The classical theory of island biogeography , which predicts species richness using island area and isolation, has been expanded to include contributions from marine subsidies, i.e. subsidized island biogeography (SIB) theory . We tested the effects of marine subsidies on species diversity and population density on productive temperate islands, evaluating SIB predictions previously untested at comparable scales and subsidy levels. We found that the diversity of terrestrial breeding bird communities on 91 small islands (approx. 0.0001–3 km 2 ) along the Central Coast of British Columbia, Canada were correlated most strongly with island area, but also with marine subsidies. Species richness increased and population density decreased with island area, but isolation had no measurable influence. Species richness was negatively correlated with marine subsidy, measured as forest-edge soil δ 15 N. Density, however, was higher on islands with higher marine subsidy, and a negative interaction between area and subsidy indicates that this effect is stronger on smaller islands, offering some support for SIB. Our study emphasizes how subsidies from the sea can shape diversity patterns on islands and can even exceed the importance of isolation in determining species richness and densities of terrestrial biota.

Although marine subsidies often enrich terrestrial ecosystems, their influence is known to be context‐dependent. Additionally, the multitrophic impact of marine subsidies has not been traced through food webs across physically diverse islands. Here, we test predictions about how island characteristics can affect marine enrichment of food web constituents and how nutrients flow through island food webs. To evaluate enrichment and trace marine nutrients across food webs, we used stable isotopes of soil, flora, and fauna (n = 4752 samples) collected from 97 islands in British Columbia, Canada. Island area was the strongest predictor of enrichment across taxa; we found that samples were more 15N‐rich on smaller islands. Enrichment declined with distance from shore but less so on small islands, implying a higher per‐unit‐area subsidy effect. These area and distance‐to‐shore effects were taxon‐specific, and nearly twice as strong in basal food web groups. We also found that increases in δ15N correlated with increases in %N in basal trophic groups, as well as in songbirds, implying biologically relevant uptake of a potentially limiting nutrient. Path analysis demonstrated that subsidies in soil flow through plants and detritivores, and into upper‐level consumers. Our results reveal an interplay between island biogeography and marine subsidies in shaping island food webs through bottom‐up processes.

Background To effectively conserve migratory species, the entire range encompassed by their annual life cycle needs to be considered. Most research on Nearctic-Neotropical migratory birds has focused on the breeding grounds resulting in a general lack of knowledge regarding the wintering and migratory periods. The Canada Warbler (Cardellina canadensis) has declined by 71% from 1970 to 2012, at a rate of 2.9% per year, and is listed as Threatened in Canada. As with most Nearctic-Neotropical migrants, conservation efforts outside the breeding range are limited by a poor understanding of migration routes and the connectivity between specific breeding and wintering populations. Results To determine migratory routes of multiple breeding populations of Canada Warblers, we directly-tracked individuals using light-level geolocators deployed at four sites across the breeding range, spanning approximately 43 degrees in longitude (Alberta, Manitoba and Québec, Canada, and New Hampshire, USA). Twenty-five geolocators with usable data were recovered from three sites and were analyzed using FlightR to determine fall migration routes (n = 18) and individual wintering sites (n = 25). Individuals from all breeding populations took a western fall migration route at the Gulf of Mexico; with 77.8% of birds funnelling into a narrow geographic space along the western side of the Gulf of Mexico (97°W-99°W). We found no evidence for population-specific, parallel migration routes. Most individuals (72%) overwintered in Colombia. The remaining individuals overwintered in Venezuela. Conclusions Our results demonstrate convergence of migratory routes around a migration barrier for individuals originating from widely distributed breeding areas. Further, we suggest the potential importance of habitat around the Gulf of Mexico during migration and Andean forest in Colombia as overwintering habitat for this threatened species. Future research should be directed at understanding how these areas are used by Canada Warblers.

