Of the various factors limiting the abundance of birds, particularly
the smaller species, storms are the most potent. Special sufferers
are those birds that in crossing broad stretches of water are forced
by a storm down within reach of the waves. Such a catastrophe was
once seen from the deck of a vessel in the Gulf of Mexico, 30 miles
off the mouth of the Mississippi River. Great numbers of migrating
birds, chiefly warblers, had accomplished nearly 95 percent of
their long flight and were nearing land when, caught by a norther,
against which they were unable to contend, hundreds were forced into
the waters of the Gulf and drowned. On another occasion, on Lake
Michigan, a severe storm, coming up at a time when large numbers
of migratory birds were crossing, forced numerous victims into the
waves. During the fall migration of 1906, when thousands of birds
were crossing Lake Huron, a sudden drop in temperature, accompanied
by a heavy snowfall, resulted in the death of incredible numbers.
Literally thousands were forced into the water and subsequently cast
up along the beaches, where in places their bodies were piled in
windrows. On one section of the beach the dead birds were estimated
at 1,000 per mile, and at another point at five times that number.
Most of them were species that rank among our most desirable birds as
destroyers of insects and weed seeds, including slate-colored juncos,
tree sparrows, white-throated sparrows, swamp sparrows, winter wrens,
and golden-crowned kinglets, together with many brown creepers,
hermit thrushes, warblers, vireos, and others.
Of all species of North American birds, the Lapland longspur
(_Calcarius lapponicus_) seems to be the most frequent victim of
mass destruction from storms. These birds sometimes congregate in
enormous numbers where grass or weed seed is abundant. Almost every
winter brings in reports of their death by thousands somewhere in the
Middle West. While migrating northward at night they have encountered
blinding storms of wet, clinging snow, which have so bewildered
them that they have flown into various obstructions, or have sunk
to the ground and perished of exposure and exhaustion. In 1907 an
experienced ornithologist estimated that 750,000 longspurs were lying
dead on the ice of two lakes in Minnesota, each about 1 square mile
in extent, and dead birds were reported in greater or less abundance
on this occasion over an area of more than 1,500 square miles. The
heaviest mortality occurred in towns, where, bewildered by the
darkness and the heavy falling snow, some of the birds congregating
in great numbers, flew against various obstacles and were killed or
stunned, while many others fell to the ground exhausted. Similar
catastrophes have been reported from eastern Colorado, Nebraska, and
North Dakota.
During the early part of June 1927, a hailstorm of exceptional
severity in and around Denver, Colo., killed large numbers of robins,
meadow larks, sparrows, and others. The lawns of parks were strewn
with the bodies of these birds, and many lay dead in their nests
where they were covering their eggs or young when the storm broke.