ABSTRACT. Carcass removal by scavengers has been identified as one of the largest biases in estimating bird mortality from anthropogenic sources. Only two studies have examined carcass removal by scavengers in an urban environment, and previous estimates of bird-window collision mortality at houses have relied on carcass removal rates from wind turbine studies. We placed a bird carcass and time-lapse camera at 44 houses in Edmonton, Alberta. In total, 166 7-day trials were conducted throughout 2015. Time-to-event (survival) analysis was used to identify covariates that affected removal. The carcass removal rate was determined for use in estimating the number of birds killed from bird-window collisions at houses in Alberta. In total, 67.5% of carcasses were removed. The date the carcass was placed, the year the house was built, and the level of development within 50 m of the house were the covariates that had the largest effect on carcass removal. In calculating our removal rate, the number of detected carcasses in the first 24 hours was adjusted by 1.47 to account for removal by scavengers. Previously collected citizen science data were used to create an estimate of 957,440 bird deaths each year in Alberta as a result of bird-window collisions with houses. This number is based on the most detailed bird-window collision study at houses to date and a carcass removal study conducted in the same area. Similar localized studies across Canada will need to be completed to reduce the biases that exist with the previous bird-window collision mortality estimate for houses in Canada. Incorporation du prélèvement de carcasses d'oiseaux par les charognards urbains dans l'estimation du taux de collision des oiseaux avec les fenêtresRÉSUMÉ. Le prélèvement de carcasses par les charognards a été identifié comme un des biais les plus importants dans l'estimation de la mortalité d'oiseaux attribuable à des causes d'origine humaine. Seules deux études ont examiné le prélèvement de carcasses par les charognards en milieu urbain, et les estimations précédentes de la mortalité d'oiseaux par collision avec les fenêtres de maisons ont utilisé des taux de prélèvement de carcasses provenant d'études réalisées pour les éoliennes. Nous avons déposé des carcasses d'oiseaux et positionné des caméras à prises de vues par intervalle à 44 maisons à Edmonton, Alberta. En tout, 166 essais de 7 jours ont été effectués en 2015. Une analyse du temps d'apparition de l'événement (survie) a été faite pour déterminer les covariables qui agissent dans le prélèvement de carcasses. Le taux de prélèvement de carcasses a été établi afin d'être subséquemment utilisé dans l'estimation du nombre d'oiseaux morts par collision avec les fenêtres de maisons en Alberta. Nous avons estimé ce taux à 67,5 %. La date de dépôt de la carcasse, l'année de construction de la maison et le degré d'urbanisation dans un rayon de 50 m de la maison étaient les covariables qui avaient le plus d'effets sur le prélèvement de carcasses. Dans notre calcul du taux de prélèvement, le nom...

Understanding bird migration and dispersal is important to inform full life-cycle conservation planning. Stable hydrogen isotope ratios from feathers (δ2Hf) can be linked to amount-weighted long-term, growing season precipitation δ2H (δ2Hp) surfaces to create δ2Hf isoscapes for assignment to molt origin. However, transfer functions linking δ2Hp with δ2Hf are influenced by physiological and environmental processes. A better understanding of the causes and consequences of variation in δ2Hf values among individuals and species will improve the predictive ability of geographic assignment tests. We tested for effects of species, land cover, forage substrate, nest substrate, diet composition, body mass, sex, and phylogenetic relatedness on δ2Hf from individuals at least two years old of 21 songbird species captured during the same breeding season at a site in northeastern Alberta, Canada. For four species, we also tested for a year × species interaction effect on δ2Hf. A model including species as single predictor received the most support (AIC weight = 0.74) in explaining variation in δ2Hf. A species-specific variance parameter was part of all best-ranked models, suggesting variation in δ2Hf was not consistent among species. The second best-ranked model included a forage substrate × diet interaction term (AIC weight = 0.16). There was a significant year × species interaction effect on δ2Hf suggesting that interspecific differences in δ2Hf can differ among years. Our results suggest that within- and among-year interspecific variation in δ2Hf is the most important source of variance typically not being explicitly quantified in geographic assignment tests using non-specific transfer functions to convert δ2Hp into δ2Hf. However, this source of variation is consistent with the range of variation from the transfer functions most commonly being propagated in assignment tests of geographic origins for passerines breeding in North America.

