This nest box has been attacked.
I do not know what type of wood the nest box is made of but it is thinner than the usual nest boxes that I buy. This photograph was taken last year when it was fine and sunny.

Predator has been trying to get at the eggs or chicks
Woodpeckers drill an entrance with their chisel beaks
I think that is what has happened in the photo above.
It’s a case of bird eating bird again.
Squirrels, weasels, cats, crows and great spotted woodpeckers are among the predators of birds.
Our garden birds are subject to attack from ground and air.
I do have other nest boxes that are stronger which have not been attacked.
There are ‘guards’ that can be put over a bird box entrance hole.

These plastic guards cost £5.99 and these seem a good idea as they stop predators attacking the actual bird box entrance. Take a look at how to purchase the BIRD GUARDIAN
Tough woodcrete nest boxes are very good as predators cannot make the entrance holE larger so they cannot get to the eggs or chicks inside – which is what has happened in our nest box in the photo
SCHWEGLER 3 HOLE NEST BOX

£23.99 plus delivery charges – it will last years and as well as giving protection to the birds inside it gives a good insulation which helps chicks in the nest during their vulnerable time in the nest.
To find out all about the Schwegler 3 Hole Nest Box CLICK HERE