Build your own bird nestbox by 1 April 24, 2013 Use a 42mm hole diameter for starlings or a 32mm hole for sparrows. Ensure that sufficient drainage holes are drilled in the base of the nesting box. Use a eco-friendly preservative finish on the exterior only. To purchase a hand-crafted ready made bird nesting box <ClickHere> For information on cleaning and maintaining your nest-box. Check out our range of quality hand-crafted bird, bee, butterfly and hedgehog nesting boxes, feeders and shelters. Share Share on Facebook Tweet Tweet on Twitter Pin it Pin on Pinterest