Loading ...
Sorry, an error occurred while loading the content.

Re: [CALBIRDS] Island Scrub-Jay movements question

Expand Messages
  • Jeff Davis
    Dear Nathan -- Santa Rosa and Anacapa each are about 5 miles from Santa Cruz. As far as I know no Island Scrub-Jay has ever made it to either of these nearest
    Message 1 of 4 , Sep 30, 2002
    • 0 Attachment
      Dear Nathan --

      Santa Rosa and Anacapa each are about 5 miles from Santa Cruz. As
      far as I know no Island Scrub-Jay has ever made it to either of these
      nearest islands in modern times. And in fact the jay was thought not
      to have ever flown over water to get to Santa Cruz itself. Rather,
      it may have colonized during the northern Channel Islands peninsular
      stage of the Pleistocene (see CONDOR 74:295-315). Likewise there are
      no records of Western Scrub-Jay on any of the Channel Islands (~11
      miles from mainland to Anacapa) or the Farallon Islands (~25 miles
      from mainland to Southeast Farallon).

      Jeff Davis
      Fresno, CA

      At 15:41 +0000 10/1/02, Nathan Hentze wrote:
      >Up in the Pac. NW we've been experiencing a steady Western Scrub-Jay
      >northward expansion in recent years. I was wondering how much of a
      >barrier water is to scrub jays, and whether one would be likely to
      >island hop, or fly directly across one of the straits to reach
      >Vancouver Island. This led me to consider the Island Scrub-Jay, so I
      >am asking if an Island Scrub has ever been recorded on any of the
      >other Channel islands (ie., Anacapa, Santa Rosa), and what the
      >distance involved between Santa Cruz Island and the closest other
      >islands would be. Thanks very much for any answers regarding the
      >Island Scrub, or if anyone knows if water is at all a major barrier
      >to Westerns.

      --
    • Nathan Hentze
      Hello California birders, Up in the Pac. NW we ve been experiencing a steady Western Scrub-Jay northward expansion in recent years. I was wondering how much
      Message 2 of 4 , Oct 1, 2002
      • 0 Attachment
        Hello California birders,

        Up in the Pac. NW we've been experiencing a steady Western Scrub-Jay
        northward expansion in recent years. I was wondering how much of a
        barrier water is to scrub jays, and whether one would be likely to
        island hop, or fly directly across one of the straits to reach
        Vancouver Island. This led me to consider the Island Scrub-Jay, so I
        am asking if an Island Scrub has ever been recorded on any of the
        other Channel islands (ie., Anacapa, Santa Rosa), and what the
        distance involved between Santa Cruz Island and the closest other
        islands would be. Thanks very much for any answers regarding the
        Island Scrub, or if anyone knows if water is at all a major barrier
        to Westerns.

        You can reply off list if you want, to
        w_tanager@ hotmail.com

        Nathan Hentze,
        Cumberland, BC, Canada
      • Jeff Davis
        The paper I cited earlier was an old one. Paul is right about the more current view of Pleistocene bathymetry. And apparently there was a record of Western
        Message 3 of 4 , Oct 1, 2002
        • 0 Attachment
          The paper I cited earlier was an old one. Paul is right about the
          more current view of Pleistocene bathymetry. And apparently there
          was a record of Western Scrub-Jay from the Farallones. But Ned
          Johnson, in the same 1972 paper I cited before, considered the bird
          to be human assisted. Pyle and Henderson (WESTERN BIRDS 22:41-84) do
          not even mention it in their 1991 summary of occurrence patterns of
          SE Farallon birds. In a nice overview in BIRDING (29:476-485; 1997),
          Atwood and Collins suggest the most plausible explanation for the
          presence of the jay on Santa Cruz Island is overwater flight. During
          the late Pleistocene this distance would have been as little as 4
          miles. But, apparently, available molecular data cannot be used to
          determine time of divergence with other Aphelocoma jays. Therefore
          the approximate time of its arrival on the island is not known. The
          origin of slender salamanders and a night lizard on some of the
          islands is mysterious. Schoenherr, Feldmeth, and Emerson (Natural
          History of the Islands of California, UC Press, 1999) suggest they
          may have arrived by vacariant transport, associated with plate
          tectonics. In the Miocene the northern islands may have been
          connected to the mainland much farther south, but slid northward
          along fault systems to their present location. Although overwater
          flight during the Pleistocene seems a more likely hypothesis for the
          jay's island origin than vacariance during the Miocene, perhaps the
          latter cannot be ruled out.

