I have a nest box with a camera in it and over the past couple of months a pair of great tits gradually built a nest in it. After a couple of weeks the male began sleeping in it but recently the female has also decided to sleep in it but the male refuses to relinquish it and now every night the pair of them have a bit of an argument as they each try to have the comfy spot and they give each other a good pecking before eventually the female wins and the male gives up and sleeps in the corner. As time has gone on they squabble less and less and have accepted each others company. However yesterday the female laid her first egg and tonight both the birds are in the box yet again with the female sat on the egg and the male in the corner. My understanding is that the eggs aren't supposed to be incubated until after they have all been laid so that they all hatch at the same time, however the female is clearly sat on top of it, and even if she wasn't I reckon the male would be because its in the comfy part. I also thought that the male isn't supported to sleep in the box. Are they doomed to make a mess of things or is all this pretty normal?
Here is a nice picture of them sleeping by the way
I came back to give an update. The male did not return to the nest all day until almost 8pm and then he tried to sleep in the next again, but as soon as he saw there was an egg there his behaviour has changed completely and he no longer sleeps in the nest! The female laid a total of 4 eggs but unfortunately she ate 2 of them (I think she accidentally broke them while scratching around in the nest). For the past week she has been incubating just the 2 eggs and the male only comes in the nest to feed her. Its a shame there are not more but 2 is better than none I guess :)