Pets motion alerts

HiI have two spotlight wired cameras (2nd Gen). I am receiving motion alerts from small things like birds and cats. The cats are setting off the motion detection in the early hours of the morning. I have the cameras fixed at the recommended height. The motion zones are set correctly and the motion sensitivity is very low. They never used to pick up small objects. What can I do to stop these false alarms and only pick up humans? It’s not very nice being alerted at 2am or 3am by a cat wondering around in the garden.