The COVID-19 pandemic resulted in extraordinary declines in human mobility, which, in turn, may affect wildlife. Using records of more than 4.3 million birds observed by volunteers from March to May 2017-2020 across Canada and the United States, we found that counts of 66 (80%) of 82 focal bird species changed in pandemic-altered areas, usually increasing in comparison to prepandemic abundances in urban habitat, near major roads and airports, and in counties where lockdowns were more pronounced or occurred at the same time as peak bird migration. Our results indicate that human activity affects many of North America's birds and suggest that we could make urban spaces more attractive to birds by reducing traffic and mitigating the disturbance from human transportation after we emerge from the pandemic.

Reproduction and biochemical indicators (vitamin A, ethoxyresorufin‐O‐deethylase [EROD], highly carboxylated porphyrins) of contaminant effects, and concentrations of organochlorine residues were measured in tree swallows from wetlands within the watersheds of the Great Lakes and the St. Lawrence River, USA and Canada. To assess the vitamin A sources in the tree swallow diets, insects were collected, by ligature, from nestlings at four of these sites. Diet samples were analyzed for retinol and α‐ and β‐carotene. Marked differences were found in chlorinated hydrocarbon residues in eggs and nestlings among sites; however, we did not find any significant differences in hatching or fledging success. The maximum polychlorinated biphenyl (PCB) concentration found was 11.1 μg/g in eggs from Akwesasne Reserve, New York, USA, on the St. Lawrence River, whereas the highest p, p′‐DDE concentration of 2.57 μg/g was found in eggs from Mud Creek, Ontario, Canada, in the Lake Erie watershed. Concentrations of other organochlorine pesticides and chlorobenzenes were low and not variable among sites. Significant differences in hepatic EROD activity, retinol and retinyl palmitate, and uroporphyrin in nestling birds existed among sites. Ethoxyresorufin O‐deethylase activity was highest and retinol and retinyl palmitate were lowest at Cornwall Island, Ontario, Canada, in the St. Lawrence River, whereas porphyrins were highest at Toronto and Hamilton harbors, Ontario, Canada, in Lake Ontario. Ethoxyresorufin O‐deethylase induction was significantly and negatively correlated with nestling hepatic retinol concentrations, whereas uroporphyrin concentrations were positively correlated with PCB congener 118 in nestlings. In contrast, few differences occurred in vitamin A concentrations in diet samples among sites. Together, these findings suggest that depressed hepatic vitamin A and elevated highly carboxylated porphyrin concentrations are strongly associated with sites with the highest organochlorine exposure in tree swallows.

Abstract-Reproduction and biochemical indicators (vitamin A, ethoxyresorufin-O-deethylase [EROD], highly carboxylated porphyrins) of contaminant effects, and concentrations of organochlorine residues were measured in tree swallows from wetlands within the watersheds of the Great Lakes and the St. Lawrence River, USA and Canada. To assess the vitamin A sources in the tree swallow diets, insects were collected, by ligature, from nestlings at four of these sites. Diet samples were analyzed for retinol and ␣-and ␤-carotene. Marked differences were found in chlorinated hydrocarbon residues in eggs and nestlings among sites; however, we did not find any significant differences in hatching or fledging success. The maximum polychlorinated biphenyl (PCB) concentration found was 11.1 g/g in eggs from Akwesasne Reserve, New York, USA, on the St. Lawrence River, whereas the highest p,pЈ-DDE concentration of 2.57 g/g was found in eggs from Mud Creek, Ontario, Canada, in the Lake Erie watershed. Concentrations of other organochlorine pesticides and chlorobenzenes were low and not variable among sites. Significant differences in hepatic EROD activity, retinol and retinyl palmitate, and uroporphyrin in nestling birds existed among sites. Ethoxyresorufin Odeethylase activity was highest and retinol and retinyl palmitate were lowest at Cornwall Island, Ontario, Canada, in the St. Lawrence River, whereas porphyrins were highest at Toronto and Hamilton harbors, Ontario, Canada, in Lake Ontario. Ethoxyresorufin Odeethylase induction was significantly and negatively correlated with nestling hepatic retinol concentrations, whereas uroporphyrin concentrations were positively correlated with PCB congener 118 in nestlings. In contrast, few differences occurred in vitamin A concentrations in diet samples among sites. Together, these findings suggest that depressed hepatic vitamin A and elevated highly carboxylated porphyrin concentrations are strongly associated with sites with the highest organochlorine exposure in tree swallows.

