Migration

All populations migrate; some long distances, others short-distance altitudinal movements. Subspecies with largest wing and pectoral girdle bones (e.g., 3 northwesternmost nesting subspecies) migrate the longest distances (Swarth 1920, Zink 1987, Bell 1997; see Fig. 3), southwesternmost subspecies the shortest distances. Mean migration distance of P. i. iliaca, an eastern intermediate-distance migrant, is 1,123 km (Brewer et al. 2000).

Iliaca Group.

Late migrant in fall and early migrant in spring, reaching s. Great Lakes area by first week of Mar, ending migration by late Apr (Speirs 1985, Temple and Cary 1987, Garrett et al. 2000). Mean spring arrival date in Newfoundland (9 Apr; Threlfall and Blacquiere 1982) placed P. i. iliaca among earliest spring migrants there. Late dates in s. Ontario include 3, 4, 12, and 25 May (Speirs 1985). Spring departure dates for n.-central Texas range from 25 Mar to 5 May (Pulich 1988). Usually departs Louisiana by late Mar (Lowery 1974).

Band-recovery data indicate that breeders from Canada’s Maritime Provinces move southwest to winter on U.S. mid-Atlantic Coast (Brewer et al. 2000). Early records of migrants in s. Ontario include 22 and 28 Sep (Speirs 1985). Fox Sparrows breeding west of Hudson Bay probably winter in se. U.S. (Brewer et al. 2000). Extreme arrival dates in Texas range from 15 Oct to 3 Nov (Pulich 1988); in Louisiana, 19 Oct (Jackson 1992) and 1 Nov (Oberholser 1938).

Mean movement for banded and recaptured Red Fox Sparrows varied from 107 km for individuals banded in their hatching year (HY) to 1,009 km for those banded after hatching year (AHY; Brewer et al. 2000). Maximum movement for a HY Red Fox Sparrow was 2,126 km, for an AHY bird 2,204 km (Brewer et al. 2000).

Unalaschcensis Group.

Spring movements not well known, but bulk of movements most likely occur in late Mar and early Apr (Garrett et al. 2000), with birds arriving on breeding grounds by late Apr and early May (Gabrielson and Lincoln 1959). During fall, birds in unalaschcensis group arrive in California as early as mid-Sep (Garrett et al. 2000) with peak movement in early Oct (Desante and Ainley 1980, Garrett et al. 2000).

Migratory route apparently differs among subspecies of unalaschcensis group. P. i. annectens and P. i. townsendi migrate along coast; P. i. unalaschcensis, P. i. insularis, and P. i. sinuosa most likely make a transoceanic flight via a great circle route (shortest route between 2 points on surface of a sphere; Swarth 1920, Bell 1997; Fig. 3). If Fox Sparrows migrate via great circle routes, then migratory route of the population migrating from Unalaska I. (P. i. unalaschcensis) to s. California is among the longest ocean crossings undertaken by a land bird (Bell 1997). P. i. fuliginosa, as well as other unalaschcensis group subspecies, undoubtedly undergo altitudinal migration (Swarth 1920).

Three easternmost subspecies within unalaschcensis group (P. i. annectens, P. i. townsendi, and P. i. fuliginosa) exhibit a pattern of leapfrog migration, in which southernmost breeding subspecies (P. i. fuliginosa) migrates the shortest distance and the northernmost (P. i. annectens) migrates farthest to the south, leapfrogging over winter ranges of more southerly nesting subspecies (Swarth 1920, Zink 1987, Bell 1997; Fig. 3). Three westernmost subspecies (P. i. unalaschcensis, P. i. insularis, P. i. sinuosa), which winter the farthest south and migrate the longest distances, nest at approximately at same latitude as P. i. annectens and therefore do not fit pattern of leapfrog migration outlined by Swarth (1920, Bell 1997).

Schistacea Group.

Little known (Garrett et al. 2000). However, Slate-colored Fox Sparrows migrate much earlier than Red Fox Sparrows, with fall migrants showing up as early as late Aug (Hoover Dam, NV/AZ, 29 Aug) and spring migrants arriving on breeding grounds as early as late Mar (Garrett et al. 2000). Migrant specimens of P. i. olivacea have been identified from Stanley, WY, 23 Aug; Kemmerer, WY, 16 May; Ruby Mtns., NV, 18 Aug; Hart Mtn., OR, 14 Sep; and Beswich, CA, 19 Sep (Aldrich 1943).

Members of this group vary from nearly sedentary, with altitudinal movements, to fully migratory (Cramp and Perrins 1994). During fall, birds in the schistacea group migrate downslope from higher altitudes (Swarth 1920), and then migrate to the southwest, wintering mostly in California and n. Baja California (Garrett et al. 2000).

Megarhyncha Group.

Of all Fox Sparrows, those in megarhyncha group migrate the earliest, beginning in late Aug, with bulk of movement in Sep (Garrett et al. 2000). However, some also remain on territory as late as mid-Sep (Garrett et al. 2000). Thick-billed Fox Sparrows also migrate early in spring, with small numbers appearing at oases in California deserts as early as mid-Feb but mainly in late Mar through late Apr (Garrett et al. 2000). Nearly all Thick-billed Fox Sparrows winter in s. California and nw. Baja California (Garrett et al. 2000).

From Terrill 1968 . Migrates at night and usually arrives on breeding grounds during early-morning darkness. Regularly migrates over large expanses of open water. Migratory “fallouts” associated with severe snowstorms (Terrill 1968). In Newfoundland, males and females apparently migrate and arrive on breeding grounds at same time (Blacquiere 1979).

From Weise 1962 . Individuals kept in photoperiod chambers set at 9 h of light and 15 h of darkness for 18 mo exhibited a migratory response during spring and fall, including fat deposition and onset of Zugenruhe. Fat deposition and Zugenruhe declined and eventually disappeared by following autumn and winter, while migratory conditions developed anew in second spring of this experiment. Weise (1962) attributed fall declines and spring renewals of migratory conditions in Fox Sparrows to changes in temperature, because photoperiod was kept constant.