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 bird\'s 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 using our hole size guide. The National Trust BYO Nest Box Kit comes with everything you need to produce your very own nest box for generations of garden birds to come. Contains: Pre-cut wood sections, all screws, nails, washers and a hanger. Includes clear instructions. This 32mm hole nest box will be used by Great Tits, Pied Flycatchers, Tree Sparrows and House Sparrows.