The loss of hedgerow trees, changes to woodland management and increasing urbanisation have all contributed to a decline in the availability of natural sites for cavity-nesting species like Blue Tit and Starling. Species that nest alongside people, such as House Sparrow and Swift, have lost out to changing building regulations, which have reduced the opportunities for birds to nest under roof tiles or in holes in barge boards. Well-designed nest boxes can replace these lost opportunities, increasing the numbers of nesting birds and boosting their populations, while providing the opportunity to collect valuable data. This guide provides the essential information that will enable you to find or build the right nest box for your garden, so you can do your bit to help our breeding birds.