Party wall stepped terraced house

[Da1]

Hi guys looking for some advice. I live in the white house the wall going from my roof where the me and the next house share the wall and chimney stack has some holes in it and birds are nesting in the chimney stack which is no bother to me but my neighbour is complaining they are dropping things on their roof and blocking their gutters… the wall is between out properties and the boundary is in the middle is this wall at the top mine? the side with damage is over his boundary line