Sometimes placed in genus Nettion. Thought to be closest to A. andium and A. flavirostris. Race carolinensis sometimes considered a full species, and situation finely balanced. The male differs from nominate male in its vertical white breast-side line (2), lack of white horizontal scapular stripe (2), and lack of narrow buff supercilium (above broad green “eyestripe”) (1); various other very minor differences cannot be scored (plumage characters capped at three), differences in measurements do not exist, behavioural differences are matters of frequency rather than type#R, and genetic evidence, while suggesting paraphyly involving A. flavirostris#R, indicates that hybridization#R is relatively widespread in Beringia#R (possible score for broad hybrid zone 1), leaving carolinensis extremely close to species status. Aleutian race nimia judged very weak#R and here treated as a synonym of nominate crecca. Two subspecies recognized.
Food and feeding
Status and conservation
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