cherry tree advice please

when should i prune my cherry tree  please ,its been on my plot for three years but im guessing its about 5/6 years old,as it was already there when i took it on,

sadly thios year i only got one cherry off it as the birds had a feast on it,they year before i had about 40 cherries,
I am findinf thats its too big now to net over and dont want the birds getting trapped under any netting i place on top.
it prouduces lovely sweet cherries,any advice on pruneing it and tips on netting it are most welcome please

ey up jen
if you dont want to net your tree then dont
get yourself some rubber/plastic snakes connect the tail to the tree and with some fine fishing line connect the head so that it swings in the wind. the birds wont come anywhere near your fruit trees.[ in italy they use real snakes in demijons]

Jen, it wont hurt to take the offending branches out. Just don`t overdo it.