Wood pigeons nesting

I have wood pigeons nesting in my Magnolia tree above the patio, the tree needs cutting asap but obviously I don’t want to harm the birds. The mother has been on the nest at least 24 days, I’m sure she leaves to eat at some point but she’s always there when I look and she’s directly above my table and chairs so that’s often. 
      I’m wondering how long this is likely to go on as it’s quite stressful waiting for the chick if there is one when I have two very interested cats!