The sudden rise or fall in the migration may also be seen at a glance. May 9, 1899, for example, only 16 different species were observed and May 10 the record was 40. Similarly, in 1901, the number of species seen May 17 dropped from 45 to 15 in three days.
A chart showing the number of different kinds of birds seen in LINCOLN PARK during the HEIGHT OF THE MIGRATION
Note to Key.
In response to many demands, the following simple field-key has been devised, to the end that the beginner may be aided in learning to observe correctly those points about a bird that appear most conspicuous in the field or which are particularly distinctive.
Technical analyses and measurements have not been employed, but instead, the birds are roughly placed in three groups according to size, the Robin and English Sparrow marking respectively the 10-inch and 6-inch lines of division.
The first part of the key deals with general differences in color and markings, while the second seeks to emphasize the most noteworthy special points which distinguish the different species. Incidentally a few striking peculiarities of bill, wings and tail have been included.
It will readily be seen that a key embracing so little cannot do more than reduce wild guessing to a few reasonable chances in identifying a strange bird. Some practice is of course necessary to enable the student to use the key readily. Its helpfulness will largely depend upon accuracy of observation and a careful application of the points which it suggests.
Shore and water birds have been omitted—first, in order to keep the key as simple as possible; second, because quite full descriptions of these birds are given in the “Particular Hints;” and, third, for the reason that beginners, as a rule, meet with far better success by becoming familiar with the common land birds before attempting the study of water and shore birds.