The Savannah Sparrow (Passerculus sandwichensis) is a small sparrow. It is the only member of the genus Passerculus (Bonaparte, 1838). Recent comparison of mtDNA NADH dehydrogenase subunit 2 and 3 sequences (Zink et al., 2005) indicates that the Ipswich Sparrow, formerly usually considered a good species (as Passerculus princeps), is a well-marked subspecies of the Savannah Sparrow, whereas the 2 southwestern subspecies should be recognized as distinct species.

This passerine bird breeds in Alaska, Canada, northern, central and Pacific coastal USA, Mexico and Guatemala. The Pacific and Mexican breeders are resident, but other populations are migratory, wintering from the southern United States to northern South America. It is a very rare vagrant to western Europe.

Savannah Sparrow is a very variable species, with numerous races, several of which have been split as separate species at various times. The different forms vary principally in the darkness of the plumage, with Alaskan and interior races the palest, and southern Pacific coastal forms the darkest.

This species has a typically sparrow-like dark-streaked brown back, and whitish underparts with brown or blackish breast and flank streaking. It has yellowish or whitish crown and eyebrow stripes. The cheeks are brown and the throat white.

The breeding habitat is a wide variety of open habitats including grasslands and cultivation. Savannah Sparrows nest on the ground, laying 3-6 eggs in a cup nest sheltered by a clump of grass or other vegetation. They form flocks in the winter to migrate.

These birds forage on the ground or in low bushes. They mainly eat seeds, but insects are also eaten in the breeding season. The song is mixture of chips and trills. The flight call is a thin seep.

This bird was named after Savannah, Georgia where one of the first specimens of this bird was collected.

Although this bird is generally abundant across its range, some coastal populations depending on salt marsh habitat are declining.

Fifteen subspecies plus the two Large-billed Sparrows are currently recognized. Four additional subspecies are not generally accepted. The subspecies are usually divided into several groups.

The Savannah Sparrows proper are very similar and migrant birds can not usually be related to a breeding population with certainty. The resident or partially migratory subspecies are well distinguishable by size and, particularly between groups, coloration. The Ipswich Sparrow is somewhat larger and paler in colour than other eastern Savannah Sparrows. The breast streaks are narrower and pale brown. Some birds overwinter on the island; others migrate south along the Atlantic coast, usually departing later and returning sooner than mainland birds. Some birds interbreed with P. s. savanna in Nova Scotia. These birds frequently raise three broods in a year. This bird was first observed in winter on the dunes near the town of Ipswich, Massachusetts.

Seventeen subspecies (including the Large-billed Sparrows) are currently recognized. Four additional subspecies are not generally accepted. The subspecies are usually divided into several groups:

All are migratory.

P. s. labradorius, breeds in Newfoundland, Labrador, and N Quebec

P. s. oblitus, breeds in N Ontario and Manitoba

P. s. savanna (Eastern Savannah Sparrow), breeds in the NE USA and adjacent Canada (includes P. s. mediogriseus)

P. s. sandwichensis (Aleutian Savannah Sparrow), breeds on the Aleutian Islands and W Alaskan Peninsula

P. s. anthinus, breeds in the remainder of Alaska, south and east to central British Columbia and north of the Great Plains to Manitoba

P. s. brooksi (Dwarf Savannah Sparrow), breeds in southernmost British Columbia to northernmost California

P. s. alaudinus, breeds in coastal northern and central California

P. s. nevadensis, breeds in the N Great Plains and the Great Basin

P. s. brunnescens, breeds from central Mexico south to Guatemala (includes P. s. rufofuscus)

P. s. wetmorei is a doubtful subspecies which may breed in the mountains of Guatemala. It is known from only 5 specimens, collected June 11-17, 1897, in Huehuetenango Department.[citation needed]

Formerly considered a distinct species, some post-breeding dispersal.

P. s. princeps, breeds almost exclusively on Sable Island

The Ipswich Sparrow is somewhat larger and paler in colour than other eastern Savannah Sparrows. The breast streaks are narrower and pale brown. Some birds overwinter on the island; others migrate south along the Atlantic coast, usually departing later and returning sooner than mainland birds. Some birds interbreed with P. s. savanna in Nova Scotia. These birds frequently raise three broods in a year. This bird was first observed in winter on the dunes near the town of Ipswich, Massachusetts.

The Large-billed Sparrows proper are 2-3 dark, large and strong-billed subspecies:

Passerculus rostratus rostratus (or P. s. rostratus), which breed on the Gulf Coast of NE Baja California and NW Sonora (some post-breeding dispersal).

P. r. atratus (or P. s. atratus), resident on the coast of central Sonora to central Sinaloa (resident)

The Belding's (Savannah/Large-billed) Sparrows are all-year residents of salt marshes of the Californian Pacific coast. They are dark, rufous, and have rather long but not very hefty bills.

P. r. beldingi (or P. s. beldingi), resident on the Pacific Coast from Morro Bay, California, to El Rosario, Baja California (includes P. r./s. bryanti)

P. r. anulus (or P. s. anulus), resident around Sebastián Vizcaíno Bay, Baja California

P. r. guttatus (or P. s. guttatus), resident around San Ignacio Lagoon

P. r. magdalenae (or P. s. magdalenae), resident around Magdalena Bay

The San Benito (Savannah/Large-billed) Sparrow is a resident bird of the Islas San Benito off Baja California; a stray bird was observed on Cedros Island on April 21, 1906

P. r. sanctorum (or P. s. sanctorum)

This is a large-bodied and large-billed subspecies, similar to rostratus. They utilize different habitat and their breeding season does not seem to coincide with that of Belding's Sparrows. However, their bill size is due to convergent evolution and their habitat choice simply to the lack of alternatives on their barren island home; altogether, it appears to be a fairly recent offshoot from the Belding's Sparrows group. It appears as distinct evolutionarily from these as does the Ipswich Sparrow from the Savannah Sparrow proper group, only that there seems to have been more gene flow and/or a larger founder population in the case of the latter.