40 EXTENT OF MIGRATION 
September 20-30.—Herring Gull (May), Yellow-bellied Sapsucker 
(October 20-30), Junco (May 1-10), White-throated Sparrow (May 1-20), 
White-crowned Sparrow (October 15-30), Myrtle Warbler (May 5-20), 
Yellow Palm Warbler (October 15-30), Brown Creeper (April), Golden- 
crowned Kinglet (April), Ruby-crowned Kinglet (October 20-30), 
Winter Wren (April), Gray-cheeked Thrush (October 15-25). 
October 1-10.—Bronzed Grackle (December), Rusty Blackbird 
(December), Pipit (October 25-November 5), Hermit Thrush (Novem- 
ber). 
October 10-31.—Horned Lark (April), Pine Finch (April), Snow 
Bunting (March), Redpoll (April), Tree Sparrow (April), Fox Sparrow 
(November 25-December 10), Northern Shrike (April). 
November.—Pine Grosbeak, White-winged Crossbill, Red Cross- 
bill. 
The Extent of Migration—After this glimpse of the swing of the 
pendulum of migration, from a local point of view, we may extend our 
inquiry by following the birds to their winter quarters, with the object 
of learning where they go and the routes they travel. 
Generally speaking, the extent of a bird’s migration is related to 
the character of its food; insect-eating birds journey much farther 
than seed-eaters, many of which travel but a short distance south 
of their birthplace. There are, however, some marked exceptions to 
this statement. The Bobolink, for instance, is in part granivorous, 
but it winters south of the Amazon, while the Golden-crowned Kinglet 
is insectivorous and winters as far north as New England. Again, of 
two insectivorous birds, one, the Short-billed Marsh Wren, does not 
winter north of the Gulf or South Atlantic States, while the other, the 
Winter Wren, is found northward to New England in winter. Numer- 
ous similar instances might be cited, all indicating that some cause 
other than food has determined the extent of the journeys made by 
many migratory birds. It will be observed that of the species just 
mentioned, the Bobolink and Short-billed Marsh Wren are American 
types of austral origin, while the Golden-crowned Kinglet and Winter 
Wren are European types and of boreal origin. Further inquiry will 
show that among land-birds the migrants which go farthest south 
belong in the first class, while those which winter farthest north belong 
in the second class. It is not improbable, therefore, that the extent 
of a bird’s migrations may give some indication of its place of origin 
as a migrant. 
In the western states the migration of birds is not so pronounced 
as it is east of the Rocky Mountains, and the latitudinal movement 
is complicated by an altitudinal one. The migrants of this region, 
which winter south of the United States, pass this season largely in 
Mexico. Comparatively few land-birds go beyond Guatemala and 
practically none cross the Isthmus of Panama. 
In eastern North America, not only are migrants proportionally . 
more abundant, but their movements are more clearly defined, and 
