Local and regional-scale effects of hedgerows on grassland- and forest-associated bird populations within agroecosystems.

Linear woody features (LWFs), like hedgerows along field edges, provide wildlife habitat and support biodiversity in agroecosystems. Assessments of LWFs usually focus on community-level indices, such as species richness. However, effective conservation actions need to balance the contrasting habitat preferences of different wildlife species, necessitating a focus on population-level effects in working landscapes. We assessed associations between LWFs and abundance for 45 bird species within an intensive agroecosystem in eastern Ontario, Canada. We used distance- and removal-sampling methods across 4 years (2016-2019) to estimate local bird abundance in habitats representing a range of LWF densities. We also predicted abundance across a subset of the study region with and without LWFs to understand their contribution to regional population density. Associations between local bird abundance and LWFs were variable among species, but overall community effects were clearly positive, particularly for forest and shrubland species. At the site level, 20/45 species (44%) had higher densities associated with greater LWF presence on average, compared to 5/45 (11%) with negative associations. At the regional scale, LWFs had predicted benefits on total abundance for 31 species (69%), contributing to an estimated 20% increase on average. Positive effects were most pronounced in areas with greater agricultural land use (primarily field crops), suggesting LWFs may provide crucial habitat in heavily modified landscapes but have little to no additional benefit for the avian community in areas with greater existing heterogeneity and habitat retention. Species that responded negatively tended to be at risk with strong habitat preferences for intact forests or large, open grasslands and, thus, greater sensitivity to potential edge effects. With rapidly declining songbird populations and a global need for food security, conservation strategies that amplify biodiversity and enhance agricultural productivity through ecosystem services such as pest control, pollination, and water regulation are vital. We demonstrate the benefits of habitat heterogeneity in agroecosystems on songbird densities and highlight the need to integrate local and landscape-level assessments in conservation planning. An effective, balanced strategy includes concentrating LWFs in areas of extensive arable crops, with habitat retention patches where possible, while maintaining heterogeneity through mixtures of natural habitats and pastoral farming in less intensive regions.

Les caractéristiques d'emboisement linéaires (CEL), tels que les haies en bordure de champs, fournissent un habitat à la faune et à la flore et favorisent la biodiversité dans les agroécosystèmes. Les évaluations des caractéristiques d'emboisement linéaires se concentrent généralement sur des indices au niveau de la communauté, tels que la richesse des espèces. Cependant, pour être efficaces, les actions de conservation doivent équilibrer les préférences variables des différentes espèces sauvages en matière d'habitat, ce qui nécessite de se concentrer sur les effets au niveau de la population dans les paysages exploités. Nous avons évalué les associations entre les CEL et l'abondance de 45 espèces d'oiseaux dans un agroécosystème intensif de l'est de l'Ontario, au Canada. Nous avons utilisé des méthodes d'échantillonnage par distance et par enlèvement sur quatre ans (2016­2019) pour estimer l'abondance locale des oiseaux dans des habitats représentant une gamme de densités de CEL. Nous avons également prédit l'abondance dans un sous­ensemble de la région étudiée avec et sans CEL pour comprendre leur contribution à la densité de la population régionale. Les associations entre l'abondance des oiseaux locaux et les CEL étaient variables d'une espèce à l'autre, mais les effets globaux sur les communautés étaient clairement positifs, en particulier pour les espèces des forêts et des zones arbustives. Au niveau du site, 20/45 espèces (44%) avaient des densités plus élevées associées à une plus grande présence de CEL en moyenne, contre 5/45 (11%) avec des associations négatives. À l'échelle régionale, les CEL ont eu des effets bénéfiques sur l'abondance totale de 31 espèces (69%), contribuant à une augmentation estimée à 20% en moyenne. Les effets positifs étaient plus prononcés dans les zones où l'utilisation des terres agricoles était plus importante (principalement les grandes cultures), ce qui suggère que les CEL peuvent fournir un habitat crucial dans les paysages fortement modifiés, mais qu'elles ont peu ou pas d'avantages supplémentaires pour la communauté aviaire dans les zones où l'hétérogénéité existante et la conservation de l'habitat sont plus importantes. Les espèces qui ont répondu négativement avaient tendance à être en danger, avec de fortes préférences d'habitat pour les forêts intactes ou les grandes prairies ouvertes, et donc une plus grande sensibilité aux effets de lisière potentiels. Avec le déclin rapide des populations d'oiseaux chanteurs et le besoin mondial de sécurité alimentaire, les stratégies de conservation qui amplifient la biodiversité et améliorent la productivité agricole grâce aux services écosystémiques tels que la lutte contre les ravageurs, la pollinisation et la régulation de l'eau sont vitales. Nous démontrons les avantages de l'hétérogénéité de l'habitat dans les agroécosystèmes sur les densités de passereaux et soulignons la nécessité d'intégrer les évaluations locales et au niveau du paysage dans la planification de la conservation. Une stratégie efficace et équilibrée consiste à concentrer les CEL dans les zones de cultures arables extensives, avec des parcelles de conservation de l'habitat là où c'est possible, tout en maintenant l'hétérogénéité grâce à des mélanges d'habitats naturels et à l'agriculture pastorale dans les régions moins intensives.

Organochlorine contaminants in seven species of Arctic seabirds from northern Baffin Bay.

Organochlorine contaminants (OCs) were determined in liver and fat of seven species of seabirds (Alle alle, Uria lomvia, Cepphus grylle, Rissa tridactyla, Pagophila eburnea, Larus hyperboreus, and Fulmaris glacialis) collected in May/June 1998 from the Northwater Polynya in northern Baffin Bay. OC concentrations ranged over an order of magnitude between seabird species and OC groups, with PCBs having the highest concentrations followed by DDT, chlordane, HCH and ClBz. Positive relationships between delta15N (estimator of trophic level) and OC concentrations (lipid basis) were found for all OC groups, showing that trophic position and biomagnification significantly influence OC concentrations in Arctic seabirds. Concentrations of a number of OCs in particular species (e.g., HCH in P. eburnean) were lower than expected based on delta15N and was attributed to biotransformation. P. eburnea and F. glacialis, which scavenge, and R. tridactyla, which migrate from the south, were consistently above the delta15N-OC regression providing evidence that these variables can elevate OC concentrations. Stable isotope measurements in muscle may not be suitable for identifying past scavenging events by seabirds. OC relative proportions were related to trophic position and phylogeny, showing that OC biotransformation varies between seabird groups. Trophic level, migration, scavenging and biotransformation all play important roles in the OCs found in Arctic seabirds.

Reproductive and morphological effects of halogenated dimethyl bipyrroles on captive American kestrels (Falco sparverius).

Sixty-four adult captive American kestrels (Falco sparverius) were exposed to a dietary source of halogenated dimethyl bipyrroles (HDBPs), a group of organohalogens proposed to have a natural origin. Adult kestrels were assigned to four treatment groups that were administered a different dose of HDBPs [high, 140 microg/(bird x d); medium, 4.3 microg/(bird x d); low, 0.13 microg/(bird x d); control, 0 microg/(bird x d)]. Exposure began prior to pairing and continued during breeding until approximately 28 d after hatching of the final eggs. Juvenile and adult kestrels accumulated HDBPs in carcass tissue, plasma, and liver. In addition, HDBPs were transferred to yolks during egg development. Low dietary absorption efficiencies (0.011-0.029) indicated that HDBPs were effectively cleared from kestrels either from increased elimination, metabolism, or a combination of the two processes. Reproductive and morphological endpoints examined for HDBP-induced changes included egg volume, egg mass, eggshell thickness, egg fertility, clutch size, liver and whole body mass, antebrachium, central retrice, tarsus, ninth primary, and wing cord lengths. Few statistically significant dose-dependent effects were observed. Hepatic tissue samples from selected individuals underwent histomorphological evaluation. Although the hepatic function was not evaluated specifically in these birds, no clinical signs suggestive of liver disease or gross hepatic anomalies were observed. Only minor histomorphological changes were detected in the hepatic tissue. The lack of serious effects suggests that HDBPs are not an acute reproductive threat to avian populations.

Pentachlorophenol and hydroxylated polychlorinated biphenyl metabolites in umbilical cord plasma of neonates from coastal populations in Québec.

Concentrations of polychlorinated biphenyls (PCBs), hydroxylated metabolites of PCBs (HO-PCBs) and octachlorostyrene (4-HO-HpCS), and pentachlorophenol (PCP) were determined in umbilical cord plasma samples from three different regions of Québec. The regions studied included two coastal areas where exposure to PCBs is high because of marine-food-based diets--Nunavik (Inuit people) and the Lower North Shore of the Gulf of St. Lawrence (subsistence fishermen)--and a southern Québec urban center where PCB exposure is at background levels (Québec City). The main chlorinated phenolic compound in all regions was PCP. Concentrations of PCP were not significantly different among regions (geometric mean concentration 1,670 pg/g, range 628-7,680 pg/g wet weight in plasma). The ratio of PCP to polychlorinated biphenyl congener number 153 (CB153) concentration ranged from 0.72 to 42.3. Sum HO-PCB (sigma HO-PCBs) concentrations were different among regions, with geometric mean concentrations of 553 (range 238-1,750), 286 (103-788), and 234 (147-464) pg/g wet weight plasma for the Lower North Shore, Nunavik, and the southern Québec groups, respectively. Lower North Shore samples also had the highest geometric mean concentration of sum PCBs (sum of 49 congeners; sigma PCBs), 2,710 (525-7,720) pg/g wet weight plasma. sigma PCB concentrations for Nunavik samples and southern samples were 1,510 (309-6,230) and 843 (290-1,650) pg/g wet weight plasma. Concentrations (log transformed) of sigma HO-PCBs and sigma PCBs were significantly correlated (r = 0.62, p < 0.001), as were concentrations of all major individual HO-PCB congeners and individual PCB congeners. In Nunavik and Lower North Shore samples, free thyroxine (T4) concentrations (log transformed) were negatively correlated with the sum of quantitated chlorinated phenolic compounds (sum PCP and sigma HO-PCBs; r = -0.47, p = 0.01, n = 20) and were not correlated with any PCB congeners or sigma PCBs. This suggests that PCP and HO-PCBs are possibly altering thyroid hormone status in newborns, which could lead to neurodevelopmental effects in infants. Further studies are needed to examine the effects of chlorinated phenolic compounds on thyroid hormone status in newborns.