THE MIGRATION OF BIRDS. 347 
was ice upon the ponds, five inches in thickness. The cranes had 
not escaped a day too soon. 
Many birds prefer to migrate during peculiar conditions of 
weather. The crows almost always move north against a high 
' March wind. A long rainstorm with heavy winds, in the early 
part of May, is almost sure to be followed, as soon as it has 
cleared away, by a great influx of warblers; and I have noticed 
that the migrating hawks often appear in much greater numbers 
than usual under the same circumstances. In May, 1865, a long 
northeast storm, clearing up in the evening of the second day, was 
followed by an extraordinary flight of hawks. Spending the day 
in the woods, I was astonished at the number, both of individuals 
and species. They passed overhead, just above the tree-tops, every 
moment; sometimes singly, sometimes in pairs, and at times in 
small parties of five or ten or even twenty or thirty. Ata low 
estimation, I saw a thousand during the morning; and have no. 
doubt that I might have seen ten times as many had I been in the 
open fields, instead of dense woods. The red-tailed, sharp-shinned, 
Cooper’s and broad-winged species were the most common; but 
half a dozen other species were observed, including a golden eagle, 
the only one I ever saw in that locality. All were pursuing the 
same course—northeast—and all flew at nearly the same eleva- 
tion, close to the tops of the trees, as if to avoid the strong. head- 
wind as much as possible. Although I had nothing larger than No. 
10 with me, such alluring shots were constantly presenting them- 
selves, that I was tempted to fire a score of times or more, without ` 
loosening a feather. Had I been supplied with the proper ammu- 
nition, I might have secured fifty specimens that day. Other in- 
stances are afforded by the hummingbird, who journeys only on 
the brightest, sunniest days; and the snow bunting, whose pre- 
dilection for travelling with snow storms, has gained for him, 
among the Swedes, the name of ‘‘bad-weather bird.” 
But although we may assign many reasons for the migration of 
birds, there is much about them that is seemingly inexplicable. 
It is hard to say, for instance, why the black-throated bunting 
should delay his coming till May, when his relative, the chipping 
sparrow arrives a month earlier, and the song sparrow a month 
or six weeks earlier still; although neither is equipped with stouter 
bills or forms, or are apparently better adapted to withstand the 
cold. Or it would be puzzling to tell why Aiken’s snowbird, which 
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