Hello Dennis and Twetters,

Just a brief comment on cowbirds at McChord. I have been surprised at the
relative low levels of cowbird success in nest that we have monitored over
the past for years. I don't have the figures at my finger tips but overall
there has been only small percentage of nest with cowbird eggs in them.
Most of these nest are for birds like Junco, White-crowned Sparrow, Yellow
Warbler, Common Yellowthroat and the likes. All nesters in shrubs or on
the ground. A good number of the nest if the nest with cowbird eggs failed
or were abandoned. I found several nest where the cowbird egg was rejected
from the nest (all White-crowned Sparrows if my memory is correct), or the
nest was abandoned (Orange-crowned Warbler and Yellow Warbler). I found it
interesting that I never saw any Yellow Warbler nest that were piled on
top of each other. The nest was either abandoned or the chicks fledged.

Last year, we color-banded cowbirds to see what the local population might
be like. Our point counts detected cowbirds often. Just from looking at
point counts we thought that cowbirds were very abundant. However,
color-banding showed that we were seeing the same individuals over and
over. I estimated the local population to be between 8-12 birds total. I
thought that this number of birds roughly corresonded with the ratio of
eggs found in nest.

In South Carolina, I found cowbird eggs in 100% of Blue Grosbeak nest and
nearly that in some other species. I was looking for similar numbers at
McChord but it just did not turn out to be the case.

All this is not to say that I don't think cowbirds are a problem, I think
that they are. They are just not as big of a problem as I was expecting. A
bigger problem that I was not expecting was the Cross-base Highway. It
will probably do far more damage than the cowbirds.

My two cents,

Russell Rogers
Olympia WA