Figure 28.--A banded belted kingfisher, one of about 2,000,000 birds that have been marked with Biological Survey bands.] =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 delinite 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.