You may not think so but nesting sites are carefully chosen and branches close to the box which may provide access for predators is a minus. As above, if the box is inspected and the sun is on it, it will be rejected because it is too hot inside.
Many nestboxes sold are unsuitable for birds. A good nestbox should not have a perch under the hole and should be made of rough sawn wood - it is hard for them to start building a nest on a smooth bottom as the grass etc. will slip and slide all over the place except where the bird wants it to stick.
The best nestbox we've had is the old clay flowerpot with a 1" hole in the bottom, hung up top against the wall. It is amazing how small a hole a bird can get into, and they'll feel safer as less predators can enter.
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are subject to;
Access for predators to the nest(box) - branches close to the box is a no no.