THE NATURAL HISTORY SURVEY. 23 



MIGRATION OF THE BIRDS. 



Of the migration of the birds of our region, depending as 

 it does almost entirely upon the weather conditions, little more 

 can be said beyond the individual reports of arrival and de- 

 parture. This is especially true of the insect-feeding birds 

 which are very sensitive and deeply feel all sudden changes of 

 temperature. They are "perfect barometers in that respect." 

 Some years the migration of the birds is greatly impeded by 

 severe or variable weather, and in these years quite large numbers 

 of migrant birds have been destroyed by sudden changes to cold 

 and stormy weather from a fair and warmer atmosphere, which 

 has attracted the birds. The interesting Bluebirds appear usually 

 about the middle of March, but it was my pleasure to observe 

 one as early as February 22, and Mr. Benjamin T. Gault heard 

 one calling at Glen EUyn, not far west of Chicago, on February 

 28, 1896. 



The height of migration of the Passeres in our area seems 

 to be from the first to the tenth of May in the spring, and about 

 the middle of September in the fall. It will be of interest to 

 note the height of migration during eight years, from 1893 to 

 1900, as recorded by Mr. Gault at Glen Ellyn, Illinois. His 

 record is as follows, and is the result of his observations of the 

 vireos, the warblers, and the smaller thrushes used as an index 

 or basis to mark the height of the spring migration season: 



1893 May 12 to 14 inclusive 



1894 May 14 to 16 inclusive 



1895 May 19 to 23 inclusive 



1896 May 6 to 12 inclusive 



1897 May 8 to 15 inclusive 



1898 May 13 to 20 inclusive 



1899 May II to 19 inclusive 



1900 May 15 to 19 inclusive 



The maritime birds straggle through our area in the spring 

 from April to June. It is a rather strange fact that late in May 

 and in June there may sometimes be seen large flocks of Red- 

 backed Sandpipers (Pelidna alpina sakhalina), Black-bellied 

 Plovers {Squatarola squatarola), the Knot or Robin Snipe 

 (Tringa canutus), the Least Sandpiper (Actodromas minutilla), 

 and the Semipalmated Sandpiper (Ereunetes pusillus) along the 

 shores of our smaller lakes. Whether these birds are simply 



