Depending on what materials nest boxes are made from, they will require more or less maintenance over their lifetime. Common annual tasks include ensuring all installed nest boxes are still attached to their trees, repairing any damaged nest boxes, replacing really gross bedding, and ejecting unwelcome occupants such as feral bees. Some species are tidier than others, you will find.
I paint (undercoat + 2 coats of exterior paint) our nest boxes – purchased or made myself, to improve their durability in outdoor conditions, and use all for-outdoors or stainless steel components for the nest boxes that I’ve made.
To improve the durability of your nest boxes, if making them yourself, be sure to use non-rusting components such as stainless steel hinges. The type of materials, such as hardwood offcuts and hardwood plywood, or cheap thin plywood, that the nest box is made from will also affect durability in the outdoor environment, and ability of vigorous chompers such as Galahs to damage the nest box. Thin plywood will degrade very quickly, followed by pine, hardwood plywood, hardwood timbers, with wood-like boards made from recycled plastic being the most durable.
Also your choice of attachment mechanism to the host tree will affect how likely it will be that the nest box will fall from the tree and be damaged in the process. Check out Hollow Log Home’s Habisure system in the book Nest Boxes For Wildlife. I’m a big fan of this system for being very sturdy, for not damaging the trees as they grow, and for being easily adaptable for all types of installation locations (forks, straight trunks, small & large trees). Less good are systems that involve drilling screws into trees, as this puts at risk the health and longevity of the tree. The wire used is 3.5mm and is plastic coated galvanised wire.
Occupation of nest boxes by pest species, and their removal is another task to include in your nest box maintenance plans. Feral honey bees are a commonly encountered unwanted nest box occupant, so too are ant nests, nesting Starlings and Indian Mynas. If you don’t have the know-how for removal, contact your local Local Land Services office, also Landcare, and Wildlife carer networks may be able to offer advice and assistance. We have Starings for the first time this year discover our nest boxes. I will remove any eggs and added-by-Starling nesting material shortly. I also removed an ant nest from one for-Rosella nest box last Summer, gently (on the ground, jiggling, tapping right way up, then upside down for the stragglers), so the occupants were able to rescue their eggs and carry them to a new temporary safe location while they figured out what to do next.
Some nest box occupants are tidier than others. Any unhatched, or abandoned eggs in a nest box used by Wood Ducks will remain and go rotten in time. Other species and also new Wood Duck families will often not use an unoccupied nest box with old duck eggs inside. I don’t blame them, rotten eggs are gross! Once any ducklings have hatched and departed, simply remove any whole eggs and dead ducklings, and any soiled (squashed egg) bedding. Ducks will remove duck egg shells before using a nest, but whole eggs are clearly beyond their abilities to eject.
Our Rosella and Kookaburra families make a right mess of their nest boxes also, with a deep layer of chick poo deposited and remaining after the chicks fledge. It’s quite revolting and surely couldn’t be good for any future sitting bird mum. I scrape these nest boxes out entirely after chicks have fledged, and add fresh bedding of wood shavings or chipped wood and bark.
There may be a queue for nest boxes during the nesting season, so cleaning out nest boxes once you know they have been vacated as a priority, will be much appreciated by the next occupants. I’ve had a new Wood Duck family begin to lay in a nest box just 3 days after the previous family hatched departed. I went to clean out the egg shells and any rotten eggs from a nest box vacated a week earlier, and instead discovered all egg shells were gone, and three clean new eggs were neatly laying in the bed of feathers!
Some other helpful resources:
Build your own nest box: a guide for Western Sydney (Greater Sydney Local Land Services): https://www.wires.org.au/wildlife-info/wildlife-factsheets/Wildlife-Nest-Boxes-LLS.pdf
Nest Boxes for the Gippsland Region (East Gippsland & Maffra and District Landcare Networks): https://egln.org.au/wp-content/uploads/2013/07/Nest-box-booklet.pdf
Nest boxes for Natives (Birds Australia): http://birdlife.org.au/images/uploads/education_sheets/INFO-Nestboxes-nativebirds.pdf
Yellow Box Woodland Nest Box Project (Connecting Country): https://s3-ap-southeast-2.amazonaws.com/connectingcountry/press/wp-content/uploads/2018/01/03130248/NestboxFieldGuide_FINAL.pdf
Nest Box and Hollow Habitat Assessment Teacher Information Pack (Government of South Australia, NRM Education): http://www.naturalresources.sa.gov.au/files/faa91938-4acf-4877-a4a3-a27a00dc3a49/amlr-me-schools-terrestrial-birds-nest-boxes-hollows-habitat-ass-gen.pdf
Wildlife Notes, Nest Boxes For Wildlife (Land For Wildlife, WA): https://www.dpaw.wa.gov.au/images/documents/conservation-management/off-road-conservation/LFW/Nest_Boxes_for_Wildlife.pdf
Bush Futures Nest Boxes For Wildlife (Tweed-Byron Bush Futures Project): https://www.tweed.nsw.gov.au/Documents/Environment/Bush%20Futures/TSC01135_Nest_Box_Manual.pdf