Concord, Mass.
1903.
October &
November
(No 4)
  Crow blackbirds were seen migrating in large flocks on two
occasions. On the first of these I counted flying
towards the S.W. about 8 A.M. at a height of fully 1000 feet
above the earth. The other flock was observed just before sunset
on the evening of by Mr. Forbush and Howard Mc.Clair
who were engaged at the time in shingling the roof of a shed
at the Ritchie place. They both agreed that the birds, flying S.W.
at a height of several hundred feet, formed a continuous line or 
belt extending N.W. and S.E. or at right angles with their course
and stretching uninterruptedly as far as the eye could reach in
both directions, or for a distance of at least two miles. Forbush
said that he would not attempt to estimate but that he had
certainly never had so many birds of any kind in sight at once
before; Mc.Clair that "there must have been tens of thousands."
The line although unbroken was not everywhere single for in
many places there were double or triple ranks. Mr. Forbush
did not fully identify these birds but he thinks that
most of them were Crow Blackbirds although a small bunch,
which passed directly over him, lower down than the rest, was
apparently composed of Rusties which he recognized
by their notes and flight. The birds composing the amazingly long line
above flew steadily & evenly like Crow Blackbirds, but they
were too high for their boat tails to be distinguished. My
own idea is that they must have been Crow Blackbirds for
I have never known Rusties to migrate in very large
flocks. The annual flights of Quiscalus aeneus, which
we note every autumn at Concord, must come from rather
far to the northward. As a rule the birds pass, as they
did on the two occasions just mentioned, without stopping
to rest or feed in our neighborhood. Our local birds must 
depart somewhat earlier in the season.
Extraordinary migration of Crow-blackbird