Vesper sparrow (Pooecetes gramineus affinis) COSEWIC assessment and status report: chapter 3

Species Information

Name and classification

The Vesper Sparrow, Pooecetes gramineus, is one of 49 species of Emberezine sparrows that breed in North America (Sibley 2000). The species was originally known as Bay-winged Bunting (Rising 1996). Former scientific names for the species found in the literature include Poocaetes gramineus and Fringilla graminea (AOU 1957).

Four subspecies of Vesper Sparrow are recognized, three of which breed in Canada (P. g. confinis, P. g. gramineus and P. g. affinis); the fourth, P. g. altus, breeds in the southwestern United States (Jones and Cornely 2002). P. g. affinis was described in 1888 and is well accepted as a taxonomically distinct unit (AOU 1957; Rising 1996; Cannings 1998; Rogers 2000; Jones and Cornely 2002), and is the subspecies of interest for this account.

Common names for subspecies are not formally recognized by the American Ornithological Union; therefore different subspecies names are often used in different localities. P. g. affinis is sometimes referred to as the Oregon Vesper Sparrow or Coastal Vesper Sparrow (Rising 1996; Rogers 2000; Beauchesne 2002b). Throughout this status report, Coastal Vesper Sparrow will be used to refer to the affinis subspecies.

While the physical differences between P. g. affinis and P. g. confinis (its nearest geographical neighbour) are slight, their breeding ranges are separated by broad ranges of high mountains with unsuitable habitat.  They also breed in different National Ecological Areas; P. g. affinis in the Pacific EA and P. g. confinis in the Southern Mountain and Prairie EAs.

Description

The Vesper Sparrow is a medium-sized sparrow (length approximately 16 cm) with a chestnut shoulder patch (lesser coverts), white outer tail feathers, and a whitish eye-ring (Sibley 2000). Sexes are similar. Juveniles are similar to adults but duller, and usually lack chestnut coverts (Pyle 1997).

The four subspecies are similar in appearance and cannot reliably be separated in the field. Visible differences between the subspecies are limited to shading and variation in measurements. P. g. affinishas medium grayish-brown upperparts and white underparts with a buff tinge. In comparison, P. g. confinis, the nearest subspecies geographically, has pale grayish-brown upperparts and creamy underparts. P. g. affinis is slightly smaller overall than P. g. confinis; it is also has a relatively short tail in comparison with other subspecies, while P. g. confinis has a relatively long tail (Pyle 1997, Jones and Cornely 2002).

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