Eastern Spotbilled duck: Bird of the Week XII

That couldn’t possibly be an Indian spot-billed duck, could it? We were in the middle of Tokyo, after all. No, it was the Eastern spot-billed duck (Anas zonorhynchus) which does not have the orange splash at the top of the bill, near its nostril. Shinobazu pond inside Tokyo’s Ueno Park, where we saw it, is in the middle of the range of this species. To the west their range overlaps their Indian cousins’ along the foothills of the Himalayas, and in the north their range has been expanding well into Asian Russia, possibly as a result of global warming. The result is that it has begun to hybridize with the mallard in Russia. Interestingly, males of the spotbill are more likely to mate with female mallard than the other way around. A closer look at this phenomenon reveals that female ducks are fairly true to their breeding sites, while males range widely. This asymmetric dispersion results in the males having more out-breeding opportunity, if you can call it that, and produces the asymmetric hybridization that is observed. But such hybridization shows that speciation amongst dabbling ducks (the genus Anas) is fairly recent and could be ongoing. Who knows, perhaps the bird watchers of a hotter world could have new dabbling ducks to see!

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An invitation

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There aren’t many places on WordPress where bird watchers can share posts. If you post any photos of birds this week (starting today and up to next Monday), it would be great if you could leave a link in the comments, or a pingback, for others to follow. There is no compulsion to post a recent photo, but it would help others to know when and where you saw the bird. You might consider using the tag “Bird of the Week” in case people search for old posts using it. I hope you’ve had the time to look at what others have added this week and in the previous weeks.

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