Dog chasing bats/birds & trees??

We have a 7mth old border collie who has become very focused on our back yard running around looking up & jumping up at the trees. This is often when there are birds around, but she has also started to do this at night which we think is linked to their being bats in the trees. The problem is that she will run around from tree to tree constantly for up to an hour & won't come to us when we call her, even when we have treats. Normally she would come without any problems & gets excited to see us until this started 3wks ago.
   
Any advice on how to stop or change this behaviour would be greatly appreciated. We want her to want to spend time with us over chasing the trees.
   
Thank you.