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When planning abundance surveys, the impact of search intensity on the quality of the density estimates is rarely considered. We constructed a time‐budget modeling framework for abundance surveys using principles from optimal foraging theory. We link search intensity to the number of sample units surveyed, searcher detection probability, the number of detections made, and the precision of the estimated population density. This framework allowed us to determine how a searcher should behave to produce optimized density estimates. Using data collected from quadrat and removal surveys of zebra mussels (Dreissena polymorpha) in central Minnesota, we applied this framework to evaluate potential improvements. We found that by tuning searcher behavior, density estimates from removal surveys of zebra mussels could be improved by up to 60% in some cases, without changing the overall survey time. Our framework also predicts a critical population density where the best survey method switches from removal surveys at low densities to quadrat surveys at high densities, consistent with past empirical work. In addition, we provide simulation tools to apply this form of analysis to a number of other commonly used survey designs. Our results provide insights into how to improve the performance of many survey methods in high‐density environments by either tuning searcher behavior or decoupling the estimation of population density and detection probability. [ABSTRACT FROM AUTHOR]

Although several studies have evaluated fisher (Pekania pennanti (Erxleben, 1777)) selection of den structures across their natural range, the role of other nearby trees with suitable cavities that can be used by female fishers for subsequent maternal dens has not been explored. We used conditional logistic regression to describe selection of natal and maternal dens by female fishers in northern Minnesota, United States, and to determine if the density of other cavity trees surrounding a specific tree influences this selection. Our results indicate that cavity density was an important predictor of whether a tree was used as a den site by female fishers. The apparent condition (i.e., live, declining, or dead) and diameter at breast height of the cavity tree itself were also important for selection. These results affirm the need to retain large-diameter cavity trees, illustrate the potential benefits of retaining them in high-density patches, and caution against creating a landscape with highly dispersed denning options. Key words: habitat selection, den structures, fisher, Pekania pennanti, cavity retention. Bien que plusieurs etudes aient evalue le choix du pekan (Pekania pennanti (Erxleben, 1777)) quant aux structures qui lui servent de taniere dans son aire de repartition naturelle, le role des autres arbres voisins avec des cavites appropriees pouvant etre utilisees subsequemment par les pekans femelles comme taniere maternelle n'a pas ete explore. Nous avons utilise la regression logistique conditionnelle pour caracteriser le choix des tanieres natales et maternelles par les pekans femelles dans le nord du Minnesota, aux Etats-Unis, et determiner si la densite des autres arbres creux voisins d'un arbre particulier influence ce choix. Nos resultats indiquent que la densite des cavites est un important predicteur pour determiner si un arbre creux a ete utilise comme site pour une taniere par les pekans femelles. La condition apparente (c.-a-d. vivant, deperissant ou mort) et le diametre a hauteur de poitrine de l'arbre creux lui-meme etaient des facteurs determinants dans le choix. Ces resultats confirment le besoin de conserver des arbres creux de gros diametre, illustrent les benefices potentiels de les conserver dans des parcelles de foret dense et incitent a ne pas creer de paysages ou les possibilites de trouver une taniere sont tres dispersees. Mots-cles: choix de l'habitat, structures pouvant servir de taniere, pekan, Pekania pennanti, retention de cavites., Introduction The fisher (Pekania [formerly Martes] pennanti (Erxleben, 1777)) is a medium-sized carnivore native to the forests of North America whose pre-European distribution encompassed much of the northeastern and western [...]

