By the time you get done with all this, just get a vcr and a camera
and an 8 hour tape and leave it running at night.  Put a motion detector
light where it'll do some good (you might want to aim for getting thier
car on tape unless you think they're doing this all on foot..) and maybe
even use a pic to make the light turn on after a few minutes instead of
immediately.
  And don't just let the police do the dirty work.  Make copies and give
one to their parents if it's kids, or maybe their employer.  If they go
to church make sure and go there and let everyone know how you caught
them stealing from you..  Also make sure it gets good coverage in the
local gossip rag/town newspaper.  In a small town humiliation and
publicity make excellent deterrents.
  Also check your local laws on theft.  If the limits to move the crime
up a class are reasonable (say $200ish) and they are taking enough bulbs
at once, it may be worth the one time investment to get expensive
bulbs.  I'm sure you can find some hi-rel long life bulbs in the $20
range.  Would be worth it if made it into a felony theft..  Or leave
some old piece of electronics handy to bring the value up, since most
thieves are opportunists.  There could also be some endangerment charge
applicable since the lights are critical to being able to land safely..