Appearance

See Figure 5 . The following descriptions based on Cramp and Perrins 1994, for P. i. iliaca, unless otherwise noted. Dwight’s (1900) description of molt also refers to P. i. iliaca. However, Pyle’s (1997) description of molt applies generally to all Fox Sparrow subspecies. Sexes are alike in appearance, although female may average duller in coloration (Dwight 1900).

Hatchlings

J. M. Linsdale described 2 young of P. i. megarhyncha, thought to be about 3 d old, as helpless and downy rather than feathery (Grinnell et al. 1930). Hatchlings apparently otherwise undescribed.

Juvenal Plumage

Juvenal plumage similar to Definitive Basic (adult) plumage, but body-feathers looser and softer in texture (Cramp and Perrins 1994), upperparts average duller, and underparts with buffy wash (Pyle 1997). In P. i. unalaschcensis, Dwight (1900) noted that Juvenal plumage resembled Basic I plumage but was “browner with paler edgings and more streaks above, and darker with heavier dusky streaking below” (Dwight 1900: 206). As in other passerines, outer Juvenal rectrices average more tapered than those of adults, and outer Juvenal primary-coverts somewhat narrower and more tapered than those of adults, and with narrower pale edges (Pyle 1997).

Basic I Plumage

Prebasic I molt partial; includes all median and greater wing-coverts (rarely 1 or 2 outer greater-coverts retained), usually does not include any tertials or rectrices; molt occurs on breeding grounds Jul through Sep (Dwight 1900, Pyle 1997). Basic I plumage indistinguishable from Definitive Basic plumage except for presence of retained Juvenal feathers on wings and tail, which appear more worn by spring (Dwight 1900).

Alternate I Plumage

As in Definitive Prealternate molt, Prealternate I molt, when present, limited to some head-feathers (Dwight 1900, Swarth 1920, Pyle 1997). Alternate I plumage similar to Basic I plumage, but retained Juvenal feathers may appear more worn (Pyle 1997).

Definitive Basic Plumage

Definitive Prebasic molt complete (Dwight 1900), primaries replaced in order from P1 to P9 (Cramp and Perrins 1994); molt occurs on breeding grounds from Jul through Sep (Cramp and Perrins 1994, Pyle 1997).

Definitive Basic plumage practically indistinguishable from Basic I plumage (Dwight 1900). However, AHY/after second year (ASY) birds have truncate rectrices that are unworn relative to HY/second year (SY) birds (Pyle et al. 1987). From Sep to Apr, Fox Sparrows exhibit this fresh plumage, with cap, hindneck, upper side of neck, and upper mantle medium gray with each feather tipped broad, deep rufous-chestnut. These rufous-chestnut feather tips usually partly or largely conceal gray, except for gray stripe above eye. Scapulars and lower mantle are colored deep rufous-chestnut, with sides of these feathers fringed light olive-brown or buff-brown and sometimes partially mottled rufous-chestnut contrasting with bright cinnamon-rufous or fox-red upper tail-coverts. On freshly molted feathers, tips of tail-coverts narrowly fringed pale gray buff. Lore and eye-ring mottled off-white, dull gray, and occasionally rufous eventually merging into a finely streaked off-white and rich rufous-chestnut upper cheek and shorter ear-coverts. Sometimes exhibits a short, uniform, pale-buff or off-white stripe above lore. Lower cheek and longer ear-coverts rich rufous-chestnut, often with some pale-olive or gray feather bases visible on central ear-coverts. Chestnut coloration of lower cheek broken into 2 stripes by a short off-white stripe (usually speckled chestnut) backward from side of lower mandible. One of these chestnut stripes extends back from bill commissure and other extends back from lower corner of lower mandible. White feather bases partially visible on lower side of rufous-chestnut neck. Underparts ground color pale cream to white, tinged cream-buff on lower flanks, thighs, and under tail-coverts. Chin and throat either uniform or speckled rich rufous-chestnut (occasionally joining to form a narrow band across upper throat). Breast and flanks have coarse, broad, triangular rufous-chestnut dots, sometimes coalescing into a band across breast. Chestnut marks on flanks more elongate, while upper belly and side of belly have smaller fuscous-brown or dull-black triangles. Tail deep rufous-cinnamon, with inner webs tinged brown or sooty. Remiges, greater upper primary-coverts, and alula are grayish black with an ill-defined narrow rufous-cinnamon fringe on outer web. This fringe absent from longest feather of alula. However, fringe of P9 and emarginated parts of P5–P8 are pale cinnamon to isabelline white. Lesser upper wing-coverts gray or olive-gray and suffused with a variable amount of rufous while median and greater upper wing-coverts and tertials grayish black with a broad rufous-chestnut outer fringe. Black is largely concealed, except on tertials. Median and greater wing-coverts have pale-buff to off-white spots on tips of outer webs, forming narrow broken wing-bar. Under wing-coverts and axillaries pale gray to off-white, with partial dull-gray variegation.

