14 Sep 2014

14 Sep 14 - Revisiting The Aging Of The Studland Great White Egret

A few days ago, I posted a photo of the Poole Harbour Great White Egret at Littlesea, which has been hanging around the Studland area over the last week. This photo shows buff outer webs to the secondary coverts and buff tips to the secondary median coverts, which I've not seen in the field before. Additionally, I've not found any reference to this in the handbooks & field guides I've looked at. All the handbooks & field guides seemed to agree that Great White Egrets could only be aged on bare parts & the plumage was uniform white. All the photos I've looked on line, seem to show gleaming white wings.
Great White Egret: Littlesea, Studland (9 Sep 14)
Great White Egret: Note, the buff outer webs to the secondary coverts and tips to the secondary median coverts
As I was struggling to find any information about buff markings, I circulated the photos to a few friends for comment. The responses have been: Brett Spencer was on a bit of a learning curve, but guessed that it is a juvenile, as he thought there would be some moult visible, if it were an adult. Also, Brett expected there would be a difference in feather tip shape on the primaries, with juveniles perhaps showing a slightly pointier feather tip. Brett thinks he has seen similar brownish colouration on juvenile Little Egrets. James Lidster didn't remember seeing this in Great White Egrets before, but thought it occurred more frequently in Little Egrets. Martin Garner wasn't sure on this either, but felt it was probably a feature of fresh juveniles. Many thanks for Brett, James & Martin for allowing me to put them on the spot, responding quickly & having a go on this clearly difficult subject. 
Great White Egret: Note, the buff outer webs to the secondary coverts and tips to the secondary median coverts. Littlesea (9 Sept 14) 
Great White Egret: Blow up of the left wing. Littlesea (9 Sept 14)
I've spent a bit more time this afternoon, looking on line. I've not managed to find any other references to these buff wing edgings, but I did find a useful link on aging Great White Egrets in the US in late Summer from David Sibley. This web page is well worth a read. It confirms Brett's thoughts that juveniles would be expected to have really uniform coverts, primaries & secondaries as they are all fresh. It states that Great White Egrets do not moult their flight feathers, until they are one year old. So older birds would be going through their moult in late Summer & thus would have gaps in the flight feathers. 
Great White Egret: Whilst not close, it's closer than I've managed to get so far & the buff edgings are just about visible in the closed wing. Littlesea (14 Sept 14)
The best information that I've found on European Great White Egrets has been an online publication of the birds of Aragon, Spain by Javier Blasco-Zumeta & Gerd-Michael Heinze. Clicking on the Great White Egret link, will download an informative PDF file. This confirms the complete post breeding moult will be completed by November. Juveniles also go through a partial body feather moult which will also complete by November.
Great White Egret: Frustatingly, it flushed when I was walking back, was behind vegetation & going away from the bird at 150 metres. Whilst not sharp, it does show the uniform feathers on the left wing. Littlesea (14 Sept 14)
Bare part colouration will separate a breeding adult as that shows a black bill with contrasting blue-grey or lime-green lores, with black legs & feet & yellow on the tibia as far as the 'knees'. But outside of the breeding season, the bill reverts to the typical orange-yellow colouration. Keith Vinicombe's excellent Helm Guide to Bird Identification, states that juveniles are similar to adults with orange-yellow bills and black legs & feet with the extent of the yellow on the tibia varying between individuals. HBW and Herons Handbook by Handcock & Kushlan indicates that juveniles would have a black tip to the bill. The Handbook of Bird Identification for Europe & the Western Palearctic states juveniles will have initially have a yellowish-grey bill. Therefore, the story doesn't appear to be consistent, but it looks like juveniles are likely to have a dark tip, but it suggests this will change to orange-yellow reasonably quickly, given some sources don't mention it.

On balance, I think that the uniform flight feathers indicate this must be a juvenile bird. Looks like the bare parts might not really help at this time of the year. So the obvious next question is whether the Studland bird is showing an unusual coverts patterning or is this something that has been overlooked in the past. This wouldn't be surprising, given Great White Egrets seem to be quite a shy, wary species & not a relatively confiding species like the local Little Egrets are. Despite several attempts I've not managed to get close to this bird yet.
Great White Egret: Whilst not sharp, it does show the uniform feathers, except for some wear to one primary feather in the right wing. Littlesea (14 Sept 14) 
I also posted an email on the Dorset email group about these markings and that's when this whole subject went in a different direction, to the one I was expected. I had an email from West Bexington stalwart, Mike Morse, of a Great White Egret that flew past West Bex on the 24 July this year. This shows the same buff edgings as the Studland.
Great White Egret: Many thanks to Mike Morse for allowing me to post a picture of the West Bexington bird. Copyright of this photo remains with Mike. (24 July 14)
Great White Egret: Cropped & sharpened left wing. Copyright of this photo remains with Mike Morse. (24 July 14). There appears to be some lack of uniformity on the primaries, but as this isn't shown on the right wing, I'm assuming this might be individual feather damage rather than moult (as I would expect evidence of moult to be seen on both wings)
Mike's photo is fascinating (do I really mean that White Herons are fascinating???). This shows the buff edgings continuing onto the primary coverts. But the buff markings, do not appear to be as bold as on the Studland bird. It also shows some lack of uniformity on the primaries, but only on the left wing. Therefore, it's not the same bird as the Studland bird, despite being assumed to be the same bird that was later seen in the Weymouth area (& thus apparently heading in the Poole Harbour direction).

I think both birds are probably juvenile birds, based on the overall conditions of the wing feathers. But this buff markings to the wing coverts in Great White Egrets doesn't appear to be something restricted to a lone individual. I would really appreciate any thoughts on these conclusions and feedback on other Great White Egrets which show buff markings to the wing coverts, as I'm sure there must be more to learn here.

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