Savannah Sparrow Passerculus sandvicensis
Corrections and updates to the Guide:
In WA all birds are in between reddish and grayish types shown in the Sibley Guide; coastal breeders dark-striped but not as extreme as beldingi, interior birds close to grayish type; some large Aleutian breeders winter on coast. (fide D. Paulson).
“…in many ways intermediate between northern [typical] and “Large-billed” Savannah Sparrows. …alongside the migratory northern subspecies the Belding’s Savannah Sparrows in southern California seem quite distinctive.”
Subspecies illustrated in the Sibley Guides
Typical P. s. savanna group
Ipswich P. s. princeps
Belding’s P. s. beldingi
Aleutian P. s. sandwichensis group
Large-billed Sparrow P. s. rostratus group
The five subspecies groups listed above are illustrated in the Sibley Guide, representing a widespread continental or “typical” form and four other recognizable populations with restricted ranges. Variation in this species is considerable with about 25 named subspecies across North America.
Most variation is clinal, however, and only a few subspecies and subspecies groups are really distinguishable. In general subspecies in the east and in humid Pacific coastal areas are more rufous, while those in the drier interior are gray, but there is considerable variation and I found it difficult to separate broad eastern and western groups among the continental birds.
Of the groups recognized here the most distinctive in plumage, structure, voice and DNA is the Large-billed group, which has been proposed for species status. In the past Ipswich has been considered a separate species, a treatment supported by its isolation during the breeding season and clearly different size and plumage, but this subspecies apparently interbreeds freely with mainland birds when they come in contact.
Rising 2010. The Many Savannah Sparrows. Birding 42(6): 44-55.