The brackish and salt marshes of California are an important and globally threatened ecosystem. At this point, a century plus of “civilization” has filled, polluted or otherwise destroyed over 95% of the historical expanse of California’s coastal salt marshes. These estuaries and marshes are incredibly important. Biologically speaking, they are some of the most productive acres of habitat anywhere, hosting tremendous species diversity, and acting as vital nursery grounds for many ocean-dwelling species. They serve as feeding and breeding resources for a variety of species, some endangered like the California Least Tern, the Western Snowy Plover and the Light-footed population of Ridgway’s Rail. They also provide wintering or year-round habitat for a number of interesting bird species. The focus of this article is three such species: Belding’s (Savannah) Sparrow, Large-billed Savannah Sparrow and Nelson’s Sparrows.
Here in southern California, a visit to a coastal marsh like the Bolsa Chica Ecological Reserve in Orange County invariably produces a view of Belding’s Savannah Sparrows (Passerculus sandwichensis beldingii). They flit from perch-to-perch in the pickleweed (Salicornia), skitter between low bushes or perch on the fences briefly. Their reedy, squeaky songs can be heard across the marsh from nearly all points. So what makes them interesting? Well, the Savannah Sparrow complex is, taxonomically, a hotbed of genetic diversity and interesting local forms or populations. In the northeast, the Ipswich Sparrow (Passerculus sandwichensis princeps) is a globally-threatened subspecies noted for its size and overall pallor. The largest population of Savannah Sparrow (Passerculus sandwichensis nevadensis) is of intermediate size and pattern, neither strikingly large nor of notable darkness or pallor. It is characterized by brown, mottled upperparts, a white breast with streaking on the upper chest and flanks, pink legs and beak, and it’s best known field mark: a patch of bright yellow in the lores that may extend behind the eye in the supercilium. For convenience, we’ll call this the “Prairie Savannah Sparrow”. Both the Ipswich and Prairie Savannah Sparrows are highly migratory, moving between their breeding grounds across Alaska and Canada to their wintering grounds across the U.S., Mexico, covering a host of Caribbean islands, western Cuba, and Central America, particularly the Yucatan. Most Savannah Sparrows are obligate users of grassland habitats, which highlights their vulnerability over the long term, as we have a history of destroying grassland real estate. While nevadensis Savannah Sparrows can be found in saltmarsh during the winter, they are not ecologically required to be there.
Belding’s and Large-billed
The Belding’s Savannah Sparrow is a year-round resident of coastal saltmarsh from southern California and Mexico. The fourth subspecies, the Large-billed Savannah Sparrow (Passerculus sandwichensis rostratus) resides primarily in Mexico, but irrupts northward annually, reaching locations like Bolsa Chica and the shores of the Salton Sea in small numbers. The two saltmarsh Savannah Sparrow subspecies differ from the others in that their habitat is not grassland and they do not migrate in a traditional sense.
Identifying Saltmarsh Savannah Sparrows
Identifying these two saltmarsh subspecies of Savannah Sparrow is not particularly challenging with good views and a little care. Belding’s Savannah Sparrow is characterized by very dark overall coloration, both on the dorsal surface where it is darker than typical prairie Savannah Sparrows, and on the chest where the streaking is very sharply defined and almost black in color. This overall dark coloration makes the yellow supra-loral mark really “pop” visually. Large-billed Savannah Sparrow is notably larger overall than either Belding’s or Prairie Savannah Sparrows, and is much paler and grayer on the upper parts with pale brownish or tan streaking on the chest. Additionally, the Large-billed subspecies has no yellow in the lores at all, and of course, it has a notably longer and bulkier bill. Both the Belding’s and Large-billed subspecies have very poorly-defined medial crown stripes compared to the Prairie and Ipswich subspecies. Interestingly, there is little to no variation in Savannah Sparrow songs and calls across the four subspecies.
The third southern California coastal saltmarsh sparrow is the Nelson’s Sparrow, Ammodramus nelsoni. The Nelson’s Sparrow was originally part of the Sharp-tailed Sparrow complex, which was split by the American Ornithological Union in 1995 into the Saltmarsh Sharp-tailed Sparrow and the Nelson’s Sharp-tailed Sparrow. Eventually, those names were shortened to Saltmarsh Sparrow and Nelson’s Sparrow, respectively. Nelson’s Sparrow is a complex of three subspecies that breed in geographically separate locations. The largest and western-most population is the nominate race which breeds from central Canada south to the Dakotas and northwestern Minnesota. The other two races breed along the southwestern shore of Hudson Bay from Manitoba east to just barely into Quebec, and in maritime Canada around the mouth of the St. Lawrence Seaway in eastern Quebec, New Brunswick, Nova Scotia and Prince Edward Island, extending south onto the southeastern shore of Maine. The birds that winter in coastal California are almost certainly predominately of the western nominate race, A. n. nelsoni.
Idenifying Nelson’s Sparrow
Identifying Nelson’s Sparrow is not particularly difficult as the birds are visually striking and quite beautiful. Rather, the hard part is seeing them at all! While the two Savannah Sparrows are right out there to be seen and frequently vocalize to help you locate them, Nelson’s Sparrow is a skulking species that tends to be quite silent on its wintering grounds, though it occasionally offers quiet little tseep calls. The song is a sibilant hissing buzz. The trick to seeing Nelson’s Sparrows is to be present when unusually high tides force them up out of the marsh onto higher ground. Alternatively, you can stake out likely spots for hours and hope to get lucky… But it is so worth the wait. Bright individuals of this species feature a rich burnt-orange coloration in the broad supercilium, and outlining the ear coverts and the moustachial regions. A paler orange wash includes the throat, upper chest and flanks down almost to the legs. The back is mottled with a subtle purplish gray, against a darker purplish brown back with lines of white streaks for accent. The primaries are brownish with darker brown tips and pale edges. The belly is off-white to gray, and brown streaks mark the orange flanks. The ear coverts beneath the eye are again purplish gray, and they are separated from the supercilium by a dark brown post-ocular line. The overall effect is a striking and lovely sparrow.
So, there you have it: three winter-dwelling sparrows in our California coastal saltmarshes, all of which come from different places. The Belding’s Savannah Sparrow lives and breeds there all its life and is fairly common. The Large-billed Savannah Sparrow irrupts northward from Mexico in winter and is present in low numbers in limited locations. Nelson’s Sparrow migrates long distance from the middle of the continent and is present in very small numbers in widely dispersed locations. One final note: many ornithologists think that the two Savannah Sparrows are distinct full species relative to the other North American Savannah Sparrow subspecies, so a split may well be in their future. That would give these three saltmarsh sparrows another thing in common besides being winter neighbors.