A number of combinations are possible and this is where things gets difficult! In discussion of this individual, and our knowledge of Aythya hybrids in general, I will focus exclusively on males. Hybrids in female-type plumage are poorly understood and thus remain extremely difficult to identify. 

Fig. 1. The hybrid (third from right) spent much of its time sleeping, only occasionally waking to threaten other males. Notice the charcoal gray back, immaculate white flanks and obvious 'tuft' projecting from the back of the head. Photo copyright of Angus Wilson.

Fig. 2-5. A selection of shots of the hybrid showing the tuft raised to various extents. Notice the pale band towards the tip of the bill indicative of Tufted Duck and neither of the scaup. In general the head shows a purplish sheen. From this distance the grayish vermiculations blur to create a charcoal wash across the scapulars. The iris was golden eye, similar to the Lesser Scaups. Photos copyright of Angus Wilson.

Male Tufted x female Pochard hybrids are well known in Europe and closely resemble Lesser Scaup. The key difference is that the hybrids show even finer vermiculations and have a more extensive black on the tip of the bill (Mullarney et al 1999). As far as I can tell, all birds with a discernible tuft are considered to be at least part Tufted Duck. In other words, no other combination throws out tufted progeny from untufted parent species. Ring-necked Duck has a peaked hindcrown but this does not really give the impression of a 'tuft'.

Randler (2001) includes a photo of a male Ferruginous x Tufted Duck which is also strongly reminiscent of Lesser Scaup but shows a white iris. The iris of the Massapequa appeared to be yellow, similar to the Lesser Scaups.

Fig. 6-7. More shots of the hybrid as it snoozed with Lesser Scaups. Again the tuft is clearly visible. Photos copyright of Angus Wilson.

A very similar bird is shown in Figures 12 and 13 of Mike Toochin's excellent review of the North American status of Tufted Ducks (Toochin 1989). Photographed by Vivian Keerd in Seattle in February 1991, this confiding male shows the same combination of finely vermiculated scapulars, snowy white flanks and a rather conical bulky short tuft. Both the Long Island and Seattle hybrids show a pale band across the bill, a feature of Tufted Duck. At the same time, the black nail is much narrower than in Tufted Duck (see Fig. 3) and slightly broader than would be typical of Greater Scaup. The black is substantially broader than Lesser Scaup which is normally resticted to the nail (see Figs 8 and 9 below).

Based on its broad and heavy bill, Toochin speculates that this individual might be a hybrid with Greater rather than Lesser Scaup. Indeed he states that "mixed trait birds seen occasionally in North America are usually taken to be Tufted x Greater Scaup, and most of these birds are probably true vagrants." He attributes this frequency to overlapping breeding ranges in Siberia and the Kamchatka Peninsula as well as in Iceland.

Other literature suggests that Tufted Duck x Greater Scaup hybrids are strongly reminiscent of Lesser Scaup and pose significant identification problems (Harris et al 1989; Randler 2001). To my mind, the fact that the Massapequa Lake bird was quite obvious amongst the Lesser Scaups argues against this specific combination. Could this be a more complex hybrid (e.g. Tufted x Scaup backcrossed to tufted again)!? This seems unlikely. Or could it reflect individual variations in hybrids? I tend to favor the latter. One trait of hybrids is that tend to be less stereotyped than 'true breeds'. In other words, there is more individual variation.  I wonder if chromosomal imprinting or other epigenetic effects might mean that the sex of the parental species also influences the outcome! Yikes!

I'd be interested to know if there is any way to narrow down which of the two scaups might be involved, that is without turning to genetic analysis.
 

Figs 8 and 9. Two views of male Lesser Scaup. Notice the dense vermiculations on the scapulars and back and shadowing of even finer vermiculations on the flanks. The bill is all blue without a pale band at the tip and the black is confined to the nail of the bill. Photos copyright of Angus Wilson.

Fig. 10. From behind the back could look very dark and similar to a full-blooded Tufted Duck. Unfortunately the Massapequa bird did not raise its wings during my observations, so I could not get any detail on the extent of the wing stripe. I would imagine that a Tufted x Greater Scaup might show a more extensive white wing stripe than a Tufted x Lesser Scaup, but have no confirmation of this. Photo copyright of Angus Wilson.

Andrew Middleton's web site includes a image of a similar looking drake Aythya hybrid (tufted x scaup?) photographed by Phil Vines in the Lea Valley, NE London, UK on on 4 Feb 2000.

Paul Barrows has a shot of a more Lesser Scaup-like bird from the Chew Valley, UK.

Another (even more) odd pseudo-Tufted Duck photographed by Matt Hysell at Grosse Ile, Michgan in February 2000

Useful literature

• Harris, A., Tucker, L and Vinicombe, K. (1989) The MacMillan Field Guide to Bird Identification. MacMillan Press, London.
• Mullarney, K., Svensson, L., Zetterstrom, D and Grant, P. J. (1999) Collins Bird Guide. HarperCollins, London.
• Randler, C. (2001) Field identification of hybrid waterfowl - Aythya. Alula 4: 148-156.
• Toochin, M. (1998) Possible anywhere: Tufted Duck Birding 30: 370-383.

Fig. 11. "You looking at me?" The hybrid is third from the right. Photo copyright of Angus Wilson