I have a wooden shed and on the side of it near to the top, I have fitted a
nesting box for bluetits, which they are just staring to know is there.

This morning at 5am, the wife had to get up and whilst walking across the
landing looked out of the staircase window and saw the local ginger cat
first sat on top of the shed then it started sniffing and pawing the bird
box. Now that it knows the bird box is there it will no doubt be coming on a
regular basis.

Unfortunately, I can not put the bird box anywhere else so what can I do.

I had thought of putting nails on top of the bird box to deter the cat, but
I do not want to harm the birds. I thought of putting a strip of nails on
top of the shed above the bird box, but there again it may be harmful to the
birds. Then I suggested to the wife that stay on guard duty every night, but
all I got was a wallop across the lughole.

Any suggestions please?

James