Rufous vs Allen’s -Addendum II

For readers in need of a basic primer on the Rufous/Allen’s ID issues, see Sheri Williamson’s post from Life, Birds, and Everything:

http://fieldguidetohummingbirds.wordpress.com/2010/09/06/rufous-vs-allens/

More interesting notes from Sheri on the Guilford, CT female, who kindly took the time to add the following:

Not only do molt patterns in other families not translate well to hummingbirds, but even generalizing from one hummingbird species to another in the same genus can lead you down the wrong track!

Like most highly migratory northern hummingbirds, Rufous normally undergo the most important parts of the molt (flight feathers and gorget) in winter. My first-hand experience with overwintering Rufous is limited, but the BNA account indicates that primary molt takes place mainly from late December through March, with females running 10+ days behind males. (Calder didn’t distinguish between age classes, but juveniles often average later onset and completion of primary molt than same-sex adults.) For a juvenile female, primary molt at P6 inmid-November (more than halfway along) would be ~8 weeks down the early side of the bell curve for Rufous, though apparently consistent with our limited understanding of molt in Allen’s.

Outlier characteristics often catch our attention, but attaching too much importance to them too often results in unproductive detours. As an extreme example, focusing solely on this bird’s primary molt would make HY Anna’s and Costa’s, both of which replace primaries mainly from early summer through late fall, stronger candidates than Rufous.

The diagnostic “pinched” tip of R2 is subtle, but it would be extremely unusual to find on a juvenile female and unusual *not* to find on an adult female or juvenile male. Here’s a new addition to my Flickr gallery that illustrates this difference: http://www.flickr.com/photos/tzunun/6385547925/in/set-72157619893017097/

Had R2 not been visible in any of the photos of the CT bird, the contrast in the gorget feathers would still have suggested a juvenile female, though with less confidence.

Within the “bee” hummingbird clade that most Americans and Canadians are familiar with, juvenile females are typically most “generic” in feather shape and pattern, while juvenile males and adult females tend to be more similar to each other than either are to juvenile females. This is one reason that I encourage birders to familiarize themselves with the broader aging and sexing criteria for hummingbirds before taking on the more challenging species.

If you know of any local/regional organizations that might be interested in a workshop on hummingbird identification and natural history, I’d be delighted to hear from them.

 Good birding,

 Sheri

 

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