recognize gradients in habitat suitability, but are also flexible enough to incorporate intraspecies habitat variability. [source] | ||||||||||