We examined the breeding success of two insectivorous bird species, the resident black-capped chickadee (Parus atricapillus) and the Neotropical migrant chestnut-sided warbler (Dendroica pensylvanica), in relation to food-chain chemistry at a healthy and a declining forest site in central Ontario, Canada. The health of sugar maples (Acer saccharum) was poorer and the pH of both soil and throughfall was lower at the declining site than at the healthy site. The calcium and magnesium concentrations and the ca1cium:aluminum ratio in the soil were also lower at the declining site than at the healthy site. The calcium, magnesium, and phosphorus concentrations and the ca1cium:aluminum ratio in sugar maple foliage were lower at the declining site than at the healthy site, indicating extensive acid leaching of the soil and foliage at the declining site. Caterpillars (Geometridae) at the declining site had a lower calcium concentration and beetles had a lower magnesium concentration than these groups at the healthy site. The ca1cium:aluminum ratios in the tissues of insects in both groups were lower at the declining site than at the healthy site, paralleling the foliar and soil chemical differences. There were, however, no differences in clutch or brood sizes, or percent hatch, for either bird species between the healthy and declining sites. Chickadees consistently foraged lower in the canopy at the declining site, a possible compensatory behaviourial response to canopy dieback and (or) lower food quality in the upper canopy.RCsumC : Nous avons CtudiC le succks de la reproduction chez deux espkces d'oiseaux insectivores, la MCsange 8 tCte noire (Parus atricapillus), une espkce rCsidante, et la Paruline h flancs marrons (Dendroica pensylvanica), une espkce migratrice NCotropicale, en rapport avec la chimie de la chaine alimentaire dans des habitats forestiers sains et en dCclin du centre de I'Ontario, Canada. Dans la forCt en dCclin, la santC des Crables 8 sucre (Acer saccharum) Ctait moins bonne et le pH du sol et des pluies non intercepties Ctait plus faible que dans la forCt saine. Dans le sol de la forCt en dCclin, les concentrations de calcium, de magnCsium et le rapport calcium : aluminium Ctaient plus faibles qu'au site sain. Les concentrations de calcium, de magnCsium, de phosphore et de rapport calcium : aluminium dans le feuillage des Crables 8 sucre Ctaient Cgalement plus faibles que dans la forCt saine, ce qui indique un important lessivage 8 l'acide du sol et du feuillage dans la forCt en dCclin. Les chenilles des Geometridae contenaient moins de calcium et les colCoptkres, moins de magnksium, au site affect6 qu'au site sain. Les rapports calcium : aluminium dans les tissus des insectes des deux groupes Ctaient plus faibles au site affect6 que dans la for& saine, suivant les mCmes tendances que les diffkrences chimiques dans le feuillage et dans le sol. Par ailleurs, il n'y avait pas de diffkrence dans le nombre d'oeufs, le nombre d'oisillons ou le nombre d'oisillons parvenus 8 1'Cclosion entre les deux sites. ...

Green. 2010. Vesper sparrows and western meadowlarks show a mixed response to cattle grazing in the intermountain region of British Columbia. Avian Conservation and Ecology -Écologie et conservation des oiseaux 5(1): ABSTRACT. Livestock grazing in the shortgrass steppe of the Intermountain region of British Columbia is predicted to have significant effects on grassland habitats and their associated ground-nesting bird communities. We tested whether grazed and ungrazed sites could be discriminated on the basis of their vegetation communities, whether the abundance of two ground-nesting bird species, Vesper Sparrow (Pooecetes gramineus) and Western Meadowlark (Sturnella neglecta), differed between grazed and ungrazed sites, and whether vegetation variables found to differ between grazed and ungrazed plots could be used to predict the abundance of the two bird species at a fine scale. Grazed sites were easily distinguishable from a site that had been ungrazed for >30 years based on the structure and composition of their vegetation communities. However, more detailed grazing categories could not be distinguished on the basis of vegetation characteristics. Despite the existence of grazing effects on vegetation structure and composition, we found no consistent differences in abundance of Vesper Sparrows and Western Meadowlarks between the grazed and ungrazed sites. However, there was weak evidence that the abundance of both species was higher at fine-scale plots (100 m radius point count station) with less bare ground and taller vegetation. Bare ground cover was lower on grazed plots, but vegetation was taller on ungrazed plots. Combined, our results suggest that low intensity grazing leads to grassland habitat change with both negative and positive effects on Vesper Sparrows and Western Meadowlarks, resulting in no net change in their broad-scale abundance.RÉSUMÉ. On pense que le broutement du bétail dans la steppe de la région intramontagnarde de la Colombie-Britannique a des effets significatifs sur les milieux de prairie et les communautés d'oiseaux nichant au sol qui y sont associées. Nous avons testé les hypothèses suivantes : 1) Est-il possible de discriminer les sites broutés des sites non broutés à partir de leur communauté végétale? 2) L'abondance de deux espèces d'oiseaux nichant au sol, le Bruant vespéral (Pooecetes gramineus) et la Sturnelle de l'Ouest (Sturnella neglecta), diffère-t-elle selon le type de sites (broutés vs non broutés)? 3) Les variables relatives à la végétation qui diffèrent entre les sites broutés et les sites non broutés peuvent-elles servir à prévoir l'abondance des deux espèces d'oiseaux à une échelle fine? Les sites broutés ont été faciles à distinguer des sites qui n'avaient pas été broutés depuis plus de 30 ans, d'après la structure et la composition de leur communauté végétale. Toutefois, des catégories de broutement plus détaillées n'ont pas pu être déterminées à partir des caractéristiques végétales. Bien que le broutement ait des effets sur la structure et la composition végé...