Although poisoning from anthropogenically derived lead threatens wildlife of many species, routes of lead exposure are unclear and rarely empirically tested. We used blood lead concentration and isotope ratio ( 207 Pb/ 206 Pb) data from populations of four species of raptors from across North America to test hypotheses associated with lead exposure via inhalation versus ingestion. Mean variation in blood lead concentration among cohort siblings was non-zero at nests of ferruginous hawks Buteo regalis and osprey Pandion haliaetus (P < 0.001 and P < 0.001), indicating exposure via episodic ingestion. However, within-nest variation in blood lead concentration was not significantly different from zero among cohort siblings at nests of bald eagles Haliaeetus leucocephalus and golden eagles Aquila chrysaetos (P = 0.014 and P = 0.023), consistent with exposure via continuous inhalation. Isotope ratio data corroborated the lead concentration data and within-nest average and variance of blood lead concentrations were positively correlated (r = 0.70 to 0.94), indicating episodic ingestion. This study provides some of the first empirical population-level data to evaluate mechanisms of lead exposure and demonstrates the importance of lead ingestion to avian predators and scavengers.

ABSTRACT. The Short-eared Owl (Asio flammeus) is an open-country species breeding in the northern United States and Canada, and has likely experienced a long-term, range-wide, and substantial decline. However, the cause and magnitude of the decline is not well understood. We set forth to address the first two of six previously proposed conservation priorities to be addressed for this species:(1) better define habitat use and (2) improve population monitoring. We recruited 131 volunteers to survey over 6.2 million ha within the state of Idaho for Short-eared Owls during the 2015 breeding season. We surveyed 75 transects, 71 of which were surveyed twice, and detected Short-eared Owls on 27 transects. We performed multiscale occupancy modeling to identify habitat associations, and performed multiscale abundance modeling to generate a state-wide population estimate. Our results suggest that within the state of Idaho, Short-eared Owls are more often found in areas with marshland or riparian habitat or areas with greater amounts of sagebrush habitat at the 1750 ha transect scale. At the 50 ha point scale, Short-eared Owls tend to associate positively with fallow and bare dirt agricultural land and negatively with grassland. Cropland was not chosen at the broader transect scale suggesting that Short-eared Owls may prefer more heterogeneous landscapes. On the surface our results may seem contradictory to the presumed land use by a "grassland" species; however, the grasslands of the Intermountain West, consisting largely of invasive cheatgrass (Bromus tectorum), lack the complex structure shown to be preferred by these owls. We suggest the local adaptation to agriculture represents the next best habitat to their historical native habitat preferences. Regardless, we have confirmed regional differences that should be considered in conservation planning for this species. Last, our results demonstrate the feasibility, efficiency, and effectiveness of utilizing public participation in scientific research to achieve a robust sampling methodology across the broad geography of the Intermountain West.Recensement de Hiboux des marais (Asio flammeus) dans la région Intramontagnarde Ouest nordaméricaine : utilisation de la participation citoyenne pour effectuer un suivi à grande échelle RÉSUMÉ. Le Hibou des marais (Asio flammeus), espèce de milieux ouverts nichant dans le nord des États-Unis et au Canada, a vraisemblablement subi une baisse importante de longue date et à grande échelle. Toutefois, la cause et la magnitude de cette baisse ne sont pas bien comprises. Nous avons choisi d'étudier les deux premières de six priorités de conservation proposées antérieurement pour cette espèce : 1) mieux établir l'utilisation de l'habitat; et 2) améliorer le suivi de la population. Nous avons recruté 131 bénévoles pour inventorier plus de 6,2 millions d'ha dans l'État de l'Idaho durant la saison de nidification 2015 du Hibou des marais. Nous avons inventorié 75 transects, dont 71 à deux reprises, et avons détecté le Hibou des marais dans 27...

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Timing of activity can reveal an organism's efforts to optimize foraging either by minimizing energy loss through passive movement or by maximizing energetic gain through foraging. Here, we assess whether signals of either of these strategies are detectable in the timing of activity of daily, local movements by birds. We compare the similarities of timing of movement activity among species using six temporal variables: start of activity relative to sunrise, end of activity relative to sunset, relative speed at midday, number of movement bouts, bout duration and proportion of active daytime hours. We test for the influence of flight mode and foraging habitat on the timing of movement activity across avian guilds. We used 64 570 days of GPS movement data collected between 2002 and 2019 for local (non-migratory) movements of 991 birds from 49 species, representing 14 orders. Dissimilarity among daily activity patterns was best explained by flight mode. Terrestrial soaring birds began activity later and stopped activity earlier than pelagic soaring or flapping birds. Broad-scale foraging habitat explained less of the clustering patterns because of divergent timing of active periods of pelagic surface and diving foragers. Among pelagic birds, surface foragers were active throughout all 24 hrs of the day while diving foragers matched their active hours more closely to daylight hours. Pelagic surface foragers also had the greatest daily foraging distances, which was consistent with their daytime activity patterns. This study demonstrates that flight mode and foraging habitat influence temporal patterns of daily movement activity of birds.

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