Concord, Mass.
1903.
October &
November 
(No. 9)
  On the evening of November 3rd another novel and exceedingly
weird and startling sound was heard in the woods near the
farm house, just after sunset by E. H. Forbush, about half-past
seven o'clock by Gilbert and me. It was a loud, prolonged,
gasping shriek beginning at about the middle of the musical
scale and rising in pitch to the end. Forbush compared it
not inaptly to a siren whistle but it was less loud of course
and somewhat more husky in tone. On the following evening,
not long after sunset, I heard it again among some dense pines
near the same place (in Barrett Run). Hurrying towards the spot
I was soon almost beneath the bird but I could not see it.
After repeating its unearthly shriek five or six times it gradually
changed the cry to the low, tremulous wail of a Screech Owl.
The intergrading utterances were at least four or five in number
and the transition from the shriek to the wail was so obvious
as to convince me, as well as Forbush and Gilbert who were
with me at the time, that the "Owl with the siren whistle",
as we had dubbed the bird the evening before, was simply a 
Megascops asio with a novel and most interesting vocal
accomplishment. After this I repeatedly heard it shrieking,
as well as wailing, sometimes in the middle of the night in
the elms close to the house. On these as well as all the
previous occasions I noticed that the bird never shrieked
oftener than once every two or three minutes, a truly remarkable
fact for when engaged in wailing, or giving the low, rolling
call common to all the members of its race, it was, like all of
them, rarely silent for more than five or six seconds at a
time. I never interpreted either the wail or the rolling call
between the shrieks nor did I ever hear it utter all three
of these sounds on any occasion save that of the
evening of November 14th.