I pulled all the data for Eugene from 1944 to 1999 and made
a graph of that data. What I see is an irruptive pattern
that has some correlation to Snowy Owl irruptions (though
someone with a statistical background might well prove me
wrong).

http://home.pacifier.com/~mpatters/cbc/seow.html

As to breeding numbers of Short-eared Owl, one would have to
find a reliable database likely to include SEOW (BBS data does
not really do this) to show any kind of trend. However,
"wild" edge habitat has been systematically discouraged throughout
the Willamette Valley along with intensive management of
agricultural land to maintain the monoculture (mostly through
chemical applications). Any decrease in plant biodiversity
invariably leads to a decrease in animal biodiversity.

--
Mike Patterson Alas, to wear the mantle of Galileo,
Astoria, OR it is not enough to be persecuted
celata at pacifier.com by an unkind establishment,
you must also be right.
---Robert Park
http://www.pacifier.com/~mpatters/bird/bird.html