The Garganey is rare summer visitor to the UK. To make finding one more difficult, they like lurking in the reeds, and they quite small (only slightly larger than a Teal). However, when you do see a male Garganey, it is very distinctive, having a very large white eye stripe, that extends all down its neck. Like most ducks, the female has much more subdued plumage and a less much distinct pale stripe above and below her eye.

The photo below shows the somewhat less flamboyant female Garganey...