1898] Bird Migration. 41 



water Shales, and the " Tar Sands " as one formation. This is a 

 marine formation, stratigraphically equivalent to the Dakota, the 

 fossils of which are practically the same throughout, and although 

 no corres[)onding marine fossils are known elsewhere in the 

 west, it appears to represent the marine conditions of the 

 Dakota Period. 



BIRD MIGRATION 1898. 



To the Editor of the Naturalist. 



The bird migration of the present spring, so far as it has 

 yet progressed, has developed some features which I think are 

 worthy of note. 



The usual course of the migratory movement of the earlier 

 part of the season may be described somewhat as follows : — As 

 soon as the March thaw has made sufficient progress to lay bare 

 a good part of the surface of the ground — say one-third — the 

 earliest of the true migrants begin to arrive. The song sparrow 

 and the robin are generally first, but they are followed in 

 three or four days, if not actually accompanied, by the bluebird 

 and several species of grackle. These are all ground-feeders, at 

 least at this time, for the winter visitants and the storms have 

 stripped the trees and shrubs of the last remains of last 

 season's fruits and seeds, so that the only food supply is 

 that which has lain all winter under the snow. Should 

 the warmth of the .sun bring out a few winged insects 

 in sheltered nooks, an odd phoebe will be found looking 

 after them ; but he may be considered a venturesome pioneer, 

 while all the other flycatching birds still linger in their winter 

 homes. Probably every individual of these first arrivals will 

 have spent, at least the latter part of the winter in Southern 

 New York or Pennsylvania, for the first two si)ecies regularly 

 winter there while the others, though retiring somewhat further 

 south at the commencement of the cold weather, begin to push 

 northward early in February. /%\ 



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