Timing of molt is a critical life-history trait because molt is a nutritionally demanding process that must be completed before fall migration. We used data from 1992-2008 to assess hypotheses that initiation of the prebasic molt by Black Brant (Branta bernicla nigricans) was ultimately controlled by (1) the need to complete the molt before fall migration and (2) advantages of restoring depleted nutrient reserves before growing feathers. Specifically, we expected molt to occur sooner after hatching in years when nesting was delayed (prediction 1), but we expected individuals to delay molt in relation to hatch date when nesting was earlier (prediction 2). Our rationale for prediction 1 was that the need to complete molt before fall migration is exacerbated when nesting is delayed. Prediction 2 is suggested by the advantage of restoring nutrients depleted during nesting before initiating molt. We tested predictions by assessing patterns of ninth-primary length in relation to number of days posthatch, modal hatch date, and relative hatch date within years. We calculated molt initiation dates using parameter estimates from the best-supported model, using lengths and growth rates of ninth primaries. We estimated that Black Brant initiated molt an average of 14.5-19.5 days posthatch, depending on year. For modal hatch dates before 22 June (summer solstice), date of mean initiation of molt was negatively correlated with modal hatch date (b = -0.56), whereas for modal hatch dates after 22 June, mean initiation of molt began an average of 16.1 days after hatch. In years when modal hatch date was before 22 June, Black Brant waited longer after their clutches hatched before beginning molt, which suggests an advantage of greater stored nutrient levels before initiating molt. By contrast, in late-nesting years, Black Brant began molt 16 days after they hatched their clutches, which suggests that (1) a minimum average period posthatch was required before molt commenced and (2) there was a cost of further delay in molt in late-nesting years. Declining photoperiod following the summer solstice is a reasonable candidate for the signal that Black Brant use to initiate molt in late-nesting years. Ritmo de Muda de las Remeras en Hembras Adultas de Branta bernicla nigricansResumen.-El ritmo de la muda es un rasgo crítico de la historia de vida porque la muda es un proceso nutricionalmente demandante que debe ser completado antes de la migración de otoño. Usamos datos desde 1992 a 2008 para evaluar las hipótesis de que la iniciación de la muda pre-básica de Branta bernicla nigricans está controlada de manera última por (1) la necesidad de completar la muda antes de la migración de otoño y (2) las ventajas de recuperar las reservas de nutrientes antes del crecimiento de las plumas. Específicamente, esperábamos que la muda ocurriera poco después de la eclosión en años en que la anidación fue retardada (predicción 1), pero esperábamos que los individuos retrasaran la muda en relación con la fecha de eclosión cuando la anidación sucedió t...

Impacts of anthropogenic disturbance on duck populations in the boreal forest is largely unknown but hypothesized to negatively influence abundance through top-down and bottom-up processes. We examined relationships between population trajectory of duck pairs and anthropogenic disturbances in the Boreal Plains ecozone of western Canada by first controlling for habitat and then assessing whether population trends were related to density of seismic lines, pipelines, roads, and well sites, and distance to agriculture to help focus conservation efforts on the most limiting changes. We also evaluated whether these relationships differed in agriculture encroached vs. unencroached landscapes; distance to agriculture was assessed in unencroached landscapes. Pair counts obtained from the Waterfowl Breeding Population and Habitat Survey were pooled into nesting guilds (cavity, ground, and overwater). All anthropogenic disturbance features were time invariant. Annual moisture data was used to control for effects of annual variation in breeding season weather. Variation in relative magnitude and direction of effect size indices among anthropogenic disturbances depended on both landscape and nesting guild. Overall, majority of negative relationships occurred with seismic lines and pipelines, while distance to agriculture was positive. Population trends for ground nesters, which suggest overall declines, tended be most negative in regions with high seismic line and well pad density in encroached landscapes and with high seismic line and pipeline density in unencroached landscapes. Cavity nester population trends were generally positive throughout the study area but were lowest in unencroached landscapes farthest from agriculture. Overwater nester trends were generally lowest in encroached landscapes with high densities of seismic lines, roads, and well pads and in unencroached landscapes with high densities of seismic lines, pipelines, and roads. Although our work suggests that anthropogenic disturbances, particularly seismic and pipelines, may merit further consideration as foci for conservation, additional research is needed to quantify demographic implications. Évaluation des tendances de population de canards nicheurs relativement aux perturbations d'origine anthropique dans les Plaines boréales du Canada, 1960-2007RÉSUMÉ. Les effets de perturbations d'origine anthropique sur les populations de canards nichant en forêt boréale sont grandement inconnus, mais on les soupçonne d'influer négativement sur l'abondance des canards par l'action de processus ascendant et descendant. Nous avons examiné les relations existant entre les tendances de population de canards nicheurs et les perturbations d'origine anthropique dans l'écozone des Plaines boréales dans l'ouest du Canada, en contrôlant pour l'habitat dans un premier temps, puis en évaluant si les tendances de populations étaient liées à la densité de tracés sismiques, de pipelines, de routes et de puits, et à la distance aux activités agricoles, afin de contribuer à diriger ...

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Waterfowl rely on breeding habitat availability for successful reproduction. Breeding habitat availability likely changes throughout the season and among years as weather patterns change and thus productivity rates are likely susceptible to these changes. We used data from 1961 to 2011 to investigate effects of weather, breeding habitat availability and abundance of breeding mallards (Anas platyrhynchos) on productivity rates of mallards breeding in the Great Lake states (Michigan, Minnesota, and Wisconsin; hereafter GLS). We hypothesized that productivity rates would increase with wetter and warmer conditions however, extreme temperatures may have a negative impact and that high breeding density may negatively impact productivity rates. Specifically, we looked at the effects of average June and July temperature and precipitation, the Palmer Hydrological Drought Index (hereafter PHDI), and wetland counts to model productivity rates across the three states for the time series. We used a reduced time series model set to evaluate the impacts of wetland counts on productivity. We found that in general, wetter conditions, as indexed by high positive PHDI values and relationships with pond abundance, positively affected productivity. We believe that breeding habitat availability is likely a reasonable predictor of mallard productivity rates in the GLS.