Understanding spatial and temporal movement patterns of migratory birds throughout the annual cycle can help identify potential population threats. The behavior and habitat use of birds during migration and stopover periods is particularly understudied in many species. In this study, we used high spatial resolution archival GPS tags to track Rusty Blackbirds (Euphagus carolinus) from one eastern (New Hampshire) and two western (Alaska and Alberta) breeding populations across the annual cycle. We sought to determine: 1) migratory connectivity of the three distinct populations; 2) migratory phenology, behavior, and time spent during each phase of the annual cycle; and 3) habitat use of individuals throughout the nonbreeding period. We retrieved 7 tags from 30 tagged individuals following 1-year deployments. We found that four Alberta individuals overwintered in the Mississippi Alluvial Valley, two Alaska individuals overwintered in either the Great Plains or the Mississippi Alluvial Valley, and the single New Hampshire individual overwintered on the Southeastern Coastal Plain. Length of annual cycle stages varied among individuals, with the combined migratory periods occupying between 12% and 48% of the annual cycle. Stopover behavior was also widely variable, as minimum convex polygons of stopovers ranged from < 1 hectare to 505 km² and stopover durations ranged from 1 to 35 days (n = 40 stopovers). Birds predominantly used woody wetlands and emergent marsh during the nonbreeding period, but habitat use differed between roosting and foraging. Marshes were used more for nocturnal roosting, whereas woody wetlands were used for diurnal foraging. Our results can help efforts to conserve this declining species by targeting regions and habitats at specific times of year for management during the nonbreeding period. In particular, the large amount of time spent during migration periods suggests conservation efforts in stopover regions are just as important as those on the wintering grounds. Connectivité migratoire et phénologie du cycle annuel chez le quiscale rouilleux (Euphagus carolinus) révélées par les balises GPS archivéesRÉSUMÉ. La compréhension des habitudes de déplacements spatiaux et temporels des oiseaux migrateurs tout au long du cycle annuel peut permettre d'identifier les menaces potentielles pour ces populations. L'utilisation du comportement et de l'habitat des oiseaux pendant les périodes de migration et d'escales est particulièrement sous-étudiée chez de nombreuses espèces. Dans cette étude, nous avons utilisé des balises GPS d'archivage à haute résolution spatiale pour suivre les quiscales rouilleux (Euphagus carolinus) d'une population de reproduction de l'est du pays (New Hampshire) et de deux populations de l'ouest (Alaska et Alberta) tout au long du cycle annuel. Nous cherchions à déterminer : 1) la connectivité migratoire des trois populations distinctes ; 2) la phénologie migratoire, le comportement et le temps consacré à chaque phase du cycle annuel ; et 3) l'utilisation de l'habitat par les ind...

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In the past, monitoring hunting behavior has been limited to self-reported numbers. However, the ability of autonomous recording units to monitor soundscapes may make them suitable for assessing spatio-temporal shooting patterns. Our goal for this project was to find out if it is possible to use acoustic monitoring to track human activity, and if there were differences in seasonal or daily shooting intensities. We hypothesized that shooting intensity would decrease from September to November and from the afternoon till morning due to people being less likely to go shooting in cooler temperatures. A grid of 91 ARU’s were deployed between September 2nd and November 30th, 2018 in Cooking Lake-Blackfoot Provincial Recreation Area. They were set to record continuously between sunrise and sunset with some recording during the night as well. We selected a random subset of 30 minute recordings, visualized them using spectrograms; visual representations of sound with time on the x-axis and frequency on the y-axis, and counted the gunshots in each. We compared differences in gunshot detections between months and different times of day using analysis of variance (ANOVA). There were no statistical differences found in seasonal or daily shooting intensities. One reason for this may be that sample sizes were low, due to the time needed to manually process recordings. We demonstrated that ARU’s can be used to provide us with an accurate way of assessing shooting patterns and therefore, be useful for monitoring other human behaviors such as detecting poachers, or assessing compliance with hunting laws.