THE MIGRATION OF NORTH AMERICAN BIRDS 29 
Birds occupying the most southern part of the general range are 
almost nonmigratory, residing throughout the year in Florida, while 
those breeding as far north as Newfoundland go to the West Indies 
for the winter, thus passing directly over the home of their southern 
relatives. 
The palm warbler (Dendroica palmarum), which breeds from Nova 
Scotia and Maine west and northwest to southern Mackenzie, has 
been separated into two subspecies. Those breeding in the interior 
of Canada (2. p. palmarum) make a 3,000-mile journey from Great 
Slave Lake to Cuba, 
passing through the 
Gulf States early in 
October. After the 
bulk have passed, the 
palm warblers from 
the Northeastern 
States and Provinces 
(D. p. hypochrysea) 
drift slowly into the 
Gulf coast region, 
where they remain for 
the winter. Their 
migratory journey is 
about half as long as 
that of the north- 
western subspecies. 
There is no invaria- 
bie law governing the 
distance of migration, 
although in general it 
is found that where a 
species has an exten- 
sive range, the sub- 
species that breed far- 
thest north go far- 
thest south to spend 
the winter. 
FALL FLIGHTS NOT FAR B4774AM 
SOUTH OF BREEDING FIGURE 12.—Migration of Pacific-coast forms of the fox sparrow. The 
RANGES breeding ranges of the different races are encircled by solid lines, 
while the winter ranges are dotted. The numbers indicate the areas 
S h : used by the different subspecies, as follows: 1, Shumagin fox sparrow; 
ome other species 2 Kodiak Ls SUS 3, Valdez fox sparrow; 4, Yakutat fox sparrow; 
= r 1 5, Townsend fox sparrow; 6, sooty fox sparrow. (After Swarth; cour- 
that hav e extensive tesy of the Museum of Vertebrate Zoology, University of California.) 
summer ranges, for in- 
stance, the pine warbler (Dendroica pinus), rock wren (Salpinctes obsole- 
tus), field sparrow (Spizella pusilla), loggerhead shrike (Lanius ludovicia- 
nus), and black-headed grosbeak (Hedymeles melanocephalus), are 
found to concentrate during the winter season in the southern part 
of the breeding range, or to occupy additional territory that is only 
a short distance farther south. The entire species may thus be con- 
fined within a restricted area for the period of winter, and then, with 
the return of warmer weather, spreads out to reoccupy the full range. 
