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Swainson's Hawks

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  • The Jorgensens
    March 20,2007, between ~0900 and 0945, 1365 Swainson s Hawks were counted as they left their roost near our Borrego Valley hawkwatch, Borrego Springs, Ca. site
    Message 1 of 5 , Mar 21, 2007
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      March 20,2007, between ~0900 and 0945, 1365 Swainson's Hawks were counted as they left their roost near our Borrego Valley hawkwatch, Borrego Springs, Ca. site on DiGiorgio Rd. All of them had roosted in the valley. It was all the more dramatic because they kettled up together in several subgroups and were visible at one time as they flew northwest.

      Interestingly, this single flock exceeds the total breeding population in California. Whether they come from central Mexico, Argentina or elsewhere is a mystery. Their exact destination is also unknown, but necessarily includes areas outside California. Telemetry data of nesting central California birds from the 1990s was revealing but of a small sample size.

      Since staring the hawk watch here in 2003, we have had three similarly large groups and, surprisingly, have not found a report of more than a few birds anywhere on their western U.S. route (excluding Texas) north of Veracruz Mexico. In fact, we do not recall any reports in California, other than here in Borrego Springs and Imperial County, of more than 60 individuals in the last 7 years.

      Incidentally, our highest annual count was 5200 Swainson's in Spring 2004.

      Since Swainson's only average about 100 miles per day, this large group likely roosted last night in Riverside, San Bernardino or Los Angeles County. Birders should be on the lookout for large migrating groups especially from mid March to mid April, and again in late September and October.

      Paul Jorgensen
      Borrego Springs, Ca.
      92004

      [Non-text portions of this message have been removed]
    • Deren Ross
      Hello Paul, Thanks for the report of this timely, exciting and amazing report. A few of us are monitoring the hawk migration along the west slope of the
      Message 2 of 5 , Mar 21, 2007
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        Hello Paul,

        Thanks for the report of this timely, exciting and amazing report. A
        few of us are monitoring the hawk migration along the west slope of
        the Sierra....near Auburn (American River Watershed). We'll be out
        tomorrow and Friday. We'll certainly keep our eyes peeled for
        Swainson's.

        Thanks again,
        Deren Ross
        Auburn, Ca


        --- In CALBIRDS@yahoogroups.com, "The Jorgensens" <jorgy@...> wrote:
        >
        > March 20,2007, between ~0900 and 0945, 1365 Swainson's Hawks were
        counted as they left their roost near our Borrego Valley hawkwatch,
        Borrego Springs, Ca. site on DiGiorgio Rd. All of them had roosted
        in the valley. It was all the more dramatic because they kettled up
        together in several subgroups and were visible at one time as they
        flew northwest.
        >
        > Interestingly, this single flock exceeds the total breeding
        population in California. Whether they come from central Mexico,
        Argentina or elsewhere is a mystery. Their exact destination is also
        unknown, but necessarily includes areas outside California.
        Telemetry data of nesting central California birds from the 1990s
        was revealing but of a small sample size.
        >
        > Since staring the hawk watch here in 2003, we have had three
        similarly large groups and, surprisingly, have not found a report of
        more than a few birds anywhere on their western U.S. route
        (excluding Texas) north of Veracruz Mexico. In fact, we do not
        recall any reports in California, other than here in Borrego Springs
        and Imperial County, of more than 60 individuals in the last 7 years.
        >
        > Incidentally, our highest annual count was 5200 Swainson's in
        Spring 2004.
        >
        > Since Swainson's only average about 100 miles per day, this large
        group likely roosted last night in Riverside, San Bernardino or Los
        Angeles County. Birders should be on the lookout for large migrating
        groups especially from mid March to mid April, and again in late
        September and October.
        >
        > Paul Jorgensen
        > Borrego Springs, Ca.
        > 92004
        >
        > [Non-text portions of this message have been removed]
        >
      • Nick & Mary Freeman
        Hi Paul I lead a trip to the Owens Valley in the Eastern Sierras every April where in the Chalfant Valley, we visit a few of the ranches with ag fields. There
        Message 3 of 5 , Mar 21, 2007
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          Hi Paul

          I lead a trip to the Owens Valley in the Eastern Sierras every April
          where in the Chalfant Valley, we visit a few of the ranches with ag
          fields. There have been a few times where we've encountered over two
          dozen Swainson's Hawks.

          In April of 2007 at this location, we encountered a Swainson's in a
          flight display over another Swainson's perched on a telephone pole.
          We noticed the displaying bird had a 5" antenna sticking out from its
          back. I contacted Pete Bloom and I received a discussion by Dick
          Anderson as follows:

          During the last several years the CDFG has attached satellite
          transmitters to about 10 SWHAs in the Owen's Valley. The purpose was
          to understand late summer, early spring and migrational movements.
          This has been done in the Central Valley of CA also. The findings are
          that the Owen's Valley SWHAs migrate to Argentina with most of the
          North American SWHAs, but the majority of the Central Valley SWHAs
          migrate to Mexico for the winter. There are currently two active
          transmitters still on SWHAs in the Owen's Valley. You must have seen
          one of them.

          I thought I'd add to your discussion of your previous posting
          touching on the subject of telemetry data. I hope to encounter
          another hawk with an antenna pack on its back this coming April.
          Also, yesterday I received an email from a birder in Santa Clarita
          Valley where she had 20 Swainson's Hawks land on her property. Nick
          and I saw about 20 hawks kettling above East Los Angeles one February
          day 11 years ago. And finally, I recall Dustin Alcala some years
          back found a flock that roosted overnight at Hansen Dam which is
          located in the San Fernando Valley.

          Phenomenal reports from Anza Borrego!

          Mary Freeman
          Glendale, CA



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        • The Jorgensens
          A flock of approximately 100 SWAINSON S HAWKS were seen at 5:50 pm April 8 in Diamond Bar By Grace Clark. At that hour and flying so low, they were likely
          Message 4 of 5 , Apr 9, 2007
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            A flock of approximately 100 SWAINSON'S HAWKS were seen at 5:50 pm April 8 in Diamond Bar By Grace Clark. At that hour and flying so low, they were likely coming into an overnight roost. The location is approximately 2 miles north of the intersection of Grand Ave and the 57 freeway, just NW of the 57. Grace thought they might be seeking trees just north of the residential area.

            Please email me if you have any related sightings, such as possible further information about this or any roost site, or reports of other large flocks anywhere in California, not previously reported on Calbirds.

            Our total to date for Swainson's passing thru Borrego Springs Ca. this Spring is 2386.

            Paul Jorgensen
            Borrego Springs Ca 92004

            [Non-text portions of this message have been removed]
          • sam johnson
            Thanks to Al Knoll for his post. At 9:00 A.M. this morning there were still appx 40 Swainson s still in the field on Chiles Rd., quite a sight. By 11:30 A.M.
            Message 5 of 5 , Aug 9, 2007
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              Thanks to Al Knoll for his post. At 9:00 A.M. this morning there were still appx 40
              Swainson's still in the field on Chiles Rd., quite a sight. By 11:30 A.M. a number of them
              had moved over to the Vic Fazio Wildlife area which is just East of the first location.
              Sam Johnson




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