it looks a bit like droppings from a small grub/caterpillar. have a closer look and see if you can spot any critters.

if its not moving it could be fly poo if it is flat black dots try to rub it off with a damp cloth.

Seaburngirl, have looked butt cannot see any grubs......Vicky they are flat, and will rub off, but cannot see any flies?

The leaves dont look troubled by them do they/
I think unless it is getting worse and the leaves are distorted or eaten that it s just insect poo even though you cant see the flies sometimes they are only there for a short time
of course it could be something else just give it a quick spray with water and wipe off marks then you can see if they came back