Re: Unidentified duck at San Lorenzo Creek/Reservoir
On 3/21/2021 10:07 PM, Lawrence Danos wrote:
Hi, Two of us were birding Saturday along San Lorenzo Creek near where it enters SF Bay (lower San Lorenzo Creek). Today (Sunday) we were at Don Castro Reservoir (upper San Lorenzo Creek} In both places we noticed several pairs of mallards but there was one pair, a male mallard and a black duck with white breast were paired together. In both cases they were hanging out together with the other mallard pairs and swimming together as is usual in the Spring. I couldn't get close enough to get a picture but am wondering if anyone else saw these two and what is the black & white duck? It's about the same size as a mallard and completely black except for the white breast.
Basically, if it looks like a mallard and associates with mallards, it's a mallard. The situation is rather like what we have with dogs - very very occasionally you do see a real inter-species cross, but mostly you get the results of millennia of domestication. The vast bulk of the world's domestic-duck population is based on mallard stock, and every drake regards every duck as a possible mate regardless of distance from the wild (or lack thereof) - and the ducks mostly agree, though they'd rather avoid the young hoodlums.
Ducks do form true hybrids - like the Barrow's Goldeneye x Hooded
Merganser we had at Lake Merritt for a few years
- but among mallards what you get are mostly just crosses: the
cockapoos of the bird world rather than the wolf dogs.
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