Abundance surveys are commonly used to estimate plant or animal densities and frequently require estimating detection probabilities to account for imperfect detection. The estimation of detection probabilities requires additional measurements that take time, potentially reducing the efficiency of the survey when applied to high-density populations. We conducted quadrat, removal, and distance surveys of zebra mussels (Dreissena polymorpha) in three central Minnesota lakes and determined how much survey effort would be required to achieve a pre-specified level of precision for each abundance estimator, allowing us to directly compare survey design efficiencies across a range of conditions. We found that the required sampling effort needed to achieve our precision goal depended on both the survey design and population density. At low densities, survey designs that could cover large areas but with lower detection probabilities, such as distance surveys, were more efficient (i.e., required less sampling effort to achieve the same level of precision). However, at high densities, quadrat surveys, which tend to cover less area but with high detection rates, were more efficient. These results demonstrate that the best survey design is likely to be context-specific, requiring some prior knowledge of the underlying population density and the cost/time needed to collect additional information for estimating detection probabilities. [ABSTRACT FROM AUTHOR]

Sandhill Cranes Antigone canadensis exhibit delayed sexual maturity and breeding, and therefore juvenile Cranes searching for suitable territories to occupy have different ecological constraints on movements than adults, which must defend a territory and raise young. We used fine‐scale GPS telemetry data to characterize and compare movements of adult and juvenile Cranes near the boundary between two populations in Minnesota, USA, from arrival on natal areas in the spring until staging prior to autumn migration. Juvenile and adult Cranes had marked differences in movement patterns throughout the breeding season. Juveniles were more likely than adults to display long‐distance movements: they revisited areas less frequently throughout the breeding season and they had lower average residence times. [ABSTRACT FROM AUTHOR]

‘Species distribution modeling’ was recently ranked as one of the top five ‘research fronts’ in ecology and the environmental sciences by ISI's Essential Science Indicators, reflecting the importance of predicting how species distributions will respond to anthropogenic change. Unfortunately, species distribution models (SDMs) often perform poorly when applied to novel environments. Compounding on this problem is the shortage of methods for evaluating SDMs (hence, we may be getting our predictions wrong and not even know it). Traditional methods for validating SDMs quantify a model's ability to classify locations as used or unused. Instead, we propose to focus on how well SDMs can predict the characteristics of used locations. This subtle shift in viewpoint leads to a more natural and informative evaluation and validation of models across the entire spectrum of SDMs. Through a series of examples, we show how simple graphical methods can help with three fundamental challenges of habitat modeling: identifying missing covariates, non‐linearity, and multicollinearity. Identifying habitat characteristics that are not well‐predicted by the model can provide insights into variables affecting the distribution of species, suggest appropriate model modifications, and ultimately improve the reliability and generality of conservation and management recommendations. [ABSTRACT FROM AUTHOR]

Animal diel activity patterns can aid understanding of (a) how species behaviourally adapt to anthropogenic and natural disturbances, (b) mechanisms of species co‐existence through temporal partitioning, and (c) community or ecosystem effects of diel activity shifts. Activity patterns often vary spatially, a feature ignored by the kernel density estimators (KDEs) currently used for estimating diel activity. Ignoring this source of heterogeneity may lead to biased estimates of uncertainty and misleading conclusions regarding the drivers of diel activity. Thus, there is a need for more flexible statistical approaches for estimating activity patterns and testing hypotheses regarding their biotic and abiotic drivers. We illustrate how trigonometric terms and cyclic cubic splines combined with hierarchical models can provide a valuable alternative to KDEs. Like KDEs, these models accommodate circular data, but they can also account for site‐to‐site and other sources of variability, correlation amongst repeated measures, and variable sampling effort. They can also more readily quantify and test hypotheses related to the effects of covariates on activity patterns. Through empirical case studies, we illustrate how hierarchical models can quantify changes in activity levels due to seasonality and in response to biotic and abiotic factors (e.g. anthropogenic stressors and co‐occurrence). We also describe frequentist and Bayesian approaches for quantifying site‐specific (conditional) and population‐averaged (marginal) activity patterns. We provide guidelines and tutorials with detailed step‐by‐step instructions for fitting and interpreting hierarchical models applied to time‐stamped data, such as those recorded by camera traps and audio recorders. We conclude that this approach offers a viable, flexible, and effective alternative to KDEs when modelling animal activity patterns. [ABSTRACT FROM AUTHOR]