I found a small colony in Portland off North Gertz Road in about 1967 (I would
have to look up the date to be sure) within a hundred yards or so from where
the Portland birds were found years later. Their presence in Portland was a
big surprise. I suspect that they have been scattered colonies in northern
Oregon for a long time. There were very few birders in Oregon who could
identify many species even into the 1980s. In addition, field guides just
weren't very good.
Jeff Gilligan
On Mar 21, 2016, at 8:07 AM, 5hats@xxxxxxxx wrote:
Paul Sullivan's recent discovery of Tricolored Blackbirds in Gilliam County
prompted this post.
Prior to about 1980 the only known breeding locations for the species
were located in southern Oregon, primarily in Klamath and Jackson Counties.
Then sometimes around the early 1980's ( I don't have the exact date) a small
colony of them was discovered near Camp Hancock in southeastern Wasco County.
This spot is approximately one hundred seventy miles north of any breeding
location known to exist at that time. Within a very few subsequent years
other colonies were located near Hermiston in Umatilla County, Prineville in
Crook County, and at the Painted Hills Unit of the John Day Fossil Beds near
Mitchell, Wheeler County. There were also reports of a few birds near
Portland, Multnomah County, as well as in other scattered locations in the
north-central part of the state, where they seem now to have become regular.
The species has been recorded in Wasco, Sherman, Gilliam, Morrow, Umatilla,
Wheeler, and Crook Counties, with breeding reported in most of them.
It is speculation on my part, but I have long suspected that this spread
of the species into north-central Oregon was not the result of a range
expansion from southern Oregon, but rather a dispersal of birds from a
previously unknown breeding location closer to the area, and there is at
least some data to support the hypothesis. About twenty miles northeast of
Madras, very near the now defunct town of Willowdale, there used to be a
large cattail marsh on the west side of US highway 97. This particular
marsh was a couple of miles long, probably at least a mile wide, and
completely inaccessible. The cattails which grew in the marsh were higher
than a man's head, and there were no elevated places along the highway from
which a person could see out over the marsh. It is not at all unreasonable
to think that an inaccessible marsh of that size could have hosted a colony
of Tricolored Blackbirds without anyone ever detecting their presence. I
believe it was in 1979 that the marsh was drained and converted to cropland.
My records show that on June 9,1980 at Willowdale I saw a Sora at dawn in
what had formerly been a cattail marsh. It was the year after that marsh was
drained that the Tricolored Blackbirds were reported at Camp Hancock, which
is only a few miles to the northeast, and subsequently began to be reported
in other spots in the north-central portion of the state.
If Tricolored Blackbirds did once have a colony at Willowdale (and it
cannot be proved they did), it is interesting for several reasons. (1) It
means that the species had a breeding location in Oregon, unknown to birders,
nearly two hundred miles north of any previously known breeding location. (2)
It explains the sudden and surprising spread of the species into the
north-central portion of the state. (3) it suggests that the species is
perhaps more adaptable than previously thought. Tricolored Blackbird is
known to be a colonial nester, most colonies being made up of numerous pairs
or females and polygamous males. Most of the colonies which now exist in
north-central Oregon are relatively small. I never counted birds, but the
largest colony I have observed was the one which nested for a while between
Prineville and O'Brien. It had maybe a couple of hundred birds. The one I
saw near Hermiston had perhaps half that many. The one at the Painted Hills
Unit of the John Day Fossil beds I do not think had over twenty birds total.
One of the thing which makes tracking this species a bit difficult is
that their breeding colonies in the north-central part of the state seem to
shift locations from time to time. There are undoubtedly people who know far
more about the numbers of birds and the locations in which they breed than I
do. I am only piecing together what little data I have from occasional trips
to the area, and none of it has hard documentation in terms of numbers.
However the continuing reports of this species in that section of the state
suggests it has successfully colonized a new area, and is continuing to
expand its range within that area. I present this post to give this apparent
range expansion a bit of historical perspective.
I might also add that Paul's recent discovery of the species in Gilliam
is not unprecedented. Once previously he found a small breeding colony of
them along Rock Creek near the bottom of Wolf Hollow Road south of Olex. I
have looked there several times since and seen only Red-winged Blackbirds.
I would encourage those who know more about the presence and spread of
this species into north-central Oregon to contribute to this thread.
Darrel
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