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American Oystercatcher Hybrids

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  • wagtail1997
    This last week we received at the RBA reports of an American Oystercatcher type ..... Many of the American Oystercatchers that frequent southern California
    Message 1 of 1 , May 1, 2002
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      This last week we received at the RBA reports of an American
      Oystercatcher "type"..... Many of the American Oystercatchers that
      frequent southern California are hybrids with Black Oystercatchers.
      Jehls in 1985 came up with a scoring system for such individuals...and
      it was updated and published in an issue of Western Birds. I carry
      that chart (photoreduced) in my Sibley book.

      Stan Walens sent me a text file he has of the scoring system, and I
      repeat it below. If you have space in your field books, it might be a
      good idea to paste this in your book.

      Joel Weintraub, Dana Point, CA

      A score of 0 to 9 is characteristic of Black Oystercatchers, from 10
      to 29 to be hybrids, and from 30 to 38 to be American Oystercatchers.

      Upper Tail Coverts
      Black................................ 0
      Black, a few white mottling......... 1
      Nearly equally black and white... 2
      White, a few black mottlings........ 3
      White.............................. 4

      Tail
      Black........................................ 0
      Mainly black, trace of white at base of vanes... 1
      Basal quarter of rectrices white... 2
      Basal third of rectrices white..... 3
      Basal half of rectrices white...... 4

      Chest
      Black with black chest band extending smoothly onto midbelly 0
      Black chest band extending onto upper third of belly......... 1
      Black chest band extending onto upper quarter of belly........ 2
      Black chest band bordered by ragged edge on upper breast...... 3
      Black chest band sharply delimited from white of upper chest 4

      Belly
      Blackish.................................... 0
      Blackish, with traces of white on a few feathers.....1
      Blackish, white area around crissum ................. 2
      3/4 black, 1/4 white...................... 3
      Nearly equal black and white........... 4
      3/4 white, 1/4 black......................... 5
      Entirely white............................... 6

      Undertail coverts
      Entirely black 0
      Mainly black with slight white mottling 1
      Nearly equally black and white 2
      Mainly white........................ 3
      Entirely white.............................. 4

      Thighs
      Entirely black.................................... 0
      Black with grayish underdown, NOT noticeable externally (skin).. 1
      Puffs of grayish down noticeable.... 2
      Mainly white...................................... 3
      Entirely white................................... 4

      Greater Secondary Coverts (width of white edging in folded wing)
      White lacking.................................. 0
      Less than 2 mm................................ 1
      2-5 mm............................................ 2
      6-15 mm........................................... 3
      More than 15 mm........................... 4

      Extent of white wing stripe
      Lacking............................................. 0
      White markings confined to inner half of
      secondaries........................ 1
      White markings extend to outer secondaries but not to primaries....
      2
      White present on some or all of inner five
      primaries................... 3
      White present on a least one of primaries
      6-10............................. 4

      Underwing Coverts
      Entirely black.............................. 0
      Mainly black, some white mottling.. 1
      Nearly equally black and white....... 2
      Mainly white...................................... 3
      White................................................ 4

      Axillars
      Black............................................... 0
      Mainly black, some white mottling... 1
      Nearly equally black and white........ 2
      Mainly white...................................... 3
      White................................................ 4
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