No abstract

Clearcutting of forests results in habitats that structurally resemble grasslands and so may act as ecological traps for grassland birds. Several studies have implicated predation as the factor that decreases the number of offspring, but few have examined performance at other breeding stages. Consistent with a passive ecological trap, Mountain Bluebirds (Sialia currucoides (Bechstein, 1798)) that settled in clearcuts in central British Columbia did not differ in age or quality from adults in grasslands. Nest building and laying date of the first egg did not differ between habitats, suggesting an equal propensity for settling in each habitat. In clearcuts, however, the body condition of female parents was lower, and they abandoned their nests more often in harsh weather. This higher total clutch loss in clearcuts meant that seasonal production of fledglings per female was 13% less in clearcuts. Furthermore, fledglings in grasslands weighed 4% more and female fledglings had plumage with shorter (UV-shifted) wavelengths (hence greater ornamentation) than those in clearcuts, suggesting that they were also of better quality. Thus, predation rates were not the cause of reduced reproduction in clearcuts; rather, our results suggest that lower prey abundance was linked to nest abandonment in harsh weather and reduced both the number and quality of offspring in those habitats.

Clear-cutting of forests results in early successional stages that resemble grasslands, and grassland birds such as Mountain Bluebirds (Sialia currucoides) may settle in these anthropogenically created habitats to breed. Our objective was to determine if parent bluebirds provisioned offspring differently, in terms of amount and quality of prey, in clear-cuts versus grasslands, and how this related to fledgling production. We placed microcameras inside 92 nestboxes during two breeding seasons to film parental food deliveries at sites in central British Columbia. At the young nestling stage (< 5 d old), there were no significant differences in terms of provisioning rate or the type of prey delivered. Neither the abundance of perches in the habitat nor parental traits such as age or plumage brightness were associated with provisioning. When nestlings were older, parents in clear-cuts delivered slightly larger prey and diets with proportionately more larvae and spiders, the most nutritious taxa. However, delivery rates were 21% higher in grasslands than in clearcuts. Fledglings in clear-cuts had lighter body mass than those in grasslands, suggesting that the high nutrient content of prey in clearcuts could not compensate for the lower deliveries. Thus, parents in grasslands seem more able to meet the energy demands of large nestlings by incorporating diverse insect taxa into their diet. Fréquence de nourrissage et type de proies du Merlebleu azuré dans les prairies et les parterres de coupe totale RÉSUMÉ. À la suite de coupes totales, les premiers stades de succession végétale ressemblent à des prairies naturelles, et les oiseaux de prairie, comme le Merlebleu azuré (Sialia currucoides), peuvent nicher dans ces parterres artificiellement créés. Notre objectif était de déterminer si les merlebleus adultes établis dans des parterres de coupe totale nourrissaient leurs oisillons différemment de ceux établis dans des prairies, en termes de quantité et de qualité de proies, et de comparer la production de jeunes. Nous avons placé des microcaméras à l'intérieur de 92 nichoirs au cours de deux saisons de nidification pour filmer le nourrissage des oisillons par les adultes à des sites localisés dans le centre de la Colombie-Britannique. Au stade précoce des oisillons (âgés de < 5 jours), il n'y avait pas de différence significative de la fréquence de nourrissage ni du type de proie offerte. Ni la quantité de perchoirs dans l'habitat, ni les traits parentaux tels que l'âge ou la brillance du plumage, n'ont contribué à la fréquence de nourrissage. Lorsque les oisillons étaient plus âgés, les parents de parterres de coupe leur ont apporté des proies légèrement plus grosses, et leur régime alimentaire comportait proportionnellement plus de larves et d'araignées (le taxon le plus nutritionnel). Toutefois, la fréquence de nourrissage était plus élevée (de 21 %) dans les prairies comparativement aux parterres de coupe. Les jeunes nés dans les parterres de coupe avaient un poids plus faible que ceux nés dans les prairies, ce qui la...

Understanding lead exposure pathways is a priority because of its ubiquitous presence in the environment as well as the potential health risks. We aimed to identify potential lead sources and pathways of lead exposure, including long-range transport, and the magnitude of exposure in Arctic and subarctic communities. A scoping review strategy and screening approach was used to search literature from January 2000 to December 2020. A total of 228 academic and grey literature references were synthesised. The majority of these studies (54%) were from Canada. Indigenous people in Arctic and subarctic communities in Canada had higher levels of lead than the rest of Canada. The majority of studies in all Arctic countries reported at least some individuals above the level of concern. Lead levels were influenced by a number of factors including using lead ammunition to harvest traditional food and living in close proximity to mines. Lead levels in water, soil, and sediment were generally low. Literature showed the possibility of long-range transport via migratory birds. Household lead sources included lead-based paint, dust, or tap water. This literature review will help to inform management strategies for communities, researchers, and governments, with the aim of decreasing lead exposure in northern regions.