          Jeff Davis
          Fresno, CA


          At 00:21 -0700 10/2/02, Paul Keller wrote:
          >My take on the Island Scrub-Jay is different than that of Jeff Davis, though
          >not being any expert I acknowledge that Jeff's account may be more accurate
          >than mine. Anyway, here goes.
          >Minimum sea level during the Ice Age was about 120m lower than today's
          >which, given modern bathymetric data, is insufficient to expose a land
          >connection to any of the Channel Is. It would, however, result in Anacapa,
          >Santa Cruz I., Santa Rosa I. And San Miguel I. being connected into one
          >large island called Santa Rosae which lay only a few kilometers from the
          >mainland. Therefore ancestral scrub jays must have crossed at least such a
          >water barrier. Perhaps a warm dry spell between the melting of the ice
          >about 12000 years ago (and the restoration of current sea level) and today
          >exterminated the jays from all the northern Channel Is. except Santa Cruz I.
          >I thought that there was indeed a record of a Western Scrub-jay on the
          >Farralon Is. Is there any expert with access to such records that can
          >clarify this issue? Jeff, if you are such an expert, my apologies.
          >My hope is that there's continued discussion about the Island-Scrub-Jay
          >distribution question, a question that has piqued my curiosity for some
          >time.

          --
        • Paul Keller
          On 02/10/01 08:41 AM, Nathan Hentze wrote: My take on the Island Scrub-Jay is different than that of Jeff Davis, though not being any
          Message 4 of 4 , Oct 2, 2002
          • 0 Attachment
            On 02/10/01 08:41 AM, "Nathan Hentze" <w_tanager@...> wrote:

            My take on the Island Scrub-Jay is different than that of Jeff Davis, though
            not being any expert I acknowledge that Jeff's account may be more accurate
            than mine. Anyway, here goes.
            Minimum sea level during the Ice Age was about 120m lower than today's
            which, given modern bathymetric data, is insufficient to expose a land
            connection to any of the Channel Is. It would, however, result in Anacapa,
            Santa Cruz I., Santa Rosa I. And San Miguel I. being connected into one
            large island called Santa Rosae which lay only a few kilometers from the
            mainland. Therefore ancestral scrub jays must have crossed at least such a
            water barrier. Perhaps a warm dry spell between the melting of the ice
            about 12000 years ago (and the restoration of current sea level) and today
            exterminated the jays from all the northern Channel Is. except Santa Cruz I.
            I thought that there was indeed a record of a Western Scrub-jay on the
            Farralon Is. Is there any expert with access to such records that can
            clarify this issue? Jeff, if you are such an expert, my apologies.
            My hope is that there's continued discussion about the Island-Scrub-Jay
            distribution question, a question that has piqued my curiosity for some
            time. -- Paul Keller, Goleta SBA

            > Hello California birders,
            >
            > Up in the Pac. NW we've been experiencing a steady Western Scrub-Jay
            > northward expansion in recent years. I was wondering how much of a
            > barrier water is to scrub jays, and whether one would be likely to
            > island hop, or fly directly across one of the straits to reach
            > Vancouver Island. This led me to consider the Island Scrub-Jay, so I
            > am asking if an Island Scrub has ever been recorded on any of the
            > other Channel islands (ie., Anacapa, Santa Rosa), and what the
            > distance involved between Santa Cruz Island and the closest other
            > islands would be. Thanks very much for any answers regarding the
            > Island Scrub, or if anyone knows if water is at all a major barrier
            > to Westerns.
            >
            > You can reply off list if you want, to
            > w_tanager@ hotmail.com
            >
            > Nathan Hentze,
            > Cumberland, BC, Canada
            >
            >
            >
            > Unsubscribe: mailto:CALBIRDS-unsubscribe@yahoogroups.com
            > Website: http://groups.yahoo.com/group/CALBIRDS
            > Listowners: mailto:CALBIRDS-owner@yahoogroups.com
            >
            > For vacation suspension of mail go to the website. Click on Edit My Membership
            > and set your mail option to No Email. Or, send a blank email to these
            > addresses:
            > Turn off email delivery: mailto:CALBIRDS-nomail@yahoogroups.com
            > Resume email delivery: mailto:CALBIRDS-normal@yahoogroups.com
            >
            >
            >
            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >
            >
          Your message has been successfully submitted and would be delivered to recipients shortly.