Hi , we noticed a nest in one of our bushes and it had two small blue eggs and two cream and brown speckled eggs. We saw the mother sitting in there and she appears to be a sparrow. Later on we looked and all the eggs were gone. The next day we looked again and they were back in there again except for one of the blue eggs. Total two cream/brown and one blue egg now. The mother was back too. Is this unusual? Why would she remove them and then put them back and why are there two different color eggs? Just curious!