Systematics

Varies geographically in plumage coloration, relative lengths of wing and tail, and bill shape and size. Subspecies generally fit into 1 of 4 groups (see Distinguishing characteristics, above), which are well defined by plumage (Swarth 1920), morphometrics (Linsdale 1928a, Zink 1986), and genetics (Zink 1994, Zink and Weckstein in press). Within each of these 4 species groups, geographic variation in plumage and morphology is considerable. Iliaca group characterized by bright-reddish coloration with a grayish crown and nape, tail shorter than wings, and a medium-sized bill (Swarth 1920); this group also shows a pale triangular patch above end of pale submoustachial-stripe, which is not obvious in other Fox Sparrow groups (Rising 1995). Within iliaca group, subspecies vary from east to west, with western birds tending to have a grayer head and nape and browner ventral streaking and malar-stripe (Rising 1995, 1996). Unalaschcensis group consists of dark-brown to sooty-plumaged birds with tail shorter than wings and a medium-sized bill (Swarth 1920); face of those in this group nearly uniform brown in both lores and submoustachial area, lacking typically light-colored lores found on birds in the other 3 groups (Rising 1995, Zink and Kessen 1999). Subspecies in unalaschcensis group vary clinally in both size and coloration. Coloration varies from dark brown with a reddish wash in the north to sooty brown in the south (Swarth 1920). Within unalaschcensis group, sub-species in the north are generally larger bodied and larger billed than those in the south (Rising 1996). Schistacea group consists of birds with reddish wings and tail, brownish gray to slaty-gray crown and back, tail usually longer than wings and medium-sized bill (Swarth 1920, Rising 1996). Schistacea group varies clinally from north to south, with amount of gray in crown and back and bill size in-creasing from north to south (Swarth 1920). Megarhyncha group consists of birds with reddish wings and tail, grayish-brown to ashen-gray crown and back, tail usually longer than wings, and large-sized bill (Swarth 1920, Zink and Kessen 1999). Large bill size and call note (see Sounds: vocalizations, below) distinguishes birds in megarhyncha group from others. Megarhyncha group has an almost identical pattern of variation to that of schistacea group, with amount of gray in crown and back and bill size increasing from north to south (Swarth 1920, Zink and Kessen 1999).

Zink’s (1986) analysis of allozymes found little or no protein differentiation among morphologically and geographically diverse samples of western populations of Fox Sparrows, whereas analyses of mitochondrial DNA (mtDNA) detected significant amounts of genetic structure, identifying 4 groups of Fox Sparrows corresponding to those defined by plumage and morphology (Zink 1994, Zink and Blackwell 1996). Although phylogenetic relationships among the 4 groups of Fox Sparrows are equivocal (Zink and Weckstein in press), megarhyncha and schistacea groups, which are most similar in plumage and morphology, are almost certainly not each other’s closest relatives (Zink 1994, Zink and Blackwell 1996, Zink and Weckstein in press). Patterns of mtDNA variation suggest that hybridization between these 4 groups is limited between all pairs of taxa except megarhyncha and schistacea groups (Zink 1994). Zink (1994) found evidence of a narrow contact zone between these 2 groups along the interface of the Great Basin and Sierra Nevada-Cascade axis. Megarhyncha and schistacea groups also intergrade morphometrically, although over a broader area than the contact zone (Zink 1994). A complex pattern of hybridization exists at the interface of unalaschcensis, iliaca, and schistacea groups, where they meet in British Columbia, Yukon, Alberta, and Alaska (Williamson and Peyton 1962, Webster 1975, Zink 1994). Nine of 139 individuals from this region carried the “wrong” mitochondrial DNA haplotype, most likely indicating low levels of hybridization (Zink 1994). More genetic work needed, especially at interfaces between Fox Sparrow groups.

