Autonomous recording units (ARUs) are emerging as a useful technology for the study and monitoring of animals that produce vocalizations. During summer and fall of 2013, we performed a series of experiments aimed at developing sampling protocols to count nocturnally active yellow rails (Coturnicops noveboracensis) from sound recordings. Field-based portions of the work took place in the rural municipality of Foam Lake, Saskatchewan, Canada, in an open landscape where yellow rails can be found during the breeding season; lab-based portions of the work occurred in Saskatoon, Saskatchewan, Canada. Our objectives were to 1) determine the frequency of yellow rail vocalizations to derive an empirically based sampling interval for counting individual birds; 2) assess the accuracy of yellow rail counts made from recordings; 3) determine the approximate sampling radius of the ARU for detecting yellow rails; and 4) determine the approximate audio volume ("loudness") of yellow rail calls. We developed a sonogram-based method for counting individual birds on recordings. Using field recordings of individual yellow rails, we generated recordings with known numbers of calling individuals (i.e., 1-12) and tested the accuracy of the sonogram-based counts. Regardless of experience, observers were able to determine the number of rails calling with a high level of accuracy, especially when the chorus was composed of 6 individuals. From broadcast trials employing multiple ARUs, we found the effective detection radius of calling yellow rails to be between 150 m and 175 m. Although detection radius was influenced by broadcast intensity and ambient conditions, we view this range of distance as a reasonable estimate of the effective sampling radius for the ARUs that we used, which is useful for deriving values of density estimates. Finally, we measured loudness of yellow rail calling at approximately 95 dB; this value is useful to research efforts attempting to mimic actual yellow rails (e.g., call-broadcast surveys, additional ARU experiments). A combination of the sonogramcounting method and baseline information on detection radius of the ARU provides a tool that will generate high-quality data on yellow rail occurrence, abundance, and density. Digital recorders represent a means to rapidly improve survey coverage of yellow rails throughout the species' range. Ó 2016 The Wildlife Society.

Postbreeding survival of waterfowl is rarely quantified, despite potential for constraints during this stage of the annual cycle that may subsequently affect population dynamics. We estimated survival of radio‐marked adult male Barrow's goldeneyes (Bucephala islandica) during remigial molt and fall staging at Cardinal and Leddy Lakes in the Boreal Transition Zone of northwestern Alberta, Canada. Daily survival rate (DSR) was high during remigial molt (DSR = 0.9987, 95% CI: 0.9967–1.0000), corresponding to a 39‐day period survival rate (PSR) of 0.95 (95% CI: 0.88–1.00). During fall staging, DSR was markedly lower (DSR = 0.9938, 95% CI: 0.9898–0.9978), corresponding to a PSR of 0.68 (95% CI: 0.53–0.87) over the 62‐day period between the end of remigial molt and fall migration. Half of fall staging mortalities observed on Cardinal Lake were directly attributed to hunting. We conclude that remigial molt is a period with high survival in the annual cycle of Barrow's goldeneyes at our study sites. However, in light of low fall staging survival, Barrow's goldeneye harvest management strategies should be carefully evaluated with intent to reduce risk of localized high mortality at significant staging sites in western Canada. © 2013 The Wildlife Society.

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Timing of seasonal bird migrations is broadly determined by internal biological clocks, which are synchronized by photoperiod, but individuals often refine their migratory timing decisions in response to external factors. Using 11 years of satellite telemetry data, we show that Pacific Barrow’s Goldeneye (Bucephala islandica), at higher latitudes, initiated spring and molt migrations later and fall migration earlier than individuals at lower latitudes. We further show that individuals refined migratory timing in response to interannual variation in environmental conditions. Individual Barrow’s Goldeneye initiated spring migration earlier in years with warmer springs at their overwintering locations and concluded spring migration earlier in years with earlier annual snow melt on their breeding grounds. Because individuals respond to conditions both where they initiate and where they conclude spring migration, our results suggest that Barrow’s Goldeneye update their migratory decisions en route. For all three migrations in their annual cycle, birds delayed initiating migration if they had been captured and tagged prior to that migration. Birds that initiated migration late for their latitude were less likely to include a stopover and completed that migration faster, partially compensating for delayed departures. Our results are consistent with the hypothesis that Barrow’s Goldeneye use a combination of endogenous cues and environmental cues in migratory decision making. Sensitivity to environmental cues suggests that Barrow’s Goldeneye may have behavioural plasticity that is adaptive when faced with ongoing climate change.

Molt is a metabolically demanding process in the annual cycle of birds, particularly for species that undergo simultaneous remigial molt because nutritional and energetic costs occur during a short period. Birds that molt remiges simultaneously utilize many different body-mass and foraging strategies to meet the nutritional and energetic costs of remigial molt, and documentation of interspecific variation has contributed to understanding species-specific risks associated with molt. However, little is known about intraspecific variation in body-mass and foraging strategies among birds that molt remiges simultaneously. We documented body-mass dynamics and foraging effort of Barrow's Goldeneyes {Bucephala islándica) during simultaneous remigial molt at two important postbreeding sites, including a large, hypereuthrophic lake and a small, mesotrophic lake in Alberta, to determine whether strategies for meeting nutritional costs of remigial molt varied across sites, years, and cohorts. Average body mass of all age and sex cohorts on both lakes increased during remigial molt in both 2009 and 2010. Birds were heavier on the smaller lake, and heavier in 2010 than in 2009, and adult males were heavier than subadult males. Radiomarked adult males exhibited similar foraging effort on each lake in each year (approximately 120-140 min day"'); however, birds foraged primarily diurnally on the large lake and nocturnally on the small lake. We conclude that Barrow's Goldeneyes exhibit considerable intraspecific variation in body-mass and foraging dynamics during remigial molt across sites, years, and cohorts, which suggests that these components of molt strategy are plastic and responsive to local environmental conditions. Variation de la masse corporelle et de l'effort d'alimentation de Bucephala islándica lors de la mue des rémiges RÉSUMÉ.-La mue est un processus du cycle annuel des oiseaux qui est exigeant sur le plan métabolique, particulièrement chez les espèces qui subissent une mue simultanée des rémiges car les coûts nutritionnels et énergétiques se produisent sur une courte période. Les oiseaux dont les rémiges muent simultanément utilisent diverses stratégies de masse corporelle et alimentaires afin d'assumer les coûts nutritionnels et énergétiques de la mue des rémiges. La documentation sur la variation interspécifique a contribué à la compréhension des risques spécifiques associés à la mue. Toutefois, on en sait peu sur la variation intraspécifique de la masse corporelle et les stratégies alimentaires chez les oiseaux qui subissent une mue simultanée des rémiges. Nous avons documenté la dynamique de la masse corporelle et l'effort d'alimentation de Bucephala islándica au cours de la mue simultanée des rémiges à deux importants sites de mue postnuptiale, soit un grand lac hypereuthrophe et un petit lac mésotrophe en Alberta, afin de déterminer si les stratégies pour assumer les coûts nutritionnels de la mue des rémiges varient entre les sites, les années et les cohortes. La masse corporelle moyenne de toutes les cohort...