The SUBSPECIES and MIGRATION PATTERNS Of MERLINS
(Falco columbarius)
INTRODUCTION
I was asked, "Which subspecies of Merlin is found in the Stanford, California area?" As a consequence, I decided to do a literature survey on the topics of migration and subspecies of Merlins. I surveyed 22 bird books (mostly Eastern authors), and nine had no mention of subspecies. One book (Peterson's Western Birds) has the subspecies mislabeled.
The first conclusion from my Literature Survey is that the Black Merlin (F.c. suckleyi) is probably the most common in our area. The other two subspecies [Prairie (F.c. richardsonii) and Taiga (F.c. columbarius), the nominate species] are also possible. The second conclusion is that not a lot of effort has been spent documenting the subspecies of Merlin that winter in California.
One gets quite a different picture when one contacts Local Experts who have been viewing Merlins in this area for many years.
I have thought for some time that "Merlie" the Merlin, who has been coming back to a tree near our house for 10 years (as of 2001) is a Black Merlin (F.c. suckleyi). HOWEVER, after a more Careful Visual Study, I am NOW fairly cetain that he is a Taiga Merlin (F.c. columbarius).
LITERATURE REVIEW
Clark & Wheeler (1) mention three subspecies of Merlins: Taiga (F.c. columbarius), Prairie (F.c. richardsonii) and Black (F.c. suckleyi). "Taiga Merlins are darkest in the east and become gradually paler westward." "Prairie Merlins are paler and somewhat larger that other Merlins.." "Black Merlins are much darker than the other forms. Cheeks are mostly dark, and throat is streaked. Superciliary line, hind neck markings, and tail bands are faint or absent." Taiga Merlins "are fairly common along the ocean coasts (of the USA) in migration, where some remain in winter." Some Prairie Merlins "move in fall and winter south to northern Mexico, east to Minnesota, and west to Pacific Coast". Some Black Merlins "move as far as southern California and New Mexico in fall and winter".
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Wheeler & Clark (2), briefly mention some of the above information (it is basically a picture book).
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"Hawks in Flight" (3) mentions the prairie subspecies (F.c. richardsonii) that winters extensively in Oklahoma and the Texas panhandle; the Black Merlin (F.c. suckleyi) winters to southern California; and the nominate subspecies, F.c. columbarius, is slightly smaller, but is not always readily distinguished from the Black Merlin by color.
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In 1938, in the "Life Histories of North American Birds of Prey" (4), the author describes the Eastern pigeon hawk (F.c. columbarius), which winters "south to the Gulf States, the Caribbean region and northern South America"; the Black pigeon hawk (F.c. suckleyi) "breeds in British Columbia and winters only rarely as far south as northern California"; and Richardson's pigeon hawk (F.c. richardsonii) which winters "mainly east of the Rocky Mountains". The fourth race (supposed northwestern race), "bendirei, is to my mind only an intermediate between the darker and the lighter races, and is too near the eastern race to warrant recognition". Subsequently, other authors seem to have agreed (see Reference 13, below).
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Johnsgard (5) mentions three subspecies, columbarius, richardsonii, and suckleyi. He also mentions "Other Vernacular Names". Specifically; black Merlin (suckleyi), eastern pigeon hawk or taiga Merlin (columbarius), prairie Merlin or Richardson's pigeon hawk (richardsonii).
suckleyi (breeds in western Oregon north to Sitka, AK; occasionally wintering south to California and New Mexico)
richardsonii (breeds in southern Canada, Montana, South Dakota; winters south to northern Mexico)
columbarius (breeds widely in North America; wintering south to Peru)
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The "National Geographic Field Guide" (6) does a good job of describing the differences in the subspecies, but doesn't mention Taiga, Prairie, or Black.
suckleyi: very dark race of the Pacific Northwest; a few winter to southern California.
richardsonii: pale race that breeds in the northern Great Plains, winters to southern Great Plains, a few to the Great Basin and Pacific states.
columbarius: breeds in the taiga region (ed., moist subarctic forest that begins where the tundra ends), western columbarius average slightly paler than eastern.