Subspecific taxonomy has changed over time from 16 subspecies recognized by Swarth (1920) and Linsdale (1928a) to 18 subspecies recognized by Am. Ornithol. Union (1957). Many of these are weakly differentiated taxa. Swarth (1920), studied external morphology and recognized 3 main groups of subspecies: iliaca group (iliaca, altivagans), unalaschcensis group (unalaschcensis, insularis, sinuosa, annectens, townsendi, fuliginosa), and schistacea group (schistacea, megarhyncha, mariposae, stephensi, brevicauda, fulva, canescens, monoensis). A few subspecies were not yet described at the time of his study. Subsequently, Am. Ornithol. Union (1957) recognized 18 subspecies of Fox Sparrow including: P. i. iliaca, P. i. zaboria, P. i. altivagans, P. i. unalaschcensis, P. i. insularis, P. i. sinuosa, P. i. annectens, P. i. townsendi, P. i. fuliginosa, P. i. olivacea, P. i. schistacea, P. i. swarthi, P. i. canescens, P. i. fulva, P. i. monoensis, P. i. megarhyncha, P. i. brevicauda, and P. i. stephensi . Two additional subspecies, P. i. mariposae (Swarth 1918) and P. i. chilcatensis (Webster 1983) have been described but are not widely recognized.

Based on morphometric and allozyme data, Zink (1986) hypothesized that iliaca, unalaschcensis, and schistacea groups were at least 3 distinct species; however, his analysis of mtDNA variation (Zink 1994) suggested that the Fox Sparrow is in fact 4 species, Red Fox Sparrow, P. iliaca (including races P. i. zaboria and P. i. iliaca), Sooty Fox Sparrow, P. unalaschcensis (including P. u. unalaschcensis, P. u. insularis, P. u. sinuosa, P. u. annectens, P. u. townsendi, and P. u. fuliginosa), Slate-colored Fox Sparrow, P. schistacea (including P. s. altivagans, P. s. olivacea, P. s. schistacea, P. s. swarthi, and P. s. canescens), and Large-billed Fox Sparrow, P. megarhyncha (including P. m. fulva, P. m. brevicauda, P. m. mariposae [= megarhyncha], P. m. monoensis, and P. m. stephensi). Analysis of MtDNA only resolves these 4 major groups and was unable to distinguish subspecies as defined by morphology (Zink 1994). Rising (1996) recognized 3 groups, lumping schistacea and megarhyncha groups. Am. Ornithol. Union (1998) recognized the 4 groups at informal rank of subspecies group and suggested that, based on genetic evidence (Zink 1986, 1991, 1994) and morphology (including plumage coloration), the 4 groups each may represent a biological species. Before these groups are recognized as separate species, additional study is needed in contact zones between groups, especially along hybrid zone between schistacea and megarhyncha (Am. Ornithol. Union 1998).

Red Fox Sparrow (Iliaca Group)

P. i. iliaca Merrem, 1786. Breeds from ne. Manitoba, n. Ontario, n. Quebec, n. Labrador, and n. Newfoundland south to n.-central Ontario, s. Quebec, extreme nw. Maine, nw. New Brunswick, Prince Edward I., coastal Nova Scotia, and s. Newfoundland (Swarth 1920, Am. Ornithol. Union 1957, Adamus 1987, Rising 1987, Erskine 1992, Bisson and Limoges 1996). Winters from s. Wisconsin, s. Michigan, southernmost Ontario, central Pennsylvania, se. New York, n. Massachusetts, s. New Hampshire, coastal Maine, coastal New Brunswick (very rare), coastal Nova Scotia (local) and coastal s. Newfoundland (local) south to s. Mississippi, s. Alabama, and n. Florida (Am. Ornithol. Union 1957, CBC data). P. i. iliaca can be distinguished from all subspecies in schistacea group by different proportions in wing and tail lengths (wing longer than tail in iliaca, wing equal to or shorter than tail in schistacea group) and overall bright-ruddy plumage coloration. The much brighter hue of reddish markings, sharply contrasting red-and-gray dorsal streaking, and heavier and more stubby bill distinguish iliaca from all subspecies within unalaschcensis group. P. i. iliaca distinguished from altivagans by greater general size and brighter, more ruddy coloration, with more sharply defined dorsal streaking (Swarth 1920).

