Do Blackbirds ever leave a gap between laying eggs and incubation?

I found a Blackbird's nest in my garden on April 18. That afternoon I saw a bird in there. After that I didn't see any bird go in the nest. I'm not sure if there were 3 or 4 eggs at the time. I took a picture but bush leaves were covering the view. Today there are 4 eggs in the nest. There are also some small leaves in the nest, like it's been abandoned. Is this how it usually goes? I haven't touched it, just kept a look at it from a distance. That's almost a week with no movement and I'm finding it odd. Cheers