Definitive Alternate Plumage

Definitive Pre-alternate molt, when present, is limited to some head-feathers (Dwight 1900, Swarth 1920, Pyle 1997); occurring Mar through Apr (Pyle 1997).

Definitive Alternate plumage similar to Definitive Basic plumage except for subtle differences due mainly to wear and fading. From roughly May through Jul, rufous-chestnut feather-tips of Definitive Basic plumage, which are found from cap to upper mantle, are partly or fully worn. Plumage from cap to upper mantle mainly gray with traces of chestnut spots or brown suffusion, especially on crown. Amount of chestnut and gray on cap and neck is individually variable, in part due to individual differences in abrasion and in part due to geographic origin. Birds from the East (e.g., Nova Scotia) tend to have more extensive chestnut and rufous tones, while farther west (e.g., Wisconsin), birds are grayer. Scapulars and lower mantle olive-brown to grayish with deep rufous-chestnut streaks. White stripe backward from lower mandible and pale olive-gray center to ear-coverts often more distinct than in Definitive Basic plumage, and there is usually a prominent white bar at lower rear of ear-coverts. Triangular rufous spots on underparts narrower and smaller and tend to coalesce less than in Definitive Basic plumage. Lower flanks and under tail-coverts have a cream-white ground color, with spots on tips of median and greater upper wing-coverts whiter, but sometimes worn off.

Bill And Gape

Bill grayish brown, dusky brown, dark plumbeous gray, or grayish black with basal half of lower mandible yellow, orange-flesh, yellow-orange, bright orange, or pinkish gray (Cramp and Perrins 1994). Data from recent specimens of various subspecies indicate that upper mandible coloration is dark horn, blackish horn, or blackish brown with pale (yellow or orange) edges (ramus, gape, and base; LSUMNS). However, lower mandible coloration greenish yellow, dull orange-yellow, dull yellow, or blue-gray (LSUMNS). On many speci-mens, pale lower mandible coloration blends and becomes darker toward dark bill-tip (LSUMNS). Presence or absence and intensity of yellow or orange coloration at base of mandible variable among populations, and is possibly seasonally variable (Garrett et al. 2000). While most Sooty Fox Sparrow populations have a rich orangish or yellowish base to mandible, Thick-billed Fox Sparrows have a grayish or gray-green base (Garrett et al. 2000). Soft-part colors also vary with age. At Hume, Fresno Co., CA, younger nestlings had gray-yellow upper mandible and yellow lower mandible, while older nestlings had entire bill pink, pink-brown, or occasionally gray-brown, with a yellow gape (LSUMNS). Fledglings had gray-brown or light-brown bill with yellow gape (LSUMNS).

Iris

Dark brown or red-brown, independent of age or sex (LSUMNS, UWBM).

Legs And Feet

Dull flesh-gray, purplish brown-gray, brownish pink, light brown, dark brown, horn brown, or dark horn brown (Cramp and Perrins 1994, LSUMNS). Nestlings and fledglings from Hume, Fresno Co., CA (boundary between stephensi and megarhyncha) apparently have yellow, pink, or pinkish-brown legs and feet, with some birds showing pink coloration above and yellow below (LSUMNS).