Interesting notes: As many people know, the northern spotted owl is at the eye of a political hurricane. The old-growth forests of Washington, Oregon, and California provide timber jobs and support to many local communities. Most of these forests are found on federal lands, putting their management in the hands of politicians. The problem is clear, what is popular with one group of voters isn't necessarily popular with another group of voters. Some people want jobs and could care less about saving owls, some want owls and could care less about saving jobs, and lots of people want both. It is beyond the scope of this project to offer a resolution to this problem, but I would like to explain some of the reasons leading up to this conflict.
In 1984, a study showed that 97.6% of all spotted owl nest sites in Oregon were found in old-growth forests or forests containing a mixture of old-growth and mature timber. Some spotted owls were found in second-growth, i.e., younger forests that have been logged; however, these areas were found to contain characteristics typical of old-growth forests. No spotted owls were found in forests less than 36 years of age (Forsman et al 1984).
Does finding spotted owls in second-growth stands mean they can survive there. No. The real question is this: Can spotted owls reproduce successfully in these stands, to the degree that they would avoid extinction? Studies of spotted owls found in second-growth have shown the habitat to be marginal and unlikely to be suitable for long term spotted owl reproduction. The low density of spotted owls living in second-growth does not indicate they are likely to survive there (Forsman et al 1977). Another way to look at is: if they could live in second-growth, why are their numbers declining?
Between 1969 and 1978 spotted owl populations declined at an average rate of 0.8% per year, a seemingly small number but one that points towards extinction. Studies of this decline all point to the same cause: the elimination of their habitat due to logging practices (Forsman et al 1984). Old-growth forests once occupied over 20 million acres of the Pacific Northwest. Today there is approximated 2.4 million left and most of it is not protected (Committee on Agriculture 1989).
Another problem is that spotted owls require a large amount of old-growth to insure reproductive success, approximately 2000 acres. So, they not only need a diminishing resource, they need lots of it. Why old-growth forests and why so much it? Essentially, the spotted owl coevolved with old-growth and is physiologically and behaviorally adapted to it. Another question might be: what do old-growth forests have that second-growth forests normally don't? Old-growth is characterized by a dense, multi-layered canopy that provides shelter from heat and predators. Northern goshawks and great horned owls, which prey on spotted owls, have a difficult time flying and hunting within the multitude of limbs that create the dense forest canopy of old-growth. Spotted owls, being comparatively timid and unaggressive, find this kind of lush and impenetrable cover to their advantage. Old-growth also provides appropriate nesting sites and suitable habitat required by the spotted owl's major prey species: flying squirrels, voles, and wood rats (Gutierrez 1985).
But this doesn't explain why they need so much old-growth. Unfortunately, there is no precise answer to that one. It is simply a maximum number derived from studies of what they use. Since the spotted owl population is declining, it is thought that providing anything other than a maximum number would likely bring about extinction of the species (Forsmen and Meslow 1985). To make an human analogy, you can raise more children successfully in a 2000 square foot house than in a 100 square foot room.
But there is one thing I would like to make very clear. The controversy over "jobs vs. owls" is a battle between two sets of people, not between owls and people.