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Kings County Falcon re-visited

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  • erpfromca@aol.com
    Based on new information Steve and I have received, we now believe that the Kings Co. falcon IS a Gyrfalcon. In fairness to Steve, based on his initial
    Message 1 of 1 , Nov 28 3:37 PM
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      Based on new information Steve and I have received, we now believe that the
      Kings Co. falcon IS a Gyrfalcon. In fairness to Steve, based on his initial
      observations when he found this bird, he has felt all along that Gyr should not
      be ruled out.

      My main reason for thinking the bird was not pure Gyr was based on size.
      That estimate of size was from my 'impression' plus a rough re-sizing of the
      Peregrine photo and the Kings Falcon photo which suggested that it was
      'slightly' bigger than the Peregrine. Kevin Spencer took the photos and did a much
      more meticulous set of measurements. This showed a much larger difference in
      size than I recognized. He estimated the Peregrine at 15-16 inches and the other
      bird at 20-21 inches (from top of head to tip of tail). Kevin used the
      widths of the crossbars on the telephone poles as a 'ruler' to make this
      calculation. I contacted a former lineman who looked at the photos and, based on his
      experience said that the crossbars look like standard sized one and the widths
      are generally in the range of 4-4.5 inches. Steve took these measurements
      (using 4.25 inches) and re-measured the two birds. The Peregrine came out at
      15.5 inches and the other bird at 20.4 inches. A pdf has been placed in the
      Files section of CALBIRDS showing how this was done using the peregrine
      photographed five poles down.

      Published sources (Wheeler, NGS Guide, Petersen Guide) report the range of
      Peregrine length at 14-20 inches and the Gyrfalcon from 19-25 inches. Of
      course, these measurements are generally based on specimens measured from beak tip
      to tail tip. Therefore, one could add a bit to our top-of-head to tail
      measurements made from the photos. In any case, this info puts the Kings County
      falcon right into the proper size range for a Gyrfalcon.

      Additionally, Steve sent the photos to Brian Wheeler (co-author and
      illustrator for the Petersen Field Guide "Hawks" and author of "Raptors of Western
      North America") and below is his response:

      "This is a dark intermediate morph juvenile Gyrfalcon. Too dark on body and
      head for an intermediate or gray morph. I just finished painting four plates
      of Gyrfalcons (of 92 color plates) for a set of raptor field guides for
      Princeton University Press due out in 2011."

      We also got the following comment from Bud Anderson (Washington-state based
      director of the Falcon Research Group and a global falcon biologist)

      "Nice Gyr. I have no problem with a juv flying to CA. If it is a falconry
      bird, it will have jesses. And, to me, its just a standard, perfectly normal
      young Gyrfalcon. We see birds exactly like this most every year on the Skagit.
      Also too nice and pristine a plumage to have been in captivity."

      We have also heard from one falconer with experience with Sakers and various
      Gyr hybrids who also believes this bird looks like a perfectly good
      Gyrfalcon and also believes this is a wild bird. Comments from other falconers were
      all over the map: one said its a Saker, one said Gyr x Peregrine, another Gyr
      x ?, another Peregrine x Saker and one suggested Prairie x Peregrine!
      Unfortunately, none of this came with details about why any of the characters of
      this bird are inconsistent with it being a Gyr. Although I don't know one could
      ever completely rule out some kind of Gyr hybrid, in the absence of a single
      plumage character that is inconsistent with Gyr, Gyrfalcon should be the
      default. If it looks like a Gyr, is the size of a Gyr, flies like a Gyr, maybe it
      IS a Gyr.

      The only other characteristic of this bird that I didn't like for Gyr was
      the relatively 'slim' look. Not bulky and big bodied as nearly all Gyrs look in
      photos. Of course, one needs to realize that nearly all those photos are
      taken in cold to very cold conditions when a bird is likely to have its feathers
      fluffed up. This bird was sitting in Kings County with temps in the
      mid-sixties. It also possible that the bird is somewhat emaciated.

      Now that we're pretty sure this is a Gyrfalcon, the ugly issue of provenance
      comes to the fore. Is it wild or is it an escaped falconers bird? All we can
      say is that the bird had no jesses (nothing seen by Steve or myself perched
      or in flight), and no bands or anklets could be seen-legs obscured by
      feathers. Also, I see no evidence of the kind of feather wear that one often sees in
      birds kept in confined spaces. The bird flew away when I approached it, but
      then I wasn't holding any raw meat in my hand at the time (got to start
      carrying a baggie of raw hamburger from now on).

      On the other hand, a wild Gyrfalcon this far south in California is
      unprecedented (sort of like a Ross's Gull at the Salton Sea...?). Of the ten accepted
      CA records (plus the bird seen this year in Del Norte Co.), the southernmost
      records are birds from Yolo/Solano Counties. All other records are from the
      'far'' north (Del Norte, Siskiyou, Modoc, Humboldt and Shasta). This puts
      this bird over 200 miles south of the nearest prior accepted record. A long way,
      but then, not so long for a bird like a Gyrfalcon?

      Steve and I are going to gather more input and then put this into the
      capable hands of the CBRC (have fun guys--and gal...).

      In the meantime this bird could very well still be roaming around the area
      and we hope others will keep looking for it.

      Thanks to all who contributed comments and to all for your patience in
      wading through these LONG messages.

      Ed Pandolfino/Steve Summers

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