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WebExtra Feature—supporting material for Birding articles that can be found only on the ABA website. When you come across this logo in Birding, visit these archive pages to view the extended article.
The Many Savannah Sparrows
November 2010 Birding
Photos by © James D. Rising
As we learned in the main print version of this article (Birding, November 2010, pp. 44–55), the coastal salt marshes of southern California and northwestern Mexico are a hotbed of diversity and speciation in the “species” currently classified as the Savannah Sparrow. Indeed, these marshes may be home to three species distinct from and separate from the main continental population of the Savannah Sparrow. Sparrow expert James D. Rising proposes to call these three species Belding's Sparrow, San Benito Sparrow, and Large-billed Sparrow.
Due to printing constraints, we were able to publish only a few photos of each of the distinctive candidate species from these salt marshes. In this WebExtra, however, we provide an extensive suite of images. Most are Rising's own photographs, taken in the course of field work in the 1980s and 1990s.
This 1947 map by the ornithologist A. J. van Rossem shows the distribution in northwestern Mexico of a complex of subspecies of the Savannah Sparrow.
This Belding's Sparrow is from Bahía San Quintin, on the west coast of Baja California, 30 March 1999. Note the dark coloration overall, along with the fairly large and long bill. These birds breedand are probably residentin salt marshes along the coast.
This Belding's Sparrow is from Guerrero Negro, Baja California Sur, 1 April 1999. Note the large bill. This bird's coloration is paler overall than Belding's Sparrows from farther north on the coast of Baja California and extending north to southern coastal California.
This is habitat for Belding's Sparrows at Guerrero Negro, Baja California Sur, 1 April 1999. The halophytic (salt-loving) vegetation here is dominated by plants in the genera Salicornia, Sueda, and Allenrolfea.
In this 25 April 1999 photo of a Belding's Sparrow, also from Guerrero Negro, note the dark breast markings, the large bill, and the thin median crown stripe.
This San Benito Sparrow was photographed on the Islas San Benito, 25 April 1999. Note the very large bill, the absence of yellow on the head, and the absence of a median crown stripe. These birds are not found in salt marshes, unlike most Belding's Sparrows. The San Benito Islands are “xeric” (dry) and probably lack freshwater.
This is a San Benito Sparrow, photographed 25 or 26 April 1999. The geographic range of the San Benito Sparrow is substantially more limited than that of the Large-billed and Belding's sparrows.
This San Benito Sparrow was photographed 26 April 1999. Note the large, conical bill.
This Belding's Sparrow at Laguna San Ignacio, Baja California Sur, was photographed in February in the mid-1980s. The sparrows are common there, but access to them is difficult.
This Belding's Sparrow is from Bahía Magdalena, Baja California Sur. The bill is long, but not particularly deep. Sparrows in this area are found both in salt marshes and in mangroves.
This Belding's Sparrow from Bahía San Quintin, Baja California, was photographed 30 March 1999. The Belding's Sparrow subspecies-group (treated as a full species by Rising) consists of multiple named subspecies. Rising believes the number of Belding's subspecies should be reduced to two.
This Belding's Sparrow is from Bahía San Quintin, Baja California, 30 March 1999. Like other sparrows of salt marshes (for example, the Seaside and Saltmarsh sparrows of eastern North America), its bill is notably longan adaptation for foraging on mud in Salicornia marshes.