Of the vital rates that determine recruitment, breeding propensity (i.e., the proportion of females that lay at least one egg) and nest success appear to have the greatest influence, but breeding propensity remains poorly studied. The few studies that have been conducted reveal it to be highly variable among years (15–77%), likely in response to environmental conditions (e.g., precipitation and wetland availability), and lower than estimates from other dabbling ducks. Thus, quantifying breeding propensity across the mottled duck range in the WGC and identifying factors responsible for its variation remain high priorities for future investigation. Breeding propensity is also among the most difficult vital rates to study, as it typically relies on intensive data collection from individual birds. However, recently light-level geolocators have revealed both regional movements of hen canvasbacks as well as their nesting activities, as evidenced by regular patterns of extended darkness during the day caused by the geolocator being obscured from sunlight during egg laying and incubation. (Light-level geolocators are devices that record data on the duration and timing of daylight as a means of calculating a geographic position.)
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