THE MIGRATION OF INLAND BIRDS. 189 



from some tall cedar or tangled brier-patch breaks the dead silence, 

 and we mark the arrival of the first spring songster of its kind. Did 

 it reach us at sunset, and, resting a few hours, then announce its pres- 

 ence with its cheery song ? 



Both by day and by night, it may be, they come, but why at all 

 by night, if so, must ever be a great mystery in the strange habit of 

 migration. 



Let us next study our birds during the autumn. 



A careful examination of the many notes, jotted down at irregular 

 intervals, during the months of September, October, and November, 

 with respect to the departure south of such of our birds as are sum- 

 mer residents, and of some that, having passed the summer in regions 

 far to the north, are now, likewise, seeking their accustomed winter- 

 quarters, indicates a similar apparent regularity in the southward 

 movements of our birds as in spring, and at the same time an actual 

 degree of variation in the dates of departure exceeding the irregular- 

 ity of the dates of arrival. 



If we consider the several circumstances that would necessarily 

 influence their migratory movements, this actual irregularity, in 

 autumn, is just what should be expected; but in the spring, as every 

 bird returns to its own home and former nest, if possible, they will 

 not linger on the way, as they know too well the length of the jour- 

 ney, and the coming duties of incubation speed them on, and we 

 wonder why they are not more regular in their movements. In autumn, 

 all this is changed. Now nothing need hurry them, and, so long as 

 they find an abundance of food, they leisurely move along, just keep- 

 ing ahead, as it seems, of the chilling frosts of the coming winter, 

 which they can easily endure, but which robs them of the food they 

 must have. This is especially true of insect-eating birds. Considered 

 in this light, we are not surprised to find, then, as a rule, that the 

 warblers, swallows, and such other birds as depend wholly upon in- 

 sects for their sustenance, leave more promptly and in larger numbers, 

 at one time, than do granivorous birds, and those that can subsist on 

 seeds, while they consume insects so long as they can find them. 



The weather, both during September and October, is exceedingly 

 variable, and this fact causes the southward movements of the migi-a- 

 tory, insect-eating birds equally so, inasmuch as these birds are not 

 larvae-hunting species, but depend upon insects that can be caught 

 upon the wing, or are to be found resting upon the leaves and twigs 

 of the trees; therefore, just so long as the heavy white frosts are 

 delayed, these insectivorous birds will linger with us. Up to a cer- 

 tain date, about October 1st on the average, these birds largely in- 

 crease in numbers, consequent upon the daily accession of those from 

 the north, and after the maximum is reached (October 1st or earlier, 

 in accordance with the weather), their number steadily decreases, un- 

 til but a few stragglers remain. 