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"The Sibley Guide to Birds (7) mentions Pacific (Black), Taiga, and Prairie. "Occasional Taiga birds from the east apparently resemble Black. Taiga population is widespread, wintering along both coasts. Prairie birds winter from Canada to Mexico, occasionally west to California. Black population winters along Pacific coast south to California, rarely east to New Mexico."
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All the Birds of North America" (8), mentions northwest coastal form (dark; eyebrow is obscured; tail bands narrow), plains form (pale body; mustache indistinct), and "typical", which is intermediate in color between the first two.
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"Peterson's Western Birds" (9) is really BAD. All the labels are wrong on the pictures for the three subspecies (see also, http://kaweahoaks.com/html/merlin.html). In the text, Peterson mentions the "prairie form" and the "coastal northwest form", but he doesn't link these terms to the subspecies names that are on the pictures.
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Arnold Small (10) is not very clear on the migration, but gives the nod to suckleyi (coastal British Columbia) for prevalence in California ("is occasionally recorded"), and richardsonii (central Canada) as "has also been observed".
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Kaufman (11) is no help on migration, and only mentions the races suckleyi and richardsonii with little information.
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The Suttons (12) only mention "the 'prairie merlin,' a pale race breeding in south central Canada and the northern prairie states."
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Grinnell and Miller (13) mention F.c. richardsonii as a "Winter visitant (to California). Perhaps fairly common, but verified records few." For F.c. suckleyi they say: "Vagrant or winter visitant from north. Apparently rare; at least, verified records are few." They don't mention F.c. columbarius. They discuss the subspecies, F.c. bendirei as: "Note: we were inclined to follow Swarth (Condor 37, 1935, 201) in his protest against the recognition of the race bendirei....". (See also Reference 4, above).
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The references (14-22) do NOT mention any Merlin subspecies.
REFERENCES
1. Hawks, William S. Clark & Brian K. Wheeler, Houghton Mifflin, 1987.
2. A Photographic Guide to North American Raptors, Brian K. Wheeler & William S. Clark, Academic Press, 1995.
3. Hawks in Flight, Pete Dunne, David Sibley & Clay Sutton, Houghton Mifflin, 1988.
4. Life Histories of North American Birds of Prey, Arthur C. Bent, Smithsonian, 1938 (Dover reprint 1961).
5. Hawks, Eagles, & Falcons of North America, Paul A. Johnsgard, Smithsonian, 1990.
6. Field Guide to the Birds of North America, 3rd Edition, National Geographic Society, 1999.
7. The Sibley Guide to Birds, David A. Sibley, 1st Edition, Knopf, 2000.
8. All the Birds of North America, American Bird Conservancy, Harper, 1997.
9. Peterson's Western Birds, Roger Torey Peterson, Houghton Mifflin, 1990.
10. California Birds, Arnold Small, Ibis Pub. Co., 1994
11. Lives of North American Birds, Kenn Kaufman, Houghton Mifflin, 1996
12. How to Spot Hawks & Eagles, Clay & Patricia T. Sutton, Chapters Publ., 1996.
13. The Distribution of the Birds of California, Joseph Grinnell and Alden H. Miller, Cooper Ornithological Club, 1944 (Reprinted by Artemisia Press, 1986).
14. The Audubon Society Field Guide to North American Birds (Western Region), Miklos D.F. Udvardy, Knopf,1977.
15. The Birder's Handbook, Paul R. Ehrlich, David S. Dobkin and Darryl Wheye, Simon and Schuster, 1988.
16. Stokes Field Guide to Birds (Western Region). Donald and Lillian Stokes, Little Brown, 1996.
17. Birds of North America, Kenn Kaufman, Houghton Mifflin, 2000.
18. Atlas of Bird Migration, Jonathan Elphick, Guest Editor, Random House, 1995.
19. Birds of North America, Golden Field Guides, 2001.
20. Birds of Northern California, David Fix and Andy Bezener, Lone Pine, 2000.
21. Birding in the American West, Kevin J. Zimmer, Cornell Univ. Press., 2000.
22. The Sibley Guide to Bird Life & Behavior, Knopf, 2001