Date: 9/13/17 12:51 am
From: Tim Janzen <tjanzen...>
Subject: [obol] Re: Malheur Narrows Egrets
Dear Matt,

In my opinion, the dusky blue coloration in the wings seen in photo ML68686581 at http://ebird.org/ebird/view/checklist/S39142883 trumps the fact the bird has black on the legs. I don’t think that a Snowy Egret can ever show as much blue coloration as is seen in the bird in this photo. There are other features on this bird that also suggest LBH. The overall bill coloration and the thickness of the bill are also strongly suggestive of LBH and not of Snowy Egret. The legs of the bird in photo ML68686611 seem consistent with LBH in my opinion. They are basically greenish yellow. The bill coloration in photos ML68686611 and ML68686621 is also consistent with LBH. Another reference that reviews field marks for immature Snowy Egrets and Little Blue Herons is Ken Kaufman’s book “Advanced Birding”. In that book on p. 35 Ken states that “The plumage of Snowy Egret is all white at all stages, but the Little Blue is never pure white: even in the youngest immature the tips of the outer primaries are gray.” I see no reason to think that either bird (assuming that two different birds were photographed) must be a hybrid. I think that light conditions are making the bill of the bird in ML68686611 appear more yellow than it really is. The photo appears to have been taken late in the afternoon. The bill is far too long for a Cattle Egret.

Sincerely,

Tim Janzen



From: Matt Cahill [mailto:<matt.c.cahill...>]
Sent: Tuesday, September 12, 2017 11:12 PM
To: Shawneen Finnegan
Cc: Jeff Gilligan; Tim Janzen; OBOL
Subject: Re: [obol] Re: Malheur Narrows Egrets



Hi all,

I went back out to see the hegrets this afternoon, to watch them interact and take a few more photographs. I expected to confirm my doubts about the (potential) little blue, instead I walked away doubting the (potential) cattle egret even more. Back home in Bend, I read this thread and some additional resources and developed my own theory. Read on if you're still enjoying this ID challenge as much as I am.

David Sibley has a very helpful article (I think) on differences between snowy egrets and juvenile little blues, the only difficult heron ID in his opinion. The article is here: http://www.sibleyguides.com/2012/08/distinguishing-immature-white-little-blue-heron-from-snowy-egret

He writes extensively about how habit is a very useful ID trait. In short summation, both of the mystery hegrets behave much more like little blues than snowies (so I think). But more definitively, Sibley writes that little blue heron "wingtips show small dark gray tips on outer primaries...[and] are diagnostic". Both birds do show this trait in some of my photos, one more extensively than the other. See the fourth photo from yesterday's checklist (I added more from my SLR): http://ebird.org/ebird/view/checklist/S39142883

Sibley continues that the "presence of black [on the legs] is diagnostic for Snowy Egret, as is contrasting yellow feet." Both birds show nearly identical leg and foot coloration: a complex pattern of yellow and black. But definitely black. See today's checklist for a good comparison: http://ebird.org/ebird/view/checklist/S39154699

These two traits are contradictory. Both birds have 'diagnostic' qualities of both snowy egrets and little blues, with habit supporting LBH's. But to further complicated it, the 'cattle egret' individual has a very yellow bill which if looked at in isolation (along with the surrounding gape) looks very much like a cattle egret, to me. Sibley writes that snowies have a "bill usually darker [than LBHs] with blackish on culmen extending back close to forehead". Sifting through Google Images, I can't find any photos of LBH's or Snowies of any age having such a yellow bill as the 'cattle egret' individual.

Interestingly, it is easy to find pictures of juvenile Cattle Egrets with similar leg patterns as both of our individuals. Which leads me to a theory I'll offer. Could it be that both of these birds are Cattle Egret x Little Blue Heron hybrids? Such a hybrid could show the same leg and foot pattern, wing pattern, and variety of bill shapes and colors as our friends at the Narrows. Could it be even further that these two birds are nest mates? It doesn't seem completely beyond logic that a little blue and a cattle egret, both near the edge of their range and finding no appropriate mate instead found each other. Then their offspring found an incredible bounty of dying carp at the Narrows. I could be reading into it, but the birds seem to like each other, in a sibling rivalry kind of way!

In short, I don't see how we can claim either bird is a pure Snowy Egret, Little Blue Heron or Cattle Egret, at least not based on resources I've found. A far-flung Asian species is exciting, but seems harder to stick than a native hybrid. Putting the pieces together, this is the outcome I've found. Would love other's thoughts.

Thanks for reading!

Matt Cahill

Bend




 
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