Resource allocation effects on the timing of reproduction in an avian habitat specialist

Variation in nutrient allocation can influence the timing of breeding and ultimately reproductive output. Time space constraints might exist, however, if fewer food resources are available to meet costs reproduction early during season. Here, for first time, we test whether nutrient-allocation strategies a shrub-dependent avian species differ with different ecoregions: high-elevation landscape, containing spatially complex vegetation (Rocky Mountains) vs. low-elevation, more homogenous landscape (Great Plains). We analyzed data collected from radio-telemetry stable isotopes assess degree which endogenous (body) reserves used variation was associated time year, ecoregion, habitat quality (including sagebrush type plant greenness), or maternal characteristics. Using Bayesian statistical framework, found that females relied on similar amount nesting renesting attempts. Additionally, contributions declined rapidly throughout season Rocky Mountains than Great Plains. Individuals high- intermediate-elevation types amounts reserves, whereas low-elevation less. Females at intermediate elevations, experience greatest flush new green season, switched their reliance endogenous-to-exogenous sources as became spring. Our study highlights adaptations strategy across areas varying levels specialist bird. Nutrient by individuals residing favors mainly uses nutrients gained wintering habitats, use exogenous reproduction.