Black Duck - Mallard Comparison,
USFWS
posted to en.wiki by <a href="https://en.wikipedia.org/wiki/User:Jimfbleak" class="extiw" title="en:User:Jimfbleak">Jimfbleak</a> at <a href="https://en.wikipedia.org/wiki/File:Blackduckmallard7.jpg" class="extiw" title="en:File:Blackduckmallard7.jpg">Blackduckmallard7.jpg</a>, original source unknown