Lesser Scaup
Aythya affinis
Adults are 38–48 cm (15–19 in) long, 41.7–43 cm (16.4–16.9 in) on average. The species can weigh 454–1,089 g (1.001–2.401 lb); males weigh 820 g (1.81 lb) on average while females weigh noticeably less, at 730 g (1.61 lb) on average. Wing lengths (not wingspans) are about 7.5–7.9 in (19–20 cm) in males and 7.3–7.8 in (19–20 cm) in females. The tarsus is about 1.4–1.5 in (3.6–3.8 cm) long, and the bill is 1.4–1.7 in (3.6–4.3 cm). The wingspan is 68–78 cm (27–31 in).
ID text from Wikipedia, CC BY-SA 4.0
Redhead
Aythya americana
The redhead is a pochard, a diving duck specially adapted to foraging underwater. Their legs are placed further back on the body, which makes walking on land difficult. The webbing on their feet is larger than dabbling ducks and their bills are broader to facilitate underwater foraging. In addition, pochards have a lobed hind toe. No pochard has a metallic colored speculum, something that is characteristic of other ducks. Voice: There is little information on redhead vocalizations outside of breeding calls. When the neck is fully extended in the neck-stretching display, males emit a cat-like wheee-oww. Males may also produce a soft coughing call, although this call is less frequent. Females emit a soft errrr note when inciting a male.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play BeakBrainPhotos and recordings are credited to their authors under the licence shown. Full profiles: Lesser Scaup and Redhead.