This study examined the influence of insects (mosquitoes and oestrids) on the distribution, microhabitat choice, and behavior of a population of mountain caribou. The study was conducted in the Burwash area of southwestern Yukon Territory during the summers of 1982 and 1983. Mosquito density, the presence or absence of oestrids, and the distribution, microhabitat use, and insect-avoidance behavior of the caribou were observed. Seasonal activity budgets for caribou were calculated. Mosquitoes became active in mid-June. Activity decreased with altitude, and at the highest altitudes (2000 m) the number of mosquitoes was negligible. Snow patches and exposed windy ridges had fewer mosquitoes than did open tundra. The oestrid season began in late June and lasted until early August. Oestrids were widespread throughout the study area and were present in all microhabitats. Caribou reduced harassment by mosquitoes by their altitudinal movements and use of microhabitat. Oestrids influenced activity budgets of caribou, acting to decrease feeding and resting time and to increase the time spent standing and moving.

North American populations of aerial insectivorous birds are in steep decline. Aerial insectivores (AI) are a group of bird species that feed almost exclusively on insects in flight, and include swallows, swifts, nightjars, and flycatchers. The causes of the declines are not well understood. Indeed, it is not clear when the declines began, or whether the declines are shared across all species in the group (e.g., caused by changes in flying insect populations) or specific to each species (e.g., caused by changes in species’ breeding habitat). A recent study suggested that population trends of aerial insectivores changed for the worse in the 1980s. If there was such a change point in trends of the group, understanding its timing and geographic pattern could help identify potential causes of the decline. We used a hierarchical Bayesian, penalized regression spline, change point model to estimate group-level change points in the trends of 22 species of AI, across 153 geographic strata of North America. We found evidence for group-level change points in 85% of the strata. Change points for flycatchers (FC) were distinct from those for swallows, swifts and nightjars (SSN) across North America, except in the Northeast, where all AI shared the same group-level change points. During the 1980s, there was a negative change point across most of North America, in the trends of SSN. For FC, the group-level change points were more geographically variable, and in many regions there were two: a positive change point followed by a negative change point. This group-level synchrony in AI population trends is likely evidence of a response to a common environmental factor(s) with similar effects on many species across broad spatial extents. The timing and geographic patterns of the change points that we identify here should provide a spring-board for research into the causes behind aerial insectivore declines.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Smith, Adam C., marie-Anne r. Hudson, Constance Downes, and Charles m. Francis. 2014. Estimating breeding bird survey trends and annual indices for Canada: how do the new hierarchical Bayesian estimates differ from previous estimates? Canadian Field-Naturalist 128(2): 119-134.Canadian data from the North American Breeding Bird Survey (BBS) provide information on the population status and trends for over 300 species that regularly breed in Canada. Since the first assessments were made in the mid-1970s, both the dataset and the suite of statistical tools and techniques available to researchers have grown. As a result, Canadian BBS trend estimates have been derived from numerous statistical models. Because the BBS data are relatively complex, different statistical models can generate different trend and status estimates from the same data. In 2013, Environment Canada's Canadian wildlife Service began producing BBS status and trend estimates using a hierarchical Bayesian model. To give users of BBS trends and annual indices of abundance a better understanding of these estimates, we demonstrate and explain some of the similarities and differences between the new hierarchical Bayesian estimates and those from the previous model; discuss the philosophical and inferential consequences of estimating trends with the new model; and describe how the hierarchical Bayesian model differs from the model currently used in the united States. overall, trends and annual indices from the new model are generally similar to estimates from the previous model; however, they are more precise, less variable among years, better represent the spatial variation across Canada in population status, and allow for more intuitive and useful assessments of uncertainty.

Recent population trends of Ontario's forest birds were assessed by integrating results across 8 bird surveys to provide an estimate of trend status for all of Ontario, and for 2 forested regions of Ontario separately. Surveys with mid-and longterm trends were relied on most extensively in this assessment. Comparison of the first and second Breeding Bird Atlases was especially important for estimating trends in northern forests, but overall reliability of status assessments in the north was considered poor due to limited coverage and significant potential for bias. Trends of most forest birds were stable or positive at the Ontario-wide scale, with trends at least as positive as forest birds elsewhere in North America, and showing more positive trends overall than birds of agricultural landscapes. Nevertheless, individual species trends ranged from large declines to large increases, and several forest birds have been added to Species at Risk lists largely because of population declines. There were few differences in trend status among forest birds grouped by habitat association or migratory guild, although all 5 aerial insectivore species have declined. Better monitoring coverage of the boreal will be needed if improved reliability of trends is desired in the near future.Key words: Ontario, forest birds, boreal forest, population trend, bird surveys, monitoring reliability RÉSUMÉLes fluctuations récentes des populations d' oiseaux forestiers de l'Ontario ont été évaluées au moyen de l'intégration des résultats de 8 relevés d' oiseaux pour produire un estimé de la tendance actuelle pour tout l'Ontario ainsi que particulière-ment pour 2 régions forestières de la province. Les relevés indiquant les fluctuations à moyen et à long terme ont fait l' objet d'une utilisation plus poussée pour cette évaluation. La comparaison entre le premier et le second atlas des oiseaux nicheurs a été particulièrement importante pour pouvoir estimer les fluctuations dans les forêts boréales, mais la fiabilité générale des tendances actuelles dans le nord de la province a été jugée faible compte tenu de la couverture restreinte et du potentiel significatif de biais. Les fluctuations de la plupart des populations d' oiseaux forestiers se sont révélées être stables ou positives pour l' ensemble de la province, ces fluctuations étant au moins aussi positives par rapport aux oiseaux forestiers ailleurs en Amérique du Nord et elles étaient encore plus positives dans l' ensemble par rapport aux oiseaux des milieux agricoles. Néanmoins, les fluctuations des espèces individuelles variaient entre des déclins importants et des accroissements majeurs et quelques oiseaux forestiers ont été ajoutés à la liste des espèces en péril principalement suite à un déclin des populations. Peu de différence a été relevée pour ce qui est des tendances chez les oiseaux forestiers regroupés en fonction de leur habitat ou de leur regroupement migratoire, même si 5 espèces insectivores se nourrissant en vol sont en déclin. Une meilleure étude des territoire...