P. i. zaboria Oberholser, 1946 . Breeds from n. Manitoba west through extreme sw. Nunavut, sw. Northwest Territories, n. Yukon, to nw. and interior Alaska and south to n.-central Manitoba, central Saskatchewan, s.-central Alberta, and n. British Columbia (south to Dease Lake, Peace River parklands; Oberholser 1946, Am. Ornithol. Union 1957, Godfrey 1986). Winters east of Great Plains from se. Minnesota, central and e. Iowa, se. Kansas, and central and e. Oklahoma south to s. Texas, Louisiana, Mississippi, Alabama, and n. Georgia. Rarely winters in w. U.S. (Am. Ornithol. Union 1957). This subspecies was split from iliaca by Oberholser (1946), because its upperparts, including wings and tail, average darker and more grayish or sooty. Oberholser (1946) also noted that zaboria ’s reddish-brown breast-spots usually smaller, less numerous, and duller than those in iliaca . However, Rising (1995) states that although very gray individuals are probably zaboria; iliaca and zaboria cannot be reliably separated.

Sooty Fox Sparrow (Unalaschcensis Group)

P. i. unalaschcensis Gmelin, 1789. Breeds from Unalaska I. (in e. Aleutians) to Shumagin and Semidi Is. and Alaska Peninsula (Swarth 1920, Am. Ornithol. Union 1957). Winters from s. British Columbia south to extreme s. California and rarely to n. Baja California (Swarth 1920, Am. Ornithol. Union 1957, Garrett et al. 2000). Two morphologically diagnosable groups of unalaschcensis winter in California: one with long, pointed bill and pale-brownish plumage that is ashy in tone and one with plumage darker in appearance and plumbeous in tone, with a shorter/heavier bill (Swarth 1920). Birds from Alaska Peninsula show range of variation, possibly indicative of intergradation with sinuosa to the southeast and insularis to the south (Swarth 1920).

P. i. townsendi Audubon, 1838. Breeds on islands and mainland in se. Alaska from Glacier Bay south to Queen Charlotte Is., British Columbia (Swarth 1920, Am. Ornithol. Union 1957). Winters along coast from breeding range south to central California (Swarth 1920, Am. Ornithol. Union 1957). Coloration much darker and more rufescent, and breast-spots larger and more crowded than other sub-species from unalaschcensis group to the north and brighter colored and less sooty than fuliginosa to the south (Swarth 1920).

P. i. fuliginosa Ridgway, 1899 . Breeds on mainland coast of se. Alaska (south of Stikine River) and coastal British Columbia, except Queen Charlotte Is., south to nw. Washington (Ridgway 1899, Swarth 1920, Am. Ornithol. Union 1957). Winters from sw. British Columbia south to coastal central California (Ridgway 1899, Swarth 1920, Am. Ornithol. Union 1957). Darker and less rufescent when compared to similar P. i. townsendi to its north. Breast-spots dark sooty brown, and larger and more confluent than in other forms (Ridgway 1899).

P. i. annectens Ridgway, 1900 . Breeds on coast of s. Alaska, from Cross Sound to north shore of Yukutat Bay (Ridgway 1900, Am. Ornithol. Union 1957). Most winter along coast of central California (Swarth 1920). Intermediate in plumage and morphology between sinuosa to the north and townsendi to the south. Plumage brighter and more ruddy than sinuosa but not as dark as townsendi (Swarth 1920). Breast-spotting sparser than townsendi (Swarth 1920). Slightly smaller in bill and body size than subspecies to the north and larger than townsendi to the south (Swarth 1920).

P. i. insularis Ridgway, 1900 . Breeds on Kodiak I. and winters southward along Pacific Coast to extreme s. California (Ridgway 1900, Am. Ornithol. Union 1957). Similar to unalaschcensis, but brighter, ruddier, and more uniform above (Swarth 1920). Spots on chest larger and deeper brown. Under tail-coverts tinged with buff (Ridgway 1900). Bill of insularis is heavier in structure than sinuosa but about the same bulk as unalaschcensis (Swarth 1920).

P. i. sinuosa Grinnell, 1910 . Breeds in Prince William Sound and Kenai Peninsula districts and on Middleton I. (Grinnell 1910, Am. Ornithol. Union 1957). Winters south along Pacific slope of s. California (Swarth 1920). Bill of sinuosa more slender, and breast-spotting larger and heavier than in unalaschcensis . Plumage more reddish than unalaschcensis, but less than in brighter-colored insularis and darker-colored annectens and townsendi (Grinnell 1910, Swarth 1920).

