Date: 11/14/17 8:18 am
From: JOS GRZYBOWSKI <j_grzybowski...>
Subject: Red Crossbills this winter
Hello,   There appears to be an irruption of Red Crossbills occurring this year in North America.  There is already a scatter of records for Oklahoma.  There have been recent evaluations of Red Crossbill taxonomy that suggest up to 7 types that may represent individual species.  One type has already been officially delineated as such in the recent (2017) North American Checklist update.   Birds of each type wander together, so can maintain reproductive isolation by type.  The different types show a range of variation in bill structure for specializing on particular cone-producing species; however, the best way to distinguish types is from recordings of call.

   From the Cornell Lab  "Identifying the various flight call types (see http://ebird.org/content/ ebird/news/crossbills-of-north -america-species-and-red-cross bill-call-types/ ) typically requires audio recordings and spectrograms. Although a few birders perhaps can manage to separate the birds to type by ear only, these records generally should not meet the standards for validation, especially since we are still working out the distribution of the forms and since each irruption can have different compositions of the types."
   Even modest-quality recordings can be matched to type.  Some camera videos work.  Not sure on cell phones.  In previous years, the ranks of the Stillwater birders were identifying crossbills to type as possible.  If available, these can be sent to the Cornell lab for identification.
   So birders are encouraged to try to record any crossbills they encounter.  Pass the recording in.
CHEERS,                               JOE Grzybowski

 

 
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