Thursday, August 16, 2012

Shorebird Identification: The Adult "short-winged" Peeps

The three species that will be discussed here are the Least, Semipalmated, and Western Sandpipers.  When in breeding plumage these three species are readily identifiable but when in nonbreeding plumage these species can be among the most challenging birds to identify.  Due to the differences in shape and size the Least is the most readily identifiable of the three.  In nonbreeding plumage the Semipalmated and Western look very similar.  But for those of us in the US we don't need to worry as much about the Semipalmated in nonbreeding plumage because they do not winter within the country.

Least Sandpiper

The plump, front-heavy body shape of the Least Sandpiper is important in it's identification at any season.  The yellow legs and short, slightly decurved bill can be used as a field mark throughout the year.  In breeding plumage, the adults are fairly evenly colored from the head and chest through the back to the tail.  Overall, it is the brightest plumaged peep.  The streaking on the chest is the densest on the Least Sandpiper as well.  

Adult Least Sandpiper.  Notice the overall dark plumage, fairly bright throughout, not concentrated in
specific areas like Western.  Bill:  short, slightly decurved, fine-tipped.  Shape:  large chested, plump overall

Nonbreeding Least Sandpiper:  Notice the yellow legs, slightly decurved bill, and plump body shape

Semipalmated vs. Western Sandpipers

By Shape:

The female Western Sandpipers can be identified easily in most situations due to their long, decurved bill.  However, the male Westerns have a shorter bill that overlaps the Semipalmated's bill length.  Even though the bill length isn't always the safest field mark the bill shape can still be useful.  The Western's bill is almost always more finely-tipped than the Semipalmated, which is more blunt-tipped.  The biggest difference in the shape is the overall body shape.  When these two species are seen together, the shape differences are obvious, when seen separately it can be difficult to discern.  If you look at a Semipalmated Sandpiper as a teeter-totter it would look even, neither side would be much heavier than the other.  If you did the same to a Western Sandpiper, one side would be weighed down.  So, in normal terms, the Western Sandpipers look front heavy and are very large chested.

Semipalmated Sandpiper
Breeding Semipalmated Sandpiper:  Bill:  short, blunt-tipped, Plumage:  mostly brown
overall, Shape:  Evenly distributed
To see the photographer's photostream go to:
http://www.flickr.com/photos/pancamo/5698339916/
Maçarico-rasteirinho (Calidris pusilla)
Nonbreeding Semipalmated Sandpiper:  Bill:  short, blunt-tipped, Plumage:  dark streaking
on sides of chest, but the streaking isn't messy, or down the sides at all
To see the photographer's photostream go to:
http://www.flickr.com/photos/cdtimm/5349850457/

By Plumage:

In breeding plumage these species are easy to identify due to the striking plumage of the Western.  The rufous in the crown, auriculars, and scapulars should do the trick when identifying this shorebird.  Semipalmateds are more evenly colored overall and are never as bright as Western Sandpipers.  

In nonbreeding plumage these two are quite difficult to identify.  If you are not comfortable identifying these species by shape there are a couple plumage characteristics to look for.  The most obvious is the messy streaking on the chest and sides of Western Sandpiper.  In some cases, Western will show some streaking or chevrons down the sides which Semipalmated don't show.  A less obvious characteristic to look for is the whiter chest of the Western.  The Semipalmated show dense streaking on the chest which causes the Semipalmated to look dark-chested.

western sandpiper
Breeding Western Sandpiper:  Plumage:  very brightly colored on the scapulars,
auriculars, and crown, note streaking/chevrons down the side, Bill:  long, decurved
To see the photographer's photostream go to:  
http://www.flickr.com/photos/seaotter/7125395311/ 

Nonbreeding Western Sandpiper:  Bill:  long, decurved, Plumage:  messy streaking on the chest, some streaking
down the sides (Semipalmated doesn't show this)
To see the other peep identification posts go to http://nuttybirder.blogspot.com/p/bird-identification-articles.html#.UC06Pt1lStw and scroll down.

-Eric

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