Cape May, last Friday. This looks similar to a female Mallard, but I'm wondering if it is a male Gadwall in some sort of juvenile or transitional plumage. Other Gadwalls on the pond that day were in breeding plumage, but this one looks similar to the male Gadwall (Eclipse plumage) shown in Vuilleumier's Birds of North America. I thought Eclipse plumage occurred at the end of the breeding season, rather than the beginning, so I'm not so sure; but the fine feather pattern on the flanks looks to me like a Gadwall. Any suggestions?
Yes, it's a male Gadwall. You are correct about the barred flanks. Another thing to look at is the mostly black undertail, a mark mark for Gadwall.
Another mark is the bill pattern. A female type Mallard has sort of a dark saddle over the middle of the bill. A female (and perhaps immature?) Gadwall has dark running down the length of the top of the bill. That might be a key to the age of the bird, but I don't know enough about molting ducks to say.
Recent research has turned the whole concept of "eclipse" plumage kind of on its head. I don't have the details down since I haven't reviewed this in depth, but here's a rough go of it. The bright and pretty male plumage we all know and love to photograph is apparently the birds' "basic" or winter plumage. On the breeding grounds, particularly when they molt their flight feathers, they are drabber and thus in their "breeding" or summer plumage, which is what "eclipse" referred to. This makes sense since if you're nesting and/or flightless, you don't really want to call attention to yourself.
Bill- Gadwalls should have moulted into their Basic plumage by now, and look spectacular after they have done this. Your bird looks pretty rough! I wonder if it's a young male. Waterfowl are outliers in the bird world for a couple of reasons, and probably more. Paul has mentioned one, their moult. For whatever evolutionary reason, many (but not all) species of waterfowl pair up in the fall and stay paired through the winter. This fits nicely with their moult because they need to compete for, and attract mates in the fall, not in the spring like most birds, and so moult into the bright, Basic plumage in the fall. The second weird thing about waterfowl is which sex disperses. If animals didn't disperse from their natal areas, the chances of inbreeding would be much higher- the acorn not falling far from the oak tree so to speak. Inbreeding has genetic costs, although inbreeding with the right relative- not too close and not too distantly related- is actually beneficial in this regard. Anyway, animals generally avoid inbreeding with close relatives. If you think about it, only one sex needs to move away from where they were born to reduce inbreeding. In most bird species it's the female that is the dispersing sex. If you band, say gulls, as chicks at a colony, you will get many more male recoveries back at the colony in subsequent years than females. The female chicks you banded will be found in other colonies. In waterfowl it's the reverse with males returning far less to their place of birth than females. So a typical male waterfowl will pair up with a female in the fall, maybe on the wintering grounds, and then follow her back to her natal location in the spring.
Last edited by John Chardine; 10-28-2010 at 05:19 AM.
Waterfowl ID (Gadwall?)
Reply With Quote
