The national trust birch log nest box is, as the name suggests, made from a natural birch log which makes it perfect for those who prefer a more natural look. The 32mm hole size is most suitable for a variety of tits and smaller birds.  there is a shortage of natural nesting sites, which is thought to be one of the major factors behind the decline of some of our once most common birds. By putting up nest boxes, such as this, which replicates a birdaposs natural nesting preferences, you can encourage them to breed near your home. Different species prefer different nest boxes and our range has been designed by our team of ornithologists to optimum dimensions for the species concerned. Look out for regular visitors to your garden and choose a box which best suits their needs. You can check this using our hole size guide. Https www.birdfood.co.uk about our nest boxes as this is a natural product the dimensions stated are approximate.