THE NIGHT CRY OF THE REDWING. 255
between, the valley falls to about 630. This short walk, when
Redwings are calling, proves easily that the birds are not flying
in a straight (i.e., horizontal) line—they may be fifty feet over-
head as I cross the bottom of the valley, and yet the same
voices may still be overhead when I reach the top of the hill.
Within six miles or so there are many higher hills, reaching up
to almost 2,000 feet. The Greenfield valley, for instance, is
a cul-de-sac open only at one end ; the other sides are walled
in by a curved plateau 1,600 feet and more above sea level. All
around are wide moors, devoid of grass or shrubs, and totally
unsuitable for Redwings by day. These hills are crossed by high-
roads, some of them reaching an elevation of 1,600 feet, then
dropping to about 600 at the bottom of the valley. On a good
night the calls of the Redwing are frequently heard in this
valley below the level of the hill summits ; and I have stood on
a steep hill and heard birds passing below my level, and within
a few seconds noticed other calls perhaps hundreds of feet over-
head.
The evidence of my ears often suggested that these travellers
were not all passing in the same direction, and in 1921 I decided
to make observations through a prismatic field-glass focused
against a moonlit cloud. I quote from my note-book of the
17th October (1921) :—" To-night many Redwings flying over.
Moon with clouds. At 8.45, watching sky with glass, distinctly
saw a Thrush-like bird flying across at right angles from N.E.
to S.W. A few seconds later another in precisely the opposite
direction ; and, at 9.15, a third flew ' up ' the field of the glass
—E. to W. or thereabouts. At 8.30 heard 3 Redwings in 3
seconds ; and some dozens during the night." Two observa-
tions may be added here. On that night I distinctly heard the
voices of Song Thrushes—a few in number. And, from 8.30
to about 9.30 (while my visual observations were being made)
I heard no Redwings.
I find that watching the sky through a field-glass is tiring
work. Perhaps some reader may be able to suggest or to try
a better method of visual observation. It seems to me that
further observations may prove that I am right in thinking that
these nocturnal Redwings are not migrants travelling from
place to place, but that they are wandering aimlessly in the
dark air, or perhaps in flocks flying around in regular evolutions.