Lesser Scaup Aythya affinis
Bolsa Chica Wetland, California: 14 March 2005

Both Lesser and Greater Scaups winter in Southern California, and can be difficult to separate. Whilst this short note is not intended in any way to be an identification article the following points may be helpful to birders coming across male Lesser Scaups for the first time.

First, though, a compilation photo taken in Vancouver, May 2006 showing both a male Greater and a male Lesser Scaup.

Greater Scaup Aythya marila (top) and Lesser Scaup Aythya affinis

So, how easy is it to separate the two species? Male Lessers are fairly straightforward when seen well and when watched over a period long enough to make sure ALL the relevant features are noted - these include typically showing a purplish gloss to the head, a distinct peak to the crown behind the eye, and a small dark nail. The following pointers may help:

1. It is worth throwing away completely any notions that males are identifiable by head colouration alone - note Image 02 below where the foreground male shows a dark greenish tone to its head, whilst the bird in the background shows a supposedly “typical” purple gloss. Head tones change as the birds turn, or as the light changes.
2. The shape of the head can also change: though Lessers typically show a slimmer, taller head with a pointed rear crown, this can change radically when, for example, the bird becomes alert or is feeding when the head can become almost rounded.
3. Look for white secondaries contrasting with darker primaries on Lessers. Loafing birds preen regularly when the white flash can be very conspicuous.
4. Both species often occur in large, mixed flocks (when the larger size and heavier, longer bill of Greater becomes evident). Habitat choice is not a good ID determinant - especially as both will occur on coastal lakes and lagoons. However, whilst Greater is often found on inland freshwater lakes as well as at sea, Lessers do seem to occur less in maritime situations.
5. Male Greaters often look quite pale-backed from a distance: male Lessers tend to look a little darker - presumably as a result of the comparatively denser barring towards the rear of the mantle.

Image 01: Male Lesser Scaup, 14 March 2005

 

Image 02: Male Lesser Scaups (note head colour tones), 14 March 2005

 

Image 03: Male Lesser Scaup, 14 March 2005

 

Image 04: Male Lesser Scaup, 14 March 2005

 

Image 05: Male Lesser Scaups, 14 March 2005

 

Image 06: Male Lesser Scaup, 14 March 2005

 

Image 07: Female Lesser Scaup (with female Ruddy Duck behind), 14 March 2005

 

Image 08: Female Lesser Scaup, 14 March 2005

All photographs © Charlie Moores.