The SUBSPECIES and MIGRATION PATTERNS of the MERLIN
(Falco columbarius)
LOCAL EXPERT: BRIAN WALTON
My first conclusion from my Literature Survey was that the Black Merlin (F.c. suckleyi) is probably the most common subspecies of Merlin in the San Francisco Bay Area. The other two subspecies [Prairie (F.c. richardsonii) and Taiga (F.c. columbarius), the nominate species] are also possible. The second conclusion was that not a lot of time has been spent documenting the subspecies of Merlin that winter in California.
I then contacted a local expert, Brian Walton, who is Coordinator of the Santa Cruz Predatory Bird Research Group. His experience paints a different picture, as quoted below.
"These are my personal experiences. I have been observing merlins in California for over 30 years. I have possessed all three species and bred merlins in captivity. I have trapped some in the SF Bay area and lived in the Bay area for 25+ years.By far the most common merlin in the Bay area and California is the columbarius merlin. The next most common but decidedly rarer is the Richardson, and the rarest is the suckleyi. This is also true for North America. The columbarius can be found anywhere in California in the fall and winter. The Richardson is more common in the winter, and it is the species that nests in urban areas more commonly every year so there are increasing urban sightings although columbarius merlins still are more common in urban and non-urban California. The suckleyi merlin is a rare form that breeds in the coastal island strip of the Pacific Northwest and is akin to the Peale's peregrine. It is far more common in the coastal areas, but can be seen inland and we have received two rehab birds over the years from the Stockton/Los Banos area so in the Bay area at least you could see one most anywhere.
The columbarius merlins are quite variable. Just because a bird is dark does not make it a suckleyi. The size, weight, number of tail bars and degree of black pigment all come into play. Also plumage wear and moult can change the look of an individual bird significantly over the year. Richardson merlins are much more consistent, and they are very light often yellowish in appearance. The suckleyi are very dark, especially on the breast and the tail may appear black. Many people call dark columbarius birds suckleyi.
When these three species are observed at nests (which to me is the definitive way to observe differences between subspecies) then telling them apart is realistic. On migration, without the ability to tell size, weight, and origin it can be difficult to impossible to be accurate. I see the same thing with people trying to distinguish subspecies of peregrine falcons. Any light-colored anatum is called a tundra. Any dark-colored bird is called a Peale's.
I think it is great to try and differentiate. People just need to realize that when a bird is not in the typical plumage for a subspecies, if it is anywhere near an intermediate between two subspecies, it is not realistic to accurately describe the bird to subspecies. It is good to pay attention, and good to characterize the bird as columbarius-like or Richardson-like etc, but for accurate record keeping and if you really need to recognize the subspecies, at times it is impossible unless the bird is in the hand or at a nest.
Ten years of viewing Merlie is a great and unusual opportunity. They can live a lot longer so good luck. Few do of course, maybe yours will be a lucky one. Thanks for the contact."
Brian James Walton, Coordinator
Santa Cruz Predatory Bird Research Group
Long Marine Lab, University of California
Santa Cruz, CA 95060
(831) 459-2466 or 458-1237 messages
(831) 458-1237 or 459-3115 (FAX)