The Wrong Tenants?

I made this Semi-detached residence from an old box. The holes are "House Sparrow" sized and the box is sited on the garage wall. House Sparrows are supposed to like neighbours and I was hoping that they'd use the box instead of the eaves of the house. They seem to prefer the house and the Great Tit pair is in residence rather than using either of the "Great Tit Boxes" I've put up.

When they arrive at the box, they don't hang around, it's straight in. I guess this is sensible and doesn't help any predators about. Above you can see the Caterpillar it is carrying. They are quite shy, and refuse to go to the nest if they see a human near. I've hidden myself in the back door porch, about double the distance I'd like to be to get better pictures.

It normally hardly stops and if I put the camera on multiple shots I get one of the bird entering flanked by two of the nest box and no bird!

On its way out it is just as fast. They're quite good house keepers, and this one is taking out a faecal sack, a neat package of waste that it was presented with by one of the young. Unlike many seabirds, like cormorants or penguins, most small birds keep their nests clean.

Once out, it's up and away to find more food for the brood. Most of the food is caterpillars. but they also seem to pop onto to the sun-flower heart feeder every now and again.

This was unusual, when she got there the male was already inside feeding the kids, and instead of joining him she stayed outside until he left, after just a few seconds. She would have been vulnerable during this time had there been a predator about, but it gave me a second to take a photo.