Saturday, April 2, 2011

Identifying Scaup

Separating Lessser from Greater Scaup is difficult. Take this male Lesser Scaup I saw during a late March visit to Faribault's Alexander Park.

The head shape is the main field mark.  Compare the head shapes in these first two photos.  The Lesser Scaup above has a slightly crested (or angled) head unlike the rounded head of the Greater Scaup in the next photo.  The bill shape is different too.  Lessers have smaller, straighter bills with less black visible at the bill tip.

Head color varies a bit between scaups, with Lessers with a purplish sheen, green in Greaters.  The general consensus is head color is not a reliable field mark. Greater Scaup tend to have brighter white sides than Lessers--but a quick look at these two photos indicates that this field mark is also unreliable.
If the scaup you are trying to identify flies, watch its wing stripe.  In the photo below, notice the white in the wing ends abruptly at the end of the secondary wing feathers.  The stripe in the primaries is dusky, not white.  That field mark signifies the Lesser Scaup.  The white in the wing stripe on a Greater Scaup continues into the primaries.  The head shape and the extent of the white wing stripe are both robust field marks.
Female scaup are more difficult to identify.  Again, look for head shape and wing bars (no help if she does not fly).  The female Lesser Scaup below has a slight angle to the back of her head.  Her bill is relatively short and straight.  Some female Greater Scaup show a white ear spot. If Lesser Scaup show this mark, it is less distinct than on a Greater Scaup. The female below completely lacks this secondary spot (as do many Greater Scaup). 

4 comments:

  1. How reliable a guide do you feel location is? I recently concluded that the scaup we were seeing locally were very likely to be Lessers because of this statement on All About Birds: "The Greater Scaup is found primarily along the seacoast and on large bodies of water."

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  2. Checkout the range maps in Sibley. The seacoast statement may be more or less true in the winter. Summer birds in MN are probably Lessers, as Greaters breed in the arctic. Greaters, however, should be common enough along the Central Flyway during migration.

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  3. Thanks for the guidelines, Dan. I was just out to the Minnesota River with Claudia Egelhoff--a fine birder, indeed. We were trying to distinguish scaup from ring-necked ducks. While lighting was not an issue, the birds were hunkered down while floating so their necks weren't extended. Distance was also a problem. Anything we might have used to help decipher? --Judy Chucker (P.S. I'm not a professor in real life)

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  4. I have a post in the pipe-line on Ring-necked Ducks. Ring-necks should show highly visible rings on their bills.The males should show obviously pale stripes behind their black breasts.

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