Friday, March 21, 2014

Hybrid "Presumably" Brant X Cackling Goose in New York City...

A hybrid goose was reported at Randall’s Island by Anya Auerbach, on March 16th. Apparently it was not a first time visitor, but rather a repeat one with the first documented sighting in 2003 by Angus Wilson. Subsequent to Angus' report, it showed up intermittently in the New York City area with all previous observations at Corona Park Queens. In 2008, it was observed, and photographed by birder/photographer Pete Chen and in 2011, by Steve Walter. Shai Mitra, one of our state’s foremost expert on all things with feathers, did some analysis on the photos from Pete Chen back in 2008 and suggested then, that the bird looked good for a hybrid Brant X Cackling. His proposed identification was based on the following features that he noted:

  1. The breast is concolorous with the flanks and decidedly browner than the black neck--just as in Cackling and Canada geese, but differing markedly from Brant's (and Barnacle Goose's) extensive, black neck stocking.
  2. The characteristic white neck markings of Brant are absent. 
  3. There is a hint of whitish cheeks, on both sides of the face, as in Cackling and Canada geese. 
  4. The tail is extensively black beyond the coverts, as in the white-cheeked geese, but unlike Brant.

Here you could see the extensive black beyond the coverts (see # 4 above for more details).
Shai, further suggested that even if the identification was correct, both proposed parental species were polytypic, so questions surrounding which taxa were involved are unanswered. He proposed that hrota x hutchinsii would seem the best bet, purely on geographical grounds, but then brings our attention to the bird’s ventral plumage, which is much darker than in either of the forms mentions. He also uses the structure of the bird suggesting that the petite and small billed look was perhaps too much for one of the parents to be hutchinsii. However, if the bird originated farther west, then perhaps nigrans x minima could plausibly produce such a hybrid of this appearance. He rounds out the possibilities for Brant parentage by referencing, “Gray-bellied Brant,” which breeds in the western Canadian high arctic, and which has possibly occurred on Long Island as a vagrant, suggesting it ought to be considered, as should bernicla, which has been reported several times on the East Coast, including long Island.

This was an excellent analysis from Shai, but before deciding if you agree, you should read this equally top notch analysis from Angus Wilson, when he first documented this bird in 2003.  Angus, presents the theory of a Brant x Canada with solid reasons. You should also take a look at the comments area where birders from around the world offered their opinion.

When I first saw the photo of this bird, I thought the breast was too dark for it have Cackling parentage and like Angus thought it looked more like the presence of Canada,  but after studying it in the field and getting photos of my own, I am leaning towards a hybrid of Brant x Cackling.  This is a a fascinating bird and one that was worth standing over an hour in the freezing cold and windy conditions at Randall’s Island before I was able to study it at length and obtain some photos, which I have provided for your viewing pleasure. Thoughts on this bird are most welcome. Tags: , , , Share with Bookmark and Share

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