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Thursday, January 3, 2013

"Eye-ringed Leaf Gleaners"

Hutton's Vireo (Vireo huttoni) 
photographed in Occidental on 3 January 2013

Hutton's Vireos look remarkably similar to Ruby-crowned Kinglets.  The differences are subtle, so it takes a close look to distinguish them.  In 1984, Rich Stallcup wrote a nice article about how to separate these two species; he titled it, "The Eye-ringed Leaf Gleaners."

There are several important field marks and behaviors.  When the birds are flitting around from branch to branch, the easiest field mark to see might be the wing pattern.  In Hutton's Vireos, the narrow yellow edges on the primary feathers run all the way up to the lower white wing bar.  In Ruby-crowned Kinglets, there is a distinct black patch between the yellow primary edges and the lower wing bar.  Here are two comparison photos (below).  Can you tell which is which?

[Hutton's Vireo in the first photo, Ruby-crowned Kinglet in the second.]

If you can see the bill, that's helpful, too.  In Hutton's Vireos the bill is thicker, has a distinct (although small) hook at the tip, and is paler below.  In Ruby-crowned Kinglets, the bill is thinner, pointed, and dark throughout. Compare the bills in the next two photos. 

[Hutton's Vireo in the first photo, Ruby-crowned Kinglet in the second.]  

An interesting side note: Vireos are related to shrikes, which also have hooked bills.  To appreciate this feature, here's a close-up of the first photo.

You can also check the legs and feet.  In Hutton's Vireo, the legs and feet are thick and blue-gray.  In Ruby-crowned Kinglets, the legs are very thin and black and the feet are slender and orange. 

[Ruby-crowned Kinglet in the first photo, Hutton's Vireo in the second.]

Their behavior can be different, too.  As Rich Stallcup says, "When foraging at ease, Ruby-crowned Kinglet is much more nervous acting and Hutton's Vireo slower and more deliberate."  Another useful description is that Hutton's Vireo has "slightly slower perch changes."

Hutton's Vireos are uncommon on Bodega Head, but look for them in oak woodlands, willow thickets, and Douglas-fir forests.  

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