A bug crept into the last update of Bird Guide Britain and messed up the lists of seen birds and starred birds. We have made a fix which will return the lists to their previous state, but unfortunately if you have already gone through the app and corrected the list yourself, you will have to do it all again when the update comes out. We are really very sorry about this :(. We looked into all the possible ways of correcting the fault, but the more complicated the fix, the longer it would take to implement and test, so we decided that the best course of action is to release a quick fix as soon as possible to minimise the number of people affected.
We've asked Apple to prioritise the update (which they do in cases like this) so it should be out in a few days.