Dear Anthony,

Though not on "obol" a friend of mine showed me your email
question and I thought that I might be able to reply
[Please be forwarned that my response is lengthy!]. I work
for the Oregon Cooperative Wildlife Research Unit and have
been studying northern spotted owls for seven years now as a
project leader of the Central Cascades NSO Demography study
located on the Willamette National Forest.

It is a common misperception that spotted owls need
pristine old-growth forest in order to exist. However, it
is also becoming a common misperception that they DON'T need
old-growth forests to exist--let me explain.

The confusion is largely due to our inability to describe
the wide range of forest characteristics with the two words
"second-growth" and "old-growth". By applying one of these
two terms to the many different forest conditions present
within the range of the northern spotted owl we grossly
fail to capture this range of conditions.

What northern spotted owls do seem to need are forests
with structural complexity. Such forests tend to provide
the food items, nesting structures, thermal regulatory
conditions, escape cover, etc.--in sum, all of the life
history requirements for the species. When a habitat meets
all of these conditions in a most efficient manner we can
say that that habitat is "optimum" for that species (a term
applied to old-growth in the Interagency Scientific
Report for the NSO). All current evidence overwhelmingly
suggests that the "old-growth" forests within the range of
the owl provide for all of its life-history needs in this
"optimal" way.

Let me reemphasize that forest structure (and all of the
things that are associated with that structure) is the key
element to spotted owl habitat needs. It should not be
surprising to find spotted owls travelling through, foraging
in, or even nesting in forests that provide complex
structure but that would not qualify as pristine
"old-growth" by human definition. A straightforward
example of this can be found in northern California and
southern Oregon where redwoods occur.

If you clear-cut an
old-growth redwood stand and then leave it alone for as
little as 30 years you might have a good chance of finding a
spotted owl nest there. The resulting 30 year-old
forest is remarkably structurally complex due to
several factors. First, redwoods sprout from the
stump on their own and begin growth rapidly.
Second, the incredible growth-rate results in very
large trees very fast. Third, the influence of
other associated species of trees growing along with
redwoods contribute to the vertical structure of the stand.
Lastly, in that region owl prey items (esp. woodrat spp.)
are in high abundance and density. These facts led to
consideration of exempting the owl populations in this
region from receiving designation as "Threatened" during the
status review of the NSO. However, it was felt that the
owls in this region were an important element to the
population as whole, since owls were doing so poorly in
other parts of their range (e.g. Oregon Coast range).

In contrast, to illustrate how different forest-types
provide different conditions: if you went to the central
cascades of Oregon and clear-cut an old-growth douglas-fir
stand and let it sit for 30 years you would have all of the
structural complexity of a corn field. In fact, you might
have to wait as long as 130 or 230 years to find a spotted
owl nest there!

Another important illustration should be made. In the
non-redwood forests occupied by the species you can find
nesting pairs in what would be considered "second-growth".
For example, in the Roseburg and Medford vicinities where
complex fire regimes and different logging practices
(extensive use of selective harvest techniques) have taken
place it is common to find owls in non-pristine old-growth
forests and even in forests that would better be called
"second-growth". However, these "second-growth" areas tend
to be somewhat different from the images of the corn-field
like plantations that the term "second-growth" conjures
up in our minds and is usually applied to. Nearly without
exception, owl nests located in "second-growth" are located
in pockets of forest that contain some residual elements or
characteristics from the old-growth forest that once
occupied the area (i.e. at least a few large, standing dead
and/or live trees, and usually some large logs and woody
debris on the forest floor)--STRUCTURAL COMPLEXITY! Thus,
whereas the stand in general might be only 40 years of age,
the portions selected by the owls retain some "older"
characteristics.

To summarize: while it may be MOSTLY ACCURATE to say that
"all old-growth (coniferous forest within the range of the
owl) is spotted owl habitat", it is not accurate to say that
"all spotted owl habitat is old-growth". Further, n.
spotted owls will use second-growth forests for 1) dispersal
habitat: as young as 30 yrs. [e.g. Douglas-fir/western
hemlock in Oregon Cascades], 2) as foraging habitat: forests
of approx. age 30-80 [e.g. Douglas-fir/western hemlock in
Oregon Cascades], and 3) as nesting habitat: regenerating
redwood forest, young forests regenerating after fire or
selective harvest where residual components (i.e. standing
large trees and downed logs and woody) are present [many
areas throughout Oregon and Washington].

I hope this lengthy description was helpful. Please feel
free to respond or contact me further. Please note however,
that I only check my email once every two weeks or so.

Sincerely,

Keith Swindle


-Don Baccus-