Gary,
Someone has probably already sent you this link but just in case check the
section under "Feeding Behavior."

http://en.wikipedia.org/wiki/Crossbill

On Mon, Mar 23, 2015 at 10:21 PM, lsr at ramoslink.info <lsr at ramoslink.info>
wrote:

> Garuy,
>
> According to BNA:
> Bill distinctive, with mandibles curved and crossing at tip. Lower
> mandible crosses to right as often as to left.
>
>
> Scott Ramos
> Seattle
>
>
> ------------------------------
> *From*: "Gary Bletsch" <garybletsch at yahoo.com>
> *Sent*: Monday, March 23, 2015 9:00 PM
> *To*: "Tweeters Tweeters" <tweeters at u.washington.edu>
> *Subject*: [Tweeters] crossbill question
>
> Dear Tweeters,
>
> It occurred to me today that I did not know the direction of the curvature
> of the bill of a crossbill. I looked at some pictures on the Internet, and
> saw some variation. With these images, I figured there might be some photos
> that had been reversed according to the photographer's whim, perhaps.
>
> The pictures in my copy of Big Sibley show the top mandible going to the
> bird's right, in both of our species of crossbills.
>
> The pictures in Lars Jonsson's *Birds of Europe with North Africa and the
> Middle East *appear to show the top mandible going to the left on a male
> Red Crossbill, but the top mandible going to the right on the female. This
> book shows a male Parrot Crossbill with the top mandible going to the
> right, with the female's top mandible going left. Then it shows the
> White-winged Crossbill female's top mandible going right. I couldn't tell
> what Jonsson was showing on the male White-wing, because the bird is
> depicted with bill open, attacking a cone.
>
> I had always assumed that crossbills had the same sort of chirality as
> that seen in the various species of flatfishes, where the "handedness" was
> always the same in a given species, barring rare mutations.
>
> How does this work in crossbills?
>
> Yours truly,
>
> Gary Bletsch
>
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>
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