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Hi all.

Can someone educate me on this. I was under the impression Scaup never had a white bum and if so its probably a White Eyed Duck. Spotted this chap at the Christchurch-Bromley oxidation ponds this afternoon and thought I'd lucked out on a White Eye but the beak certainly isn't a white eyed duck as far as I can tell. As usual waaaaaaaaay over the back of the ponds so sorry for crappy shots.

I have just received the following email from PaulG

Interesting post from 'Adam C' about a white-undertail on a Scaup at Bromley Oxidation Ponds. I was scoping that bird up intensely earlier this week. You could tell him from me that the bird has been there since the summer (I also looked at it hard in Feb and March), and there's a similar individual up at Travis Wetland that is usually visible in front of the hide. Dunno how this characteristic comes-about, but it certainly grabbed my attention during my five week countrywide expedition in search of Hardheads in Feb/Mar/April !

Cheers, Grahame

On 16th June 2018, among 158 Scaup on the ponds in Balclutha, there were five with significant white on undertail coverts. There were no other characters of White-eyed Duck. Poor photo at https://ebird.org/newzealand/view/checklist/S46578509

Interesting. Thanks for the info both.

I think Richard's observation is fairly typical with this plumage in female NZ Scaups occurring regularly though in the minority. I've always assumed it had something to do with fresh basic/winter plumage but have never properly looked into it (it seems most adult females have at least some white spackling in the undertail). In general the white bum appears closely tied to very prominent white lores. Visit anywhere with big numbers of scaup (eg Rotorua) and there will be a handful of females like this bird. Clinton any ideas?

Great example of how a single feature cannot make a bird. Well-sussed Adam.

Russ