This is our first year trying to get a bluebird family. There had been tons of activity at the bird house and we were sure they had built a nest. Last Sunday the birds were around a lot and the mother bird was in the house a lot. Unfortunately, we have a neighborhood cat who was all over our yard that same day. Our yard is fenced in but he is great at getting over the fence. I had chased him out several times and the last time I went around the fence to try to really make him run away and low and behold, he had the father bird in his mouth. Luckily he dropped it and the bird flew away. The next day we opened the box to see if there were eggs and there were 4 perfect blue eggs! This week we have seen the parents around sporadically-the father more than the mother, but no one is spending time in the bird house. Should they be? Also, yesterday and today I’ve seen them going in with branches appearing to build more nest. Does this mean the first eggs weren’t viable and they are building over the first nest? Not sure what to do. Thanks in advance for any help.