If there is still interest in this topic, folks might want to look at my photos of five Savannah Sparrow specimens from San Luis Obispo County, California:
http://gallery.me.com/lrbevier#100121. I photographed these while visiting the Royal Ontario Museum (ROM) in December 2007. The five birds include three individuals of migratory western Savannah Sparrows, a resident breeding bird from Morro Bay (alaudinus; these are called Belding’s in the Birding article), and a Large-billed (rostratus). I think one can see two things: (1) none of the specimens from San Luis Obispo County look anything like typical eastern birds; and (2) among the migratory western birds, the small, finely streaked coastal breeding birds from sw. British Columbia to extreme n. California (brooksi) are fairly distinctive, although perhaps not readily so in the field. The two other migratory western birds are similar to each other and nevadensis and/or anthinus. Would birders be motivated to learn something about the biogeography, migration, and wintering ranges of these birds if all continental populations were subsumed under one name? A paper by Jim Rising last year (Wilson Journal of Ornithology 121 [2]: 253-264, 2009), notably unmentioned in the Birding article, analyzed plumage pattern and coloration among Savannah Sparrows. Surprisingly, no specimens of these coastal Pacific Northwest birds were sampled. This makes me wonder if we aren’t susceptible to the pendulum swinging too far the other direction, lumping taxa with perhaps the same gaps in sampling on which some poorly defined subspecies were defined.
Moving the species boundary between Belding’s and Savannah Sparrows into San Luis Obispo County raises interesting questions. The Morro Bay bird in my photos was difficult to distinguish from beldingi specimens (s. Santa Barbara County south); so allying them with Belding’s is plausible. The same dark birds as found in Morro Bay also occur to the south at two river estuaries in w. Santa Barbara County (Santa Maria R. and Santa Ynez R.) but are disjunct by 60 miles of coastline and a major biogeographic break from the northernmost "true" belding in s. S.B. Co. To the north, similar birds to Morro Bay occur all the way to Humboldt Bay. This is the range of the subspecies alaudinus (= bryanti of older literature). Unlike the populations currently defined as beldingi from s. Santa Barbara County south, however, these northern birds are not as closely tied to saltmarsh, also nesting in the fog-belt grasslands along the coast. I think the break between southern Santa Barbara birds and the w. S.B. Co. birds included by Rising with beldingi is so far unexamined; also, the nature of the transition to the north of San Luis Obispo County to central Monterey County (and northward) remains poorly studied. I should point out that these nuances were noted by Grinnell and Miller (1944) decades ago.
No doubt many subspecies are erroneous or simply arbitrary subdivisions within a cline. But a serious attempt to properly quantify and rigorously define subspecies has been underway (see "Avian Subspecies" Ornithological Monograph no. 67, 2010). Some who have attempted to gauge the validity of subspecies suggest that as many as half might not be valid (e.g., Patten et al. in "Birds of the Salton Sea"). Nevertheless, disparagement of the junky subspecies in the empty half of the glass discounts the wonderful utility of the other half for evolutionary inquiry. Forgotten also, I think, is the role that these old names play as a link to the literature and the descriptive history of birds. Many of the nuances and exceptions to geographic patterns are there in those old papers but too often overlooked. Lastly, I think there has been an over-reliance on molecular genetic analyses, which often are based on even fewer samples with less regard to proper geographic sampling than some original descriptions of subspecies. Molecular markers hold great promise, but evolutionary inferences based on mitochondrial DNA, for example, have major limitations. The results are also misinterpreted with regard to what constitutes subspecies (e.g. and expectation of reciprocal monophyly when by definition there is gene flow between subspecies). One can spot genetic results that don’t make sense when the trees (cladograms) do a poor job of explaining the morphology or biogeography; the Birding article (and the paper upon which the genetic data are based, Zink et al., Condor 107: 21-28, 2005) seems a good example of this, with Ipswich and Large-billed Savannah Sparrows unresolved.
I’ll admit a bias, I really like the idea of Large-billed Savannah Sparrow as a species, but just as the lower limit of what constitutes a subspecies is problematic, so is the delimitation of some closely related species. Are the San Benito birds good species because they don’t nest in saltmarsh but share alleles and many morphological traits with the mainland birds? Nesting away from saltmarsh also occurs in at least one population of beldingi on the Todos Santos islands off Ensenada. This shift away from saltmarsh is also shown in the birds from w. Santa Barbara County north in California. What if rapid evolution or a short time in isolation means mtDNA is the wrong marker to reveal genetic differences of the Ipswich Sparrow, and we are misclassifying it as a subspecies? A paper published this year by Joseph Tobias et al. on delimitation of species would seem to be the perfect tool to analyze these questions. Those authors outline a system for quantifying and weighting characters that I think is a step forward (see Ibis 152: 724–746, 2010).
I agree with Alvaro that it would be great to come up with another way to communicate geographic variation without the typological connotations inherent in names. I’ve thought that a sort of shaded topographical map representing character changes across a geographic range would be effective. But the problem with naming clines or trying to represent them with gradations on a map is that the underlying data are likely to be just as inadequate and sparse as the data for some described subspecies. The practical effect would be graphs or names that mislead as much as outlining ranges. Another approach is that taken by David Sibley, where groups of populations are identified with geographic regions. I like this and it works well. Nevertheless, one loses the link to the underlying specimens and associated localities identified in the literature. The regional names can be nebulous, or misconstrued, too. I think we just have to accept that organisms are variable and remember to read the fine print. As an example, look at the marvelous plate by George Miksch Sutton in A. J. van Rossem’s paper on the Baja and northwest Mexican Belding’s and Large-billed Savannah Sparrows (
http://elibrary.unm.edu/sora/Condor/files/issues/v049n03/p0097-p0107.pdf). The diversity is there to see, and I don’t think the names really matter.
Louis Bevier
Fairfield, Maine
