PROBLEMS OF MIGRATION
BANDING STUDIES
The study of living birds by the banding method, whereby great numbers of individuals are marked ([fig. 28]) with numbered aluminum leg rings, has come to be recognized as a most accurate means of ornithological research. Since 1920, banding work in North America has been under the direction of the Bureau of Biological Survey, in cooperation with the National Parks Branch of Canada. Every year volunteer cooperators, working under permit, place bands on thousands of birds, game and nongame, large and small, migratory and nonmigratory, each band carrying a serial number and the legend, NOTIFY BIOLOGICAL SURVEY, WASHINGTON, D. C., or on the smaller sizes, NOTIFY BIOL. SURV., WASH., D. C. When a banded bird is reported from a second locality, a definite fact relative to its movements becomes known, and a study of many cases of this nature develops more and more complete knowledge of the details of migration.
The records of banded birds are also yielding other pertinent information relative to their migrations, such as the exact dates of arrival and departure of individuals, the length of time that different birds pause on their migratory journeys to feed and rest, the relation between weather conditions and the starting times for migration, the rates of travel of individual birds, the degree of regularity with which birds return to the exact summer or winter quarters used in former years, and many other details that could be learned in no other manner. Banding stations that are operated systematically throughout the year, therefore, are supplying much information concerning the movements of migratory birds that heretofore could only be surmised.
MOVEMENTS OF RESIDENTS
Typical migration consists of definite movements that are repeated regularly year after year, and it is to these that the term is generally restricted. It is desirable, however, if only for purposes of comparison, that some account be taken of the movements of some other birds, which, while not typical, do possess some of the characteristics of true migration. Data on this subject are being collected through bird banding.
There are several species that are customarily grouped under the heading "permanent residents", the term implying that these birds do not travel but remain throughout the year in one locality. Among these are the cardinal, the tufted titmouse (Baeolophus bicolor), the wren tit (Chamaea fasciata), the Carolina wren, the house finch (Carpodacus mexicanus frontalis), the bobwhite (Colinus virginianus), the California quail (Lophortyx californica), and the ruffed grouse (Bonasa umbellus). Each species may be present constantly throughout the year, although in the northern part of the range there is probably a slight withdrawal of the breeding birds in winter. The individuals to be seen at that season, therefore, may not always be the same as those observed during the summer. It is certain, however, that these species do not regularly perform extensive journeys.
While the blue jay is disposed to be secretive, it is such a showy and noisy bird that is not likely to escape notice. In the vicinity of Washington, D. C., as in many other places, it is present the year round, but at the end of September or early in October when the weather is becoming cooler, troops of jays are sometimes seen working southward through the trees. A corresponding northward movement occurs again in May. This is unquestionably a migration to and from some winter range, but its extent or significance is not now known. Some light is being shed on the matter, however, through the records of banded birds, and these eventually will fill in a more perfect picture of the movements of this species. One jay, banded on September 14, 1923, at Waukegan, Ill., was killed at Peruque, Mo., on November 15 of the same year; another, banded at Winnetka, Ill., on June 16, 1925, was retaken at Sulphur Rock, Ark., the following December 10; a third, banded on May 6, 1925, at Whitten, Iowa, was recaptured at Decatur, Ark., on January 22, 1926. These three birds unquestionably had made a flight that had every appearance of being a true migration to winter quarters in Missouri and Arkansas.
The black-capped chickadee is apparently resident in many places, but occasionally in winter it invades the range of the southern Carolina chickadee (Penthestes carolinensis) and in northern Canada it is regularly a migrant.
In the coastal plain between Washington, D. C., and the Atlantic Ocean, the white-breasted nuthatch is usually absent during the summer, nesting at that season in the higher, or piedmont, country. Late in fall, however, it appears in fair abundance in the wooded bottoms, remaining at the lower levels until the following March or April.