Ecological traps arise when anthropogenic change creates habitat that appears suitable but when selected reduces the fitness of an individual. We evaluated whether riparian habitat within the drawdown zone of the Arrow Lakes Reservoir, British Columbia, creates an ecological trap for Yellow Warblers ( Setophaga petechia (L., 1766)) by investigating habitat preferences and the fitness consequences of habitat selection decisions. Preferences were inferred by examining how habitat variables influenced settlement order, and comparing habitat at nest sites and random locations. Males preferred to settle in territories with more riparian shrub and tree cover, higher shrub diversity, and less high canopy cover. Females built nests in taller shrubs surrounded by a greater density of shrub stems. Habitat preferences were positively associated with fitness: nest sites in taller shrubs surrounded by higher shrub-stem densities were more likely to avoid predation and fledge young, whereas territories with more riparian cover, higher shrub diversity, and less high canopy cover had higher annual productivity. We therefore found no evidence that riparian habitat affected by reservoir operations functions as an ecological trap. Current habitat selection decisions may be associated with fitness because Yellow Warblers are adapted to breeding in a heterogeneous environment subject to periodic flooding.

Territorial clustering within larger, continuous patches of seemingly appropriate habitat could indicate that a species has additional, finer scale habitat requirements. Studying fine-scale (e.g., territory-level) habitat selection using methods that elucidate individual preferences may allow us to identify resources that influence species distributions. We examined breeding territory selection in the sagebrush Brewer's Sparrow (Spizella breweri Cassin, 1856) at the northern extent of its range to test for influences on fine-scale habitat selection. We used an information-theoretic approach to evaluate models relating a suite of vegetation characteristics to breeding habitat selection. We employed two methods: (1) assessment of patch occupancy at a territory scale and (2) examination of individual decisions relating to settlement and dispersal. We found that patch occupancy was most consistently predicted by models that included the cover of big sagebrush (Artemisia tridentata Nutt.) with the greatest likelihood of occupancy at 20%-25% cover. However, assessment of settlement and dispersal decisions did not identify additional fine-scale preferences for other vegetation characteristics. Vegetation cover also did not influence breeding success, indicating that within the vegetation range found in Brewer's Sparrow territory clusters, there is little benefit in basing individual settlement or dispersal decisions on vegetation cover. Résumé : Le regroupement d'un territoire avec des taches d'habitat en apparence appropriées, mais plus grandes et continues, pourrait indiquer qu'une espèce possède des besoins additionnels d'habitat à une échelle plus fine. L'étude de la sélection d'habitat à échelle fine (par ex., au niveau du territoire) en utilisant des méthodes qui mettent en lumière les préférences individuelles permet peut-être d'identifier les ressources qui influencent la répartition des espèces. Nous examinons la sélection du territoire de reproduction chez le bruant de Brewer des armoises (Spizella breweri Cassin, 1856) à la limite boréale de son aire de répartition afin de vérifier les influences sur la sélection d'habitat à échelle fine. Nous utilisons une approche basée sur la théorie de l'information afin d'évaluer des modèles qui relient une série de caractéristiques de la végétation à la sélection de l'habitat de reproduction. Nous employons deux méthodes, (1) une évaluation de l'occupation des taches à l'échelle du territoire et (2) un examen des décisions individuelles concernant l'établissement et la dispersion. Ce sont les modèles qui incluent la couverture de la grande armoise (Artemisia tridentata Nutt.) qui prédisent l'occupation des taches de la façon la plus constante; la plus grande probabilité d'occupation se situe à une couverture de 20 % -25 %. L'évaluation des décisions d'établissement et de dispersion n'a pas, cependant, identifié de préférences additionnelles à échelle fine pour d'autres caractéristiques de la végétation. De plus, la couverture végétale n'influence pas le succès de la rep...

We used plasma metabolite analysis to estimate variation in fattening rate in four neotropical migratory songbirds utilising riparian habitat at a dam-impacted stopover in British Columbia, Canada. Our study suggests that although hydroelectric dam operations influence water levels this does not significantly impact fattening rates of birds using these habitats.

No abstract