He is now 7 months and is starting to settle down and grow up all at the same time

We did have great recall, he would come back without any problem now however we are having a problem. He will come in the house or in from the garden when called. But when we go to the park he just won't come back.
He doesn't run away, he doesn't bother any other dog/person all he want's to do is chase a stick!! (or a bird

) Where is the problem I hear you ask? Well once I have thrown said stick he run's away with it and just eats it, you can't get anywhere near him while he has his stick as he just runs, lies down and starts eating. When I call him I have to have another stick in my hand, when he get's to me he won't even take a treat, only wants the stick.
He is so focused on this stick that he turns into a dog on a trampoline, he's only a pup but can still get his feet up to my chest. This means when we go home I have paw prints and slabber all over me!
Once I get him back with another stick and he's back on the lead he's so wound up walking is a nightmare, he's still bouncing about!!

Any suggestions or help would be so appreciated