Heavy and frequent rain, low temperatures, and strong winds may decrease adult foraging time, cause thermoregulatory stress on nestlings, and lead to nest damage or destruction, all of which can negatively affect breeding success. However, certain parental behaviours can mitigate these potentially negative effects of inclement weather. We examined how parents could mitigate these negative weather effects by adjusting three behavioursnest attendance, prey deliveries, and nest maintenancebefore, during, and after storms at 11 nests of the at-risk Ferruginous Hawk (Buteo regalis) in Canada. Female adults spent an increasing amount of time on the nest as wind speed increased. Similar numbers of prey were delivered before and after storms, suggesting that Ferruginous Hawks do not compensate for lost foraging time. They appeared to demonstrate an ability to detect approaching storms, possibly by responding to falling barometric pressure cues, and may have mitigated the risk of nest damage by increasing their nest maintenance behaviours. Our study is among the first to observe storm preparation behaviour, and indicates that some raptorial birds have the ability to alter nesting behaviour in response to approaching inclement weather. Zusammenfassung Königsbussarde (Buteo regalis) verändern das elterliche Verhalten bei heraufziehenden Stü rmenStarke und andauernde Regenfälle, niedrige Temperaturen und starke Winde können die Zeit der Nahrungssuche von Adulten verringern. Dies verursacht thermoregulatorischen Stress bei den Nestlingen und kann zu Schaden oder Vernichtung der Brut führen, was insgesamt den Bruterfolg negativ beeinflussen kann. Dennoch können bestimmte elterliche Verhaltensweisen diese potentiell negativen Schlecht-Wetter-Effekte abmildern. Wir untersuchten, wie Eltern diese negativen Wettereinflüsse durch die Anpassung von drei Verhaltensweisen abschwächen konnten: Anwesenheit am Nest, Beuteübergaben und Brutpflege vor, während und nach Stürmen an 11 Nestern des gefährdeten Königsbussard (Buteo regalis) in Kanada. Adulte Weibchen verbrachten mehr Zeit auf dem Nest mit zunehmender Windgeschwindigkeit und stärker werdenden Regenfällen. Vor und nach den Stürmen wurden ähnliche Anzahlen an Beuteobjekten eingetragen, was darauf hindeutet, dass Königsbussarde verlorene Zeiten zur Nahrungssuche nicht kompensieren. Königsbussarde scheinen die Fähigkeit zu haben, heraufziehende Stürme zu erkennen, in dem sie auf fallenden Luftdruck reagieren und das Risiko eines Brutverlustes durch zunehmende Brutpflege minimieren. Unsere Studie gehört zu den ersten, die sturmvorbereitendes Verhalten beobachten konnte und zeigt, dass Greifvögel in der Lage sind, ihr Brutverhalten als Antwort auf raue Witterungsbedingungen anzupassen.

The expansion of humans and their related infrastructure is increasing the likelihood that wildlife will interact with humans. When disturbed by humans, animals often change their behaviour, which can result in time and energetic costs to that animal. An animal's decision to change behaviour is likely related to the type of disturbance, the individual's past experience with disturbance, and the landscape in which the disturbance occurs. In southern Alberta and Saskatchewan, we quantified probability of flight initiation from the nest by Ferruginous Hawks (Buteo regalis) during approaches to nests by investigators. We tested if probability of flight was related to different disturbance types, previous experience, and the anthropogenic landscape in which individual Ferruginous Hawks nested. Probability of flight was related to the type of approach by the investigator, the number of previous visits by investigators, and the vehicular traffic around the nest. Approaches by humans on foot resulted in a greater probability of flight than those in a vehicle. Approaches in a vehicle via low traffic volume access roads were related to increased probability of flight relative to other road types. The number of previous investigator approaches to the nest increased the probability of flight. Overall, we found support that Ferruginous Hawks show habituation to vehicles and the positive reinforcement hypotheses as probability of flight was negatively related to an index of traffic activity near the nest. Our work emphasizes that complex, dynamic processes drive the decision to initiate flight from the nest, and contributes to the growing body of work explaining how responses to humans vary within species.

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