Migration

Figure 4. Annual cycle of breeding, migration, and molt.

Nature Of Migration In The Species

A partial migrant. Most populations north of a line from Massachusetts through n. Kansas migrate into s. U.S. in autumn; scattered individuals may remain north. Populations south of the line can migrate further south, be year-round residents, or move only short distances to form winter flocks (Laskey 1934, Fretwell 1968). Fall migration generally moves birds to areas in which average Jan temperature does not drop below -7° C (Root 1988).

Timing And Routes Of Migration

Routes not described. In ne. Pennsylvania (1987–2006), earliest male arrival ranged from 1 Apr – 19 Apr; mean male arrival dates ranged from 17 Apr – 2 May. Earliest female arrivals ranged from 13 Apr – 27 Apr; average female arrival dates ranged from 29 Apr – 16 May (MC). Autumnal departure in this population not well documented, but latest individuals had left by end of Oct (MC; see Fig. 4). In s.-central Michigan (1939-1948), earliest male arrivals ranged from 22 Mar – 7 Apr, with a median date of 2 Apr. Earliest female arrivals ranged from 14 Apr – 27 Apr (Walkinshaw 1978). Earliest male arrival in s. New York (1988–1989) 16 Mar, with a mean arrival date of 12 April (DAN).

In Tennessee, northward movement of migrants begins in Feb and peaks in Mar; southward in Oct, with peak in Nov (Laskey 1934). In general, as latitude increases, spring migrants appear at later dates and fall migrants depart earlier (Roberts 1936, Todd 1940, Walkinshaw 1968a). In spring males arrive 2–3 wk earlier than females (Walkinshaw 1968a, MC); no difference in arrival dates of banded vs. unbanded (old vs. young?) males (DAN, MC). Annual variation in spring arrival dates is correlated with average spring temperatures (Walkinshaw 1978, MC).

Migratory Behavior

Methods of orientation, altitude, flocking, and flight formations not described. Appears to migrate slowly spring and fall, spending days or weeks in the same area before moving on. Cold spring weather delays migration (Laskey 1934). In ne. Pennsylvania, earliest male arrival (4 Apr 1991) was in a year with higher than normal Mar/Apr temperatures; latest first male date, 17 Apr 1989, in an unusually cold spring (MC). Migration is nocturnal (Walkinshaw 1968a).

Control And Physiology Of Migration

Photoperiod effects and hormonal controls not described. Captive sparrows show an increase in mass, body protein, and lipid content in fall and a decrease in spring, although Olson and Kendeigh (1980) interpret this as an acclimation response to seasonal temperature change. They note no increased fat deposition prior to migratory periods; their birds did exhibit nocturnal restlessness in both spring and fall.