146 Observations on Periodical Birds. 
to suppose that the summer birds can become 
torpid with an increased or an increasing tem- 
perature: or that they can change their fea- 
thers in sucha state, when the organs of secre- 
tion are known barely to perform their several 
offices: or that under such circumstances, 
scarcely more than one fourth of those birds 
that withdraw in autumn, should re-appear 
in spring, though the same birds almost 
constantly return to the same haunts: these 
suppositions, I repeat, are manifestly absurd, 
therefore the summer birds must migrate. 
Writers in treating of the periodical birds, 
have confined their observations, almost ex- 
clusively, to the various species of swallow; 
neglecting, in a great measure, the short- 
winged summer birds, which seem to be the 
least qualified for migration; and the pe- 
riodical winter birds, which furnish some of 
the strongest arguments in support of it. 
If the periodical winter birds, do not leave 
this country in spring, they must stay with 
us the year through: yet it is in the highest 
degree improbable, that woodcocks, jack 
snipes, mountain finches, and the numerous 
flocks of redwings and fieldfares that are seen 
in winter, should remain here during the 
summer months, and yet elude the observa- 
tion of ornithologists. The redwing is ge- 
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