Tale of two scoters

18 02 2009

What is a Seanetter to do when faced with a pair of black wings that are duck-ish in appearance?

Pair of wings found by Diana Gaumond of Cape Cod in March 2008.

Pair of wings found by Diana Gaumond of Cape Cod in March 2008.

For instance, in this first photo shown here, we see a pair of wings that are relatively short and broad (which is generally characteristic of a duck wing). Volunteer Diana Gaumond found this pair of wings and reported a wing chord of 22cm. Given the general appearance–uniformly dark with no colored speculum–and that relatively short wing chord, the hapless Seanetter could easily end up stuck between two scoters. Both the Black Scoter (wing chord 20-24cm) and the Surf Scoter (wing chord 20-25cm) seem to match, and without the head or feet, or anything else to use to differentiate, one could be forgiven for calling the bird “Unknown scoter” and moving on with one’s life. But no! One needn’t be content with such an i.d.!

Take a close look at the tips of the primaries (outermost feathers) in that first pair of wings. You can see that the very outermost primary is also the longest of all the primaries. This indicates that the bird is a Surf Scoter.

Compare that with the second photo, provided by Mary and Steve Gulrich. In this closeup, you may be able to appreciate that the outermost primary is actually shorter than the one beside it. This is characteristic of a Black Scoter.

Tip of wing found by Mary and Steve Gulrich of Cape Cod in February, 2009.

Tip of wing found by Mary and Steve Gulrich of Cape Cod in February, 2009.

While it is tough to tell from these photos, you will undoubtedly be able to see this difference in the field. So if you live in scoter country (and most of us do since their winter range is as far south as the northern Gulf of Mexico) don’t despair at the sight of a pair of black wings with a wing chord between 20 and 25. There is hope yet, Seanetters!

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2 responses

19 02 2009
Keith McCullough

Thank you so much for this and other posts that give useful identification tips. They prove very useful to me in the field.

19 02 2009
Jenette Kerr

Aha ! A great tip I not only can use but might actually remember ! Thanks, Sarah !

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