Russell,
Not that I have any expertise whatsoever on the subject of wildlife
photography, but I'd say also that primes are definitely the way to
go. And you will always want more "reach" than you have. Seems like
in order to get really close for those frame filling shots that
shooting from a blind produces the best results. Especially with the
more skittish species.
At least with the Pentax equipment that doesn't have image
stabilization built in.
I have been very satisfied with a relatively new enablement in the
Tokina AT-X 400mm f5.6. This is the same lens that Bruce and a few
others here also have. It is light and small for a 400mm prime; very
hand-holdable on bright days. I haven't taken a lot of time yet to
see how it works with a 1.4X teleconverter for extra reach. Here is
a recent shot grabbed in my front yard:
http://i.pbase.com/o4/87/63987/1/58830040.YardBird.jpg
Too bad they discontinued this lens. I too would be tempted to get
another if it came up available. I don't think however that the lens
mentioned by William as going for $40.00 on eBay is the same. There
is another version (manual) by Tokina; the SL I beleive, but it is
not the same or even close in quality to the AT-X SD version.
Good luck with your search,
JayT
