Concord, Mass.
1910 
June 7
[June 7, 1901]

Cow-birds

  On June 4 I saw three Cow-birds, 2 males & 1 female,
flitting through our orchard apparently looking for birds' nests.
There were three together there again this morning but with
the proportion of sexes revised ie there were 2 females and
only one male. The sat perched close together on a dead branch
for several minutes. Shortly after this I saw a [female], presumably
one of this trio, fly straight to a last year's nest of Vireo
flavifrons in one of our large elms. Alighting on its rim
she looked down into it intently and then flew away in
apparent disgust closely pursued by a female Redstart and
one or two other small birds that I could not identify.
They made a rather loud outcry such as would have been
the case had they been disturbed by the presence of a Jay or
Hawk. This seemed to me to indicate plainly that they
were quite aware of the indirect danger due to the presence
of the Cow-bird. I had not known before that her real character
is thus known to any of the birds she imposes on.