caurinus hendersoni griseus

Transcription

1 Plate by Andy Birch

2 caurinus hendersoni griseus

3 Acknowledgements to the dowitcher and shorebird gurus Richard Crossley Julian Hough Jean Iron Alvaro Jaramillo Frank Pitelka Kevin Karlson Ken Kaufmann Michael O Brien Ron Pittaway Claudia Wilds

4 What is Gestalt or Jizz? How Can Birders use It? Ruff Sharptailed Sandpiper Pectoral Sandpiper Buff-breasted Sandpiper Upland Sandpiper

5 Gestalt ~ Anthropomorphizing field marks Humans have an innate ability to recognize each other

6 Who are these people?

7 Can gestalt be used as a field mark? Drawbacks no single gestalt field mark is conclusive gestalt field marks are hard to quantify gestalt field marks can vary Advantages when gestalt field marks are used together, one has a powerful tool for field ID

8 CAVEAT No single field mark is fail proof Holistic field identification is emphasized

9 OUTLINE FOR FIELD IDENTIFICATION IMPORTANCE OF GESTALT STRUCTURE ALTERNATE PLUMAGE BASIC PLUMAGE JUVENAL PLUMAGE DISCUSSIONS

10 STRUCTURE = GESTALT = GENERAL IMPRESSION Gestalt = conservative field mark Gestalt birding is not meant to replace looking at details They should complement each other

11 Semipalmated Sandpiper Western Sandpiper

12 DOWITCHERS gestalt

13 Long-billed Dowitcher Short-billed Dowitcher

14 Sep 4, 2004 Brazoria, TX LB Dow

15 Aug 6, 2005 Bolivar, TX SB Dow

16 July 31, 2005, Bolivar, TX Left = LBDO; upper right = SHBDO

17 Aug 25, 2005 Bolivar, TX Top: L to R; LB, ShB, LB, Shb; BOTTOM: L to R, ShB, LB

18 LORAL ANGLE DIFFERENCES IN FACIAL IMPRESSION A B A Long-billed Dowitcher Short-billed Dowitcher 20 number C Long-billed Short-billed FIGURE 1. A and B show how loral angle is defined using Long-billed (A) and Short-billed (B) dowitchers as examples. C shows a histogram of loral angles determined from photographs of the two dowitcher species Loral Angle (degrees)

19 SUMMARY OF STRUCTURAL FIELD MARKS Long-billed Short-billed Legs longer shorter Supercilium straighter more arched Loral angle smaller larger Posterior more elongated less elongated Posterior shape attenuated less attenuated Bill longer, straighter shorter, more decurved at tip Primary proj. shorter longer

20 Aug 11, 2005 Bolivar, TX SB Dow

21 SB Dow

22 Figure 3. This first-year, presumably male Long-billed Dowitcher was photographed 7 Jan 2006 at Bolivar Flats, TX. Note that although the length of the bill is on the shorter end of the spectrum for Long-billed, it appears straighter than Short-billed. Note more acute loral angle, straighter supercilium, dark chest and sides, barred (rather than chevroned) flanks), and dark upperparts. Some juvenal scapulars are still present.

23 LB Dow

24 LB Dows

25 OTHER CONSERVATIVE FIELD MARKS TAIL PATTERN SB Dow LB Dow Cin-Ty Lee

26 TAIL PATTERN SCHEMATIC Short-billed Long-billed

27 2. ALTERNATE PLUMAGE Usually attained in full by mid- to late April (molt begins on wintering grounds) Southward migration occurs in alternate plumage Main molt takes place on wintering grounds But LBDO undergoes partial molt during migration Spring birds are in fresh alternate (or transitioning into alternate) Summer/fall birds are in worn alternate (except for 1 st summer birds)

28 A B Figure 9. A) Long-billed Dowitcher in fresh-alternate plumage at Anahuac National Wildlife Refuge, TX in mid-april Note the squared off white feather tips on the median and greater coverts. Note also the black-barred sides of the breast and the diagnostic white edges to the black bars (these will be worn away by mid summer). Note also that the primaries do not project beyond the longest tertial. In this bird, black stripes on tail feathers distinctly thicker than white stripes. B) Longbilled Dowitcher in fresh alternate plumage photographed in spring in Japan, showing small loral angle, short primary projection, and long and straight bill, barred sides. Squared off white feather tips give this bird an overall white-barred appearance from a distance. Photo A by Lee and B by Yamamoto.

29 caurinus griseus hendersoni

30 Long-billed Dowitcher Alternate Greater Covert Feathers A B C Short-billed Dowitcher D E F G C-T Lee Figure 7. Fresh (A, B) alternate greater covert feathers in Long-billed. Worn Long-billed covert in C. Variations in fresh covert feathers in Short-billed (D-F) along with worn covert feather (G).

31 LB Dows SB Dows

32 SB Dow LB Dow

33 Top Long-billed Dowitcher, Bottom Short-billed Dowitcher

34 Top: LBDO (early April, bolivar); bottom LBDO

35 July 31, 2005, Bolivar, TX Left = LBDO; upper right = SHBDO

36 Aug 25, 2005 Bolivar, TX Top: L to R; LB, ShB, LB, Shb; BOTTOM: L to R, ShB, LB

37 30 July 2006 Ventura, CA SHBDO

38 SUMMARY OF ALTERNATE PLUMAGE FIELD MARKS Long-billed Short-billed Covert feathers flat white tips V-shaped white tips Flanks vertical bars fringed white bars or spots

39 2. BASIC PLUMAGE Usually attained in full by early September (although vestiges of juvenal plumage persist well into fall) Beware of first summer birds

40 Short-billed Long-billed

41 Short-billed Dowitcher Aug 11, 2004 San Diego, CA Pale, contrasting throat Scalloped/spotted sides which are lighter than neck

42 Pale chin, but less contrasting Barred sides which are same color as neck LB Dow

43 Short-billed Dowitcher, Wexford, Lady's Island 8th July 2004 Tom Shevlin Short-Billed Dowitcher, Azores, Cabo da Praia 14/12/03 Martin Oomen SB Dows - vagrants in Europe

44 19 Nov, 2005 Bolivar, TX 23 Nov 2006, Pelican Island, TX Ted Eubanks Long-billed Dowitcher LBDOs

45 Aug, 2005 Bolivar, TX SB Dow

46 LB Dows

47 Short-billed Dowitchers

48 3. JUVENAL PLUMAGE Short-billed Long-billed

49 Long-billed Dowitcher, Cornwall, Drift Res. 25/09/05 Andy Cook Long-billed Dowitcher, Cornwall, Drift reservoir 23 Sept 2005 Mike Barker Canon 20D f5.6

50 Sep 4, 2005, Bolivar, TX ShbDo