Greater Scaup, Lesser Scaup or hybrid?

UPDATE:
I've obtained several comments. Greater Scaup was dismissed as the bird on photo is smaller and head shape is different. Lesser Scaup would be extremely rare but the bird on the photos is missing texture on its back, tip of its bill is extensively black so Lesser Scaup could be dismissed too. Most probably it is a hybrid of Tufted Duck and Pochard that are abundant in the area. Most of the comments are saying about hybrid. I compared photos of other birds of these hybrid and it seems very similar. This not 100% conclusion but we are probably very close to truth. Thank you for your contribution!

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I wrote about my latest birdwalk along Danube below Bratislava here. I found 4 Scaups (1 male and 3 female). I have identified all of them as Greater Scaup (Aythya marila). I made photos only from that male but it was questioned on Twitter that it has a bit odd shape of head. Hrušovská zdrž water reservoir on Danube River (IBA Dunajské luhy) is regular wintering site of Greater Scaups (30-100 birds). Aside of this species man can find here during the winter 20000-30000 Tufted Ducks (Aythya fuligula) and few thousands of Common Pochards (Aythya ferina), but Pochards are in decline. I made few photos using my HTC Desire S phone and 20-60x cheap spotting scope. All the photos are without any postproduction, just cropped. I made also one video. I'll be thankful for your opinions on identification of this Scaup. Please write a comment, mail me (tomas.novak@ymail.com) or tweet me (@titodaking)

Tu som písal o mojej vychádzke k Dunaju. Na Twitteri mi bolo poznamenané, že tá Aythya marila má zvláštny tvar hlavy. Fotené je to telefónom HTC Desire S, ktorý bol priložený k lacnému monokuláru 20-60x z Lidla. Na fotkách nie je žiadna postprodukcia iba som ich orezal. Podarilo sa aj jedno krátke video. Čo vy na to? Budem vďačný za akýkoľvek názor. Prosím napíšte mi komentár, mail (tomas.novak@ymail.com), tweet (@titodaking), alebo pridajte koment k pozorovaniu na birdingu.