P. i. chilcatensis Webster, 1983 . Described from mainland of se. Alaska and adjacent Canada. According to Webster (1983), chilcatensis breeds from Chilkat River area of British Columbia and Alaska southeast to Tewart area of British Columbia and winters from coastal Oregon south through coastal counties of n. California to San Francisco Bay region, although Grinnell and Miller (1944) cited additional specimens from Monterey, Los Angeles, Siskiyou, Shasta, and Lassen Cos. A few wintering specimens examined by Webster (1983) were collected farther north, one on Prince of Wales I., AK, and one at Puget Sound, WA (Webster 1983). Webster (1983) split chilcatensis from fuliginosa . Although Swarth (1920) did not formally recognize the division of fuliginosa into 2 subspecies, he suggested that fuliginosa might need subdivision and called birds like those described by Webster (1983) “non-typical fuliginosa .” According to Webster (1983), chilcatensis is less reddish, duller in color and has a shorter tail than fuliginosa . However, most authors (Zink 1994, Rising 1996, Zink and Kessen 1999), do not recognize chilcatensis, presumably because chilcatensis is an arbitrary point on a cline and not a distinct taxon.

Slate-Colored Fox Sparrow (Schistacea Group)

P. i. schistacea Baird, 1858. Breeds from se. British Columbia (Crowsnest Pass) and sw. Alberta (Waterton Lakes Park) south through high mountains of the Great Basin region, including n.-central and e. Oregon (Cascade Mtns. south to Warm Springs; Howard; Wallowa Mtns.), and w. Montana (Jud-ith River, Red Lodge) south to n.-central and ne. Nevada (breeding recently confirmed in mountains of ne. Humboldt Co. and central Elko Co.; Nevada BBA 1997–2000 unpubl.) and sw. Wyoming (Fort Bridger), and western half of Colorado (Cochetopa Creek; Swarth 1920, Am. Ornithol. Union 1957). Winters along coast, coastal ranges, and both central and s. Sierra Nevada of s. California (Swarth 1920, Garrett et al. 2000). P. i. schistacea has slate-colored head, slate-colored back washed with brown (mouse gray), brown wings and rump, rusty-brown tail, and breast and flanks heavily spotted with dark brown (Rising 1996). Bill of schistacea smaller than that of birds in megarhyncha group and overlaps considerably with other subspecies in schistacea group.

P. i. altivagans Riley, 1911 . Breeds from interior central British Columbia southeast to mountains of se. British Columbia and sw. Alberta (Am. Ornithol. Union 1957). Winters principally in Cascades and Sierra Nevada of California, coastal s. California, and nw. Baja California (Am. Ornithol. Union 1957). Plumage coloration similar to schistacea; however, middle of back brown rather than mouse gray, and wings and tail more reddish brown (burnt umber; Riley 1911). Although Riley (1911) noted similarity between altivagans and schistacea, Swarth (1920) considered altivagans to be a member of iliaca group. However, both Rising (1987) and Zink (1994) classify altivagans as a member of schistacea group, as indicated by both voice (Martin 1977) and mitochondrial DNA (Zink 1994). Populations within altivagans have considerable variation, with some darker-colored birds, dark reddish brown above and heavily spotted below, and other lighter-colored birds, predominantly grayish above and sparsely spotted below (Swarth 1920). These variants may indicate intergradation with neighboring subspecies (Swarth 1920). Darker birds are probably intergrades with unalaschcensis (fuliginosa), lighter ones are intergrades with iliaca group (with P. i. zaboria). P. i. altivagans also known to intergrade with schistacea near Banff, Alberta (Am. Ornithol. Union 1957), and olivacea, as noted by Swarth (1920), who found some duller birds that had less reddish coloration and tail length roughly equal to wing length.

P. i. canescens Swarth, 1918 . Breeds in central Nevada (Shoshone, Toiyabe, Monitor Mtns.) and extreme central e. California (White Mtns.; Swarth 1918, Am. Ornithol. Union 1957). Breeding recently confirmed over somewhat broader range in central Nevada, including mountains of se. Churchill, n. Nye, and s. and e. White Pine Cos. (Nevada BBA 1997–2000 unpubl.). Winters in s. California, n. Baja California, and s. Arizona (Swarth 1920, Am. Ornithol. Union 1957). Similar to schistacea but grayer (Swarth 1918).

P. i. olivacea Aldrich, 1943 . Breeds from sw. and s.-central British Columbia (Mt. McLean, Nelson) south through central and e. Washington on east slopes of Cascade Mtns. of Washington, eastward to at least Blue Mtns. of Washington and Oregon, mountains of ne. Washington, and probably to n. Idaho and nw. Montana (Aldrich 1943, Am. Ornithol. Union 1957). Winters in interior California (Tehama Co., Piute Mtns.) and n. Baja California (Sierra Juárez). P. i. olivacea similar to schistacea in Wyoming, but darker and more olivaceous (Aldrich 1943). P. i. olivacea is dark hair brown to olive-brown above, rather than light hair brown to light olive-brown, and edges of wing- and tail-feathers and upper tail-coverts are Brussels brown to Argus brown, rather than cinnamon brown (Aldrich 1943). Olivacea also similar to fulva of central Oregon but more brownish with dark hair-brown to olive-brown plumage above, rather than cinnamon brown to Prout’s brown. Bill of olivacea shorter and more slender than fulva ’s (Aldrich 1943). Intergrades with schistacea to its east (Aldrich 1943).

P. i. swarthi Behle and Selander, 1951 . Breeds from se. Idaho (Bannock and Bear Lake Cos.) through n.-central Utah (Raft River Mtns., Deep Creek Mtns., Wasatch Mtns. south to Sanpete Co.; Behle and Selander 1951, Am. Ornithol. Union 1957). Winter range unknown (Behle and Selander 1951, Am. Ornithol. Union 1957). Grayer on head and back, and breast-streaking heavier and less rufescent than schistacea . Most similar to canescens, but grayer (Behle and Selander 1951). Behle and Selander (1951) suggest that in northern, northwestern, and eastern portions of its range, swarthi is connected by clines to schistacea . Probably also connected by clines to canescens (Behle and Selander 1951).

Large-Billed Fox Sparrow (Megarhyncha Group)

P. i. megarhyncha Baird, 1858. Breeds from sw. Oregon (Onion Mtn., Robinson’s Butte) south through central n. California (Siskiyou Mtns. at Del Norte Co. line and Mt. Orr, head of Dog Creek) and Sierra Nevada of California south to Kearsarge Pass (Swarth 1920, Am. Ornithol. Union 1957). In central Sierra Nevada (Mono Lake district) breeds only on western flank (Swarth 1920, Am. Ornithol. Union 1957). Winters in central and s. California and nw. Baja California (Am. Ornithol. Union 1957). Intermediate in bill size, tail length, and general body size between monoensis and stephensi . Characteristics and geographic distribution of mega-rhyncha as recognized by Zink (1986) and Rising (1996) are identical to those of mariposae, as recognized by Swarth (1918). Zink (1986) and Rising (1996) have accordingly synonymized Swarth’s (1918) mariposae with megarhyncha, the older name. Connected to stephensi by a cline of morphological and plumage variation (Zink 1986).

P. i. stephensi Anthony, 1895 . Breeds in s. Sierra Nevada from Sierras of s. California; Hume and Horse Corral Meadow (Fresno Co. through Tulare Co.), summit of Mt. Pinos (Ventura Co.), San Gabriel Mtns. (Los Angeles Co.), San Bernardino Mtns. (San Bernardino Co.) and San Jacinto Mtns. (River-side Co.; Swarth 1920) to n. Baja California in Sierra San Mártir (Erickson and Wurster 1998). Primarily winters at lower elevations in s. California (Am. Ornithol. Union 1957). P. i. stephensi most similar to megarhyncha, but generally larger in body size and has a larger bill (Anthony 1895). Relatively enormous bill of stephensi distinguishes it from all other Fox Sparrows. Stephensi can be told from brevicauda by its more slenderly pointed bill, more grayish plumage coloration, and longer tail. Stephensi is southernmost extreme in cline of increasing bill size, increasing tail length, and more grayish plumage coloration, when compared with other sub-species in megarhyncha group (Swarth 1920, Zink 1986).

P. i. monoensis Grinnell and Storer, 1917 . Breeds in California’s Mono district on eastern flank of central Sierra Nevada (Woodfords, Mammoth, Benton) and in Mineral Co., NV (Walker River Range; Am. Ornithol. Union 1957). Winters in central interior and s.-coastal California, south to nw. Baja California (Am. Ornithol. Union 1957). Closely resembles megarhyncha, but has a less robust bill and slightly (paler) ashier gray on upper parts (Grinnell and Storer 1917). Bill thicker and dorsal coloration paler than in schistacea (Grinnell and Storer 1917).

P. i. brevicauda Mailliard, 1918 . Breeds in northern and inner coast ranges of California, from Yolla Bolly Mtns. (at junction of Trinity, Tehama, and Mendocino Cos.) south to Snow Mtn. (Colusa Co.) and Mt. Sanhedrin (Mendocino Co.; Mailliard 1918, Swarth 1920, Am. Ornithol. Union 1957). Winters in coastal central and s. California (Swarth 1920, Am. Ornithol. Union 1957). Brevicauda is relatively large billed and is similar to stephensi; however, head, neck, back, and breast-spots more fuscous brown, rather than the mouse gray of stephensi (Mailliard 1918). Body size nearly identical to stephensi, but with a relatively shorter tail, hence the name brevicauda (Mailliard 1918).

P. i. fulva Swarth, 1918 . Originally described from a specimen collected in Warner Mtns. of Modoc Co., CA. Fulva breeds from central Oregon, east of Cascades (Sisters, Keno, Steens Mtns.) into extreme ne. California (Modoc, Lassen Cos.; Swarth 1920, Am. Ornithol. Union 1957). Winters from sw. California to n. Baja California (Am. Ornithol. Union 1957). Bill of fulva intermediate in size between schistacea and megarhyncha, which is similar but more slender and attenuated than that of monoensis (Swarth 1918, 1920). Wing and tail measurements similar to schistacea, but shorter than in megarhyncha (Swarth 1918, 1920). Overall plumage coloration of fulva more brownish than megarhyncha and monoensis, which is similar to schistacea (Swarth 1918, 1920).

P. i. mariposae Swarth, 1918 . Originally described from a bird collected near Chinquapin, in Yosemite National Park, CA. According to Swarth (1918, 1920), mariposae breeds from Siskiyou Co., CA, from the head of Little Shasta River, south at least to Yosemite National Park region on west slope of Sierra Nevada and to Kearsarge Pass on east slope of Sierra Nevada. Mariposae is intermediate in bill structure between monoensis and stephensi and is nearly identical in plumage coloration to canescens, monoensis, and stephensi . Zink (1986) and Rising (1996) synonymized mariposae with megarhyncha, the name that has priority for this form.

Historically, Fox Sparrow thought to be closely related to Song Sparrow (Paynter 1964), because of their similarity in plumage coloration, morphology, song, and nesting habits (Swarth 1920, Rising 1996, Patten and Fugate 1998). Linsdale (1928b) considered Song Sparrow to be so similar to Fox Sparrow that he merged genus Melospiza into genus Passerella . Zink (1982) suggested that this generic merger would obscure significant amount of genetic differentiation found in comparisons of proteins (allozymes) between these taxa. Furthermore, mtDNA sequence analyses (Zink and Blackwell 1996) suggested that Passerella was not at all closely related to Melospiza . Zink and Blackwell’s (1996) mtDNA sequence data suggested that Passerella was most closely related to a clade of sparrows including Zonotrichia and Junco . Most recent molecular evidence (also mtDNA sequences) identified American Tree Sparrow (Spizella arborea) as sister to Fox Sparrow, with this pair sister to a Junco-Zonotrichia clade (J. Klicka pers. comm.). While phylogenetic data strongly supported that Spizella arborea, Junco, and Zonotrichia were closest living relatives of Passerella, genetic distance between Passerella and its closest living relatives was relatively high (greater than 11% mtDNA sequence divergence; Zink and Weckstein in press), indicating that no close extant relatives exist (J. Klicka pers. comm.).