1514 U.S. NATIONAL MUSEUM BULLETIN 2-3 7 part 3 



Spring.— The spring migration normally showed two main flights: 

 an early migration of breeding males in late February or early March, 

 and the main flight of breeding males and females, and also transients, 

 in the middle of March. The early migration was absolutely de- 

 pendent on a warm wave the last of February or the first of March, 

 but the main migration was only relatively dependent on a rise in 

 temperature. Severe cold waves stopped migration short. The 

 early males migrated at markedly higher temperatures, an average 

 of 50° F., than did the later males, which migrated at an average of 

 43° F. High temperatures in December, January, and early Feb- 

 ruary never brought a flight, so it is clear that migration was de- 

 pendent on both increasing day-length and rising temperature. 

 Fifty-seven migration dates for 22 banded males were obtained; 



5 birds came consistently early and 6 consistently late, while the 

 others varied in different years depending both on the weather and 

 on their ages, older birds coming earlier than yoimger ones. 



Territory. — The holding of territory is a fundamental trait with 

 these song sparrows, enforced by innate behavior patterns con- 

 sisting of song, display and fighting. This territoriality is essential 

 for the undistrubed carrying out of the reproductive cycle (Nice, 

 1939). Although highly territorial for over half the year, and in- 

 clined, if a resident, to remain on or near his territory permanently, 

 yet in fall and winter the male becomes somewhat social, particularly 

 in times of severe cold and snow. Occasionally females hold terri- 

 tory for themselves; sometimes one helps defend the male's bound- 

 aries; sometimes females ignore the boundaries established by males. 

 Male and female song sparrows were recorded as driving from their 

 territories their own and 21 other species, ranging in weight from 



6 to 42 or even 50 grams. (The song sparrow's own weight averages 

 22 grams.) Yet several of these species nested among the song 

 sparrows. 



Some male song sparrows keep the same territories year after year, 

 while others make slight changes. Females returned to their former 

 nesting territories in 20 of 54 cases, settled next door almost as often, 

 and in 19 instances settled at distances of from 100 to 800 yards. 

 Twenty- two males banded in the nest took up territories from 100 

 yards to nearly a mile from their birth places, while 12 females banded 

 in the nest settled from 50 yards to nearly a mile from their birth- 

 places. The minimum size of a territory was some 2000 square meters 

 (K acre), the average size in a region well filled with song sparrows 

 about 2700 square meters (% acre), and the maximum size about 

 6000 square meters (1% acres). In years of low population density, 

 territory size was somewhat larger. 



