Seasonality at the equator: isotope signatures and hormonal correlates of molt phenology in a non-migratory Amazonian songbird.

摘要: Birds, across their annual cycle, progress through sequences of life-history stages such as reproduction and molt. The mechanisms that control avian itineraries involve endocrine responses triggered by seasonal environmental factors, including changes in resource availability and/or photoperiod. However, at equatorial latitudes birds are exposed to different degrees seasonality, the underlying phenology near equator remain less explored. We studied silver-beaked tanager, an endemic Amazonian songbird, from lowland population. Remarkably, this species, song behavior has been shown be seasonally aligned minimal day length equator. Here, we aimed further explore tanagers assessing shifts food sources utilization potential ultimate factors. measured triple isotopic tracers carbon (δ13C), nitrogen (δ15N) sulphur (δ34S) blood feathers throughout a whole year. In addition, assessed degree seasonality molting activity, relation circulating levels corticosterone, well testosterone proxy reproductive condition males. There was important variation δ34S values rainfall patterns estuarine water composition. Despite rainfall, found no substantial foraging ecology over seasons. This accompanied uniform corticosterone year, probably associated with absence drastic shortages. Even so, showed marked schedule, which related both testosterone. These findings suggest niche is not life history stage-dependent tanagers, highlight cue for bird phenology. Our stable isotope results encourage studies addressing influence dynamics on timing. primary role steroid hormones regulating under Contrary what might expected tropical our physiological data do support reproduction-molt overlapping.