Eurasian (Common) Teal X American Green-winged Teal hybrid

Horizontal scapular stripe
Eurasian (Common) Teal: Bold horizontal white stripe. The lower scapular feathers have a black outer web and a broad white inner web. It is this white inner web of the scapular feathers that produced the horizontal white stripe on the Eurasian Teal. Sometimes the lower gray side feathers cover a portion of the white stripe. Usually, however, the stripe is very obvious, and the white is wider than the black.
American Green-winged Teal: The black outer web of the scapular feathers may be visible, but are usually not obvious. The inner webs are brownish gray and do not contrast boldly with the back. Thus, the American form never shows a white scapular stripe.
Hybrid Teal: Often have a white and black horizontal scapular stripe. However, the white is narrow and often restricted primarily to the middle of the sides. In summary, the white stripe is both narrow and short.

Vertical white breast bar
Eurasian (Common) Teal: Absolutely no hint of a vertical white bar on the side of the breast.
American Green-winged Teal: Bold vertical white bar from shoulder downward across the side of the breast.
Hybrid Teal: Often faint vertical white bar from shoulder downward across the side of the breast and may be invisible in the field at some angles.

Creamy face markings
Eurasian (Common) Teal: Bold creamy lines on the face outline the base of the bill and extend over and around the green patch on the side of head, as well as outlining the underside of the green ear patch. The creamy lines are obvious above the green ear patch to well back of the eye.
American Green-winged Teal: A short white line is usually obvious on the underside of the green ear patch, under the eye.
Hybrid Teal: Usually faint creamy lines on the face outline the base of the bill and on the underside of the green ear patch, below the eye.

Minor Supporting Characters
The following characters may support the identification, but never overrule the three major identification criteria above.
•Head color: The red head of American Green-winged Teal is a darker chestnut with almost blackish forehead and chin.
•Breast color: Eurasian (Common) Teal is paler whitish-buff with sparser spotting, while American Green-winged Teal often has a slight pinkish hue.
•Undertail color: Eurasian (Common) Teal has brighter "lemon-yellow" sides to the undertail whereas American Green-winged Teal can appear darker cream yellow.
•Speculum border: The leading border on the speculum of the wing is buff on American Green-winged Teal. The border is white on Eurasian (Common) Teal, narrower at the base of the wing and wider toward the wrist. This is true for both males and females and is the primary diagnostic mark on females.
•Side vermiculations: The sides of American Green-winged Teal are smoother, darker gray. The sides on Eurasian (Common) Teal often appear paler because of the coarser gray and white wavy lines on the feathers, visible at close range.
•Pale bar on flank: There is a pale bar in front of the black sides of the undertail coverts on Eurasian (Common) Teal. It is reduced or lacking on American Green-winged Teal. Hybrids are variable.
•Head shape and size: American Green-winged Teal appears to have a fuller head than Eurasian (Common) Teal and may have slightly elongated crown and neck feathers creating a narrow ponytail.
•Tertial pattern: American Green-winged Teal pale evenly grey tertials with distinct darker shaft stripes whereas Eurasian (Common) Teal has a more diffuse dark grey pattern being darkest along the shaft and gradually becoming paler towards the edges.
•Tail length: American Green-winged Teal has longer central tail feathers than Eurasian (Common) Teal.

The face lines are reduced to a creamy crescent at the base of the bill and a white line under the eye.

The slightly elongated crown and neck feathers creates a narrow ponytail.

Note the difference in the undertail pattern between the two males in the video below. In the hybrid (behind) the length of the exposed tail feathers equals that of the black undertail band whereas the shorter tail in Eurasian (Common) Teal (in front) projects only half the length of the black triangle.



In Eurasian (Common) Teal the black pattern on the undertail creates a pointed triangle whereas the hybrid has rounded tip instead of a pointed hind corner.