In my inventory I have 4 Pirate maps. Three of them are in brackets. One of them is in my shop for sale. But when I go to capture a horse the maps do not come up as items on the drop down.

How can I use these maps?

I think you have to remove them from your shop first before you can use them

No, surely this is an error. Only one is in the shop. The other 3,should be useable.

I used all of mine, bracketed and otherwise for questing day before yesterday.

Are you checking in the very bottom field in the capture screen?

Just have to ask the obvious to exclude that.

Only one map is in my shop. When I click on the Use Items drop down on the capture page there are no maps shown. I am just trying to get rid of them,