Intermixing alters NSO equation

Daniel B. Wheeler dwheeler at
Mon Jul 2 23:27:16 EST 2001

>From The Oregonian, June 7, 2001, p C1

Intermixing alters owl equation
California birds moving north are interbreeding with Oregon's
protected populations, raising new questions about protection

	More Californians are moving to Oregon, but these immigrants are
California spotted owls infiltrating Northwest forests and mixing with
the threatened northern spotted owl, researchers say.
	Perplexed scientists don't know why the scarcer California owls,
native to the Sierra Nevada and Southern California mountains, are
heading north. Nor do they know how interbreeding might dilute the
genes of their northern relative. Decline of the northern owl halted
much of the logging in Northwest public forests in the past decade.
	If the federal government eventually awards the California owl the
same Endangered Species Act safeguards the northern spotted owl has,
as conservation groups have asked, the Northwest may find a second
protected spotted owl in its forests.
	New studies published in the June edition of the journal Conservation
Genetics suggest the owls remain distinguishable through their DNA,
and scientists say some mixing between subspecies is normal. But the
findings could revive an argument first raised in 1915, but since
rejected, that the owls are similar enough to be combined into a
single subspecies that would be more widespread and abundant than
either of the separate owls by themselves.
	When scientists examined the genetic makeup of birds they thought
were northern spotted owls from as far north as the Siuslaw National
Forest west of Corvallis, about 13 percent turned out to be California
spotted owls. If that proportion carries through the rest of the
nearly 10,000 northern spotted owls in the Northwest, about 1,000 may
actually belong to a different subspecies.
	"It's somewhat confusing because we're not seeing owls here that look
very different from northern spotted owls," said Eric Forsman, a
spotted owl biologist with the U.S. Forest Service in Corvallis and a
co-author of the studies.
	Researchers do not know when California spotted owls began moving
north, but they suspect it's a relatively recent shift because the
genes of the two subspecies have not fully mixed.
	Scientists launched the new genetic studies so they could more
clearly gauge the differences among three subspecies of spotted owls:
northern, California and Mexican. They found the Mexican spotted owl
of the Four Corners states clearly distinct, but they had a more
difficult time identifying the other two subspecies. Their ranges
turned out to overlap far more than anyone had expected.
	When scientists grouped owls based on their genetic similarity to
other owls from a certain area, almost as many California spotted owls
appeared to belong in the Olympics, Cascades, Coast Range and Klamath
region of Oregon and Washington as in California.
	"We were not expecting there to be this much mixing," Said Susan
Haig, a U.S. Geological Survey conservation genetics specialist in
Corvallis who was lead author of the new studies.
	Although California spotted owls are clearly moving north into
Oregon, she said there is no sign that the northern spotted owl is
moving south into California. That could be because logging in
California's mountains might have disturbed the habitat of the
estimated 2,000 to 3,000 California spotted owls more than it has the
range of the more numerous northern spotted owl in the Northwest.
	Both species rely on relatively undisturbed, mature forest.
	"If things aren't so hot in California, the California owls may be
going out of their range to a new area that can provide some qualities
they're not getting at home," said Patricia Foulk of the U.S. Fish and
Wildlife Service in Sacramento, Calif.
	Although the northern spotted owl is listed by the federal government
as threatened, the California spotted owl is not. Conservation groups
have petitioned the Fish and Wildlife Service to list the California
subspecies. The agency ruled that a listing may be warranted but has
put any action on hold for budget reasons.
	In other cases where two different animals closely resemble each
other, federal authorities have designated both as threatened or
endangered so a protected species is not accidentally disturbed when
it's mistaken for an unprotected species.
	Biologists said their studies also showed that the populations of all
spotted owls contain little genetic diversity overall, making them
even more sensitive to the slicing and dicing of their habitat by
development than first thought.
	"As that happens, the populations become even more isolated," Forsman
said. "The populations in both areas are not doing very well, and the
fact that they're missing doesn't change that."

Comment by poster: Interesting premise: are new hybrids of endangered
species protected under ESA? Would/should/are they a "new" species? Is
it possible a barred owl/NSO is more likely to survive under today's
new environmental conditions? Is this a case of natural adaptation
(evolution) or just survival of a species' traits at all costs?

Daniel B. Wheeler

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