ABSTRACT. Swallows, along with other aerial insectivores, are experiencing steep population declines. Decreased insect abundance has been implicated as a potential cause of the decline. However, to determine if there is a guild-level effect of reduced insect abundance on swallows, research is needed to examine relationships between insect abundance and breeding success for multiple species. The goal of our study was two-fold. First, we determined if insect abundance during nestling rearing varied with breeding phenology for three species of swallows, Barn (Hirundo rustica), Cliff (Petrochelidon pyrrhonota), and Tree Swallows (Tachycineta bicolor), such that swallows breeding when insects are abundant have greater success. Then we determined if insect abundance was related to nestling survival and mass (as a proxy for postfledgling survival). We collected insects daily at each of three study sites during the breeding season, monitored swallow nests to determine breeding phenology and success, and weighed nestlings at or just prior to the peak of rapid nestling growth to determine mass. We found early hatching Cliff and Tree Swallow nests had higher insect abundance during nestling rearing. However, neither nestling survival nor mass were related to insect abundance. Our results suggest that breeding success in three species of swallows was not related to insect abundance in our study area. We suggest that the role of insect abundance on aerial insectivore declines may vary across their geographic range, and call for broad-scale, multispecies research on aerial insectivore declines. Absence d'effet du nombre d'insectes sur la survie et le poids des oisillons de trois insectivores aériensRÉSUMÉ. Les populations d'hirondelles, tout comme celles d'autres insectivores aériens, affichent des baisses marquées. Pour expliquer celles-ci, la diminution du nombre d'insectes a été soulevée comme cause possible. Toutefois, des études examinant la relation entre la quantité d'insectes et le succès de reproduction de plusieurs espèces sont nécessaires afin de déterminer si la quantité réduite d'insectes a un effet sur l'ensemble des espèces d'hirondelles. La présente étude avait deux objectifs. Le premier était de déterminer si la quantité d'insectes durant l'élevage des oisillons variait en fonction de la phénologie de nidification de trois espèces d'hirondelles, l'Hirondelle rustique (Hirundo rustica), l'Hirondelle à front blanc (Petrochelidon pyrrhonota) et l'Hirondelle bicolore (Tachycineta bicolor), de sorte que les hirondelles qui nichent au moment où les insectes sont nombreux devraient avoir un meilleur succès que celles qui ne le font pas. Le second objectif était de déterminer si la quantité d'insectes était reliée à la survie et au poids des oisillons (comme indicateur de la survie des jeunes ayant pris leur envol). Nous avons récolté quotidiennement des insectes à chacun des trois sites d'étude durant la saison de nidification, suivi des nids d'hirondelles afin de déterminer la phénologie et le succès de nidificatio...

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Swallow (Family: Hirundinidae) populations in the Canadian Maritimes have declined since the 1980s. Using mark-recapture data from 2012–2019, we determined apparent annual adult survival rates for Barn Hirundo rustica Linnaeus, 1758, Tree Tachycineta bicolor Vieillot, 1808, Bank Riparia riparia Linnaeus, 1758, and Cliff swallows Petrochelidon pyrrhonota Vieillot, 1817. For two data-rich species (Barn and Tree swallows), we modelled the relationships between survival and weather (cold snaps, precipitation, temperature, and wind speed); climate (El Niño-Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO)); Enhanced Vegetation Index (EVI) as a measure of primary productivity during the winter; number of active nests as a measure of site quality; and the Breeding Bird Survey (BBS) annual population index as density dependent processes. Survival rates for all four species were typically higher (Barn and Tree) or similar to (Cliff and Bank) of estimates from populations that have not undergone severe, long-term declines. Across weather and climate variables, conditions that are typically favourable for high insect availability (e.g., higher precipitation, warmer temperatures and lower wind speeds) resulted in higher survival. For female Barn and Tree Swallows, survival was higher when EVI was lower, and for Barn Swallows, survival was also higher when the BBS index was higher. Collectively our results demonstrate that conditions throughout the annual cycle affect survival, and the relationships with weather and climate variables support the importance of high insect availability