National Nestbox Week

This week is National Nestbox Week, an initiative that runs from Valentine’s Day each year to raise awareness of the need to

National Nestbox Week
Dr Simone Webber
May 23, 2022

This week is National Nestbox Week, an initiative that runs from Valentine’s Day each year to raise awareness of the need to provide extra nesting space for birds. It is the perfect time to install a nestbox in your garden as the birds are just starting to form territories for breeding. Many of our common species struggle to find natural nest sites and providing a nestbox offers them a safe site to raise their young, as well as providing you with a fascinating glimpse into their breeding biology. Choosing and installing a nestbox can seem a little daunting but with our nestbox guide, you should be able to provide a valuable nest site for birds.

Why do birds need nestboxes?

Modern houses and gardens tend to be very tidy, without crevices for cavity nesting birds to nest in, and lacking undergrowth for open nesting birds. Cavity nesters such as blue and great tits need a hole in a tree which is secure from predators to nest and raise their young. We tend not to leave dead wood standing in woodlands or gardens, and so natural nesting sites have become very rare. A nestbox is the perfect alternative and species such as blue tits, great tits, coal tits, house sparrows and nuthatches will all readily use nestboxes. Nestboxes are also important as roosting sites during the winter, providing safe shelter for single birds or colonies of wrens.

Open nesting birds such as robins, wrens and blackbirds need secure nesting sites in corners overgrown with ivy or bramble, so it is good to leave an area of your garden to go a bit wild. You can buy open nestboxes, but dense cover is the most important feature that will encourage them to nest and protect them from predators.

If you have swifts nesting in the area, then installing swift boxes can greatly help their breeding success, as many of their nest sites on buildings have disappeared due to modern building methods. For swallows and house martins it is more useful to have a ready supply of mud, so it is a good idea to keep an area of your garden a bit damp so they can construct their own nests.

The breeding biology of cavity nesting species

Adding nestboxes to your garden provides gives you a fascinating insight into the breeding cycle of your avian visitors. The cycle starts in March for common species that use nestboxes, with establishing territories and finding a mate, then selecting a nest site and building a nest. Blue and great tits are reliant on moss to build the bulk of their nest structure and then they line the nest cup with grass, feathers (blue tits) or mammal hair (great tits). House sparrows build a nest from dry grass or straw and then line it with feathers or hair. Great tits frequently pluck hairs from dead animal carcasses so their nests can be somewhat fragrant, but they will also use pet hair that is left out in the garden.

Great tit (Parus major) eggs. Photo credit: S. Webber

The first eggs usually appear in April and then the female will start incubating the eggs towards the end of the month. The male will deliver food to the female while she is incubating the eggs and you may see him call her out of the box first thing in the morning with some breakfast. The first chicks usually appear in May, which is when you will see both parents delivering caterpillars, spiders, and other insects to the box at an astonishing rate. The chicks will stay in the nestbox until about 19 to 20 days after hatching, becoming increasingly noisy and peering out of the box as they get ready to leave. Chicks of open nesting species leave the nest much earlier, about 14 days after hatching and then hide in the undergrowth near the nest. Once the chicks fledge, the parents continue to feed them for another two weeks or so, which is thought to be a critical point in determining offspring survival as they are taught about foraging and predators.

How to choose a nestbox?

There is a vast array of nestboxes available to buy and the choice can be bewildering. The first thing to consider is which species are visiting your garden and are likely to use it. Blue and great tits are ubiquitous and most standard nestboxes will attract them. A simple wooden nestbox with a hinged lid allows you to clear out the nestbox at the end of the breeding season (August) and is a great choice to see if there is any interest from birds. Alternatively you could choose a nestbox made of a concrete and sawdust mix, such as the Schwegler Woodcrete boxes or the Vivara Pro WoodStone boxes. These are much more durable than wood and can last for 10 years or more.

The best size of entrance hole is 32mm if you are starting with a new nestbox, as this will attract a broad range of species. You can choose a 26mm hole if you want to restrict the box to use by blue tits or smaller species. If you are lucky enough to have starlings then a box with a 45mm hole will suit them. House sparrows nest in colonies so prefer a house sparrow terrace, which is usually a set of three nestboxes with 32mm entrance holