Our garden backs onto a strip of municipal woodland. We have a metal
support for hanging cage-type bird feeders, and attract a good number
and variety of small birds.

We also attract many pigeons, which can't properly cope with the cage
around the feeders, but also three or four grey squirrels which pay a
visit several times a day.

They don't tend to go for the bird seed feeder, but go instead for the
peanut feeder, having learnt to clamber inside the cage part and feed
upside-down on the peanuts in an inner, small-meshed cage. A pack of
peanuts costs me 99p, and one, thanks almost entirely to the squirrels,
lasts a day at the most.

Spraying the metal pole with WD-40 stops the squirrels as they slither
around and can't climb it, but this lasts only a couple of days, and
costs more than the peanuts if I kept refreshing the WD-40. I suspect
that someting other than WD-40, such as soap or an oil, would no last
much longer before the little critters are able to shin up the pole
again. (The pole etc is not near a tree of fence, but the squirrels
cross the lawn to it and race up it - amusing the first few times, but
now infuriating!

Can anyone suggest a low-cost deterrent which will not harm the
squirrels but would allow the other birds (Most of which seem to prefer
peanuts to wild bird seed) to feed on the peanuts?

Thanks in advance for any advice,

Bill.