|Cinnamon Teal female. Santee Lakes, California. October 11, 2013. Greg Gillson.|
That quiz was based on shape. Many hen ducks can be identified by shape alone, while the brown camouflage plumage isn't all that distinctive and can be confusing. Two ducks that are very similar in shape are Blue-winged and Cinnamon Teal. Both have blue wing patches and the brown-patterned females are very similar. The subtle pattern on the face is the best way to tell them apart.
The face of the Cinnamon Teal is buffy-brown and rather plain. The crown and lower cheek is slightly darker. There is a hint of a broken eye ring, but it is not obvious.
|Blue-winged Teal female. Santee Lakes, California. October 11, 2013. Greg Gillson.|
Not all individuals are as obvious as these two, And birds in their first year are much more similar. But with practice, you should be able to identify these look-a-likes more frequently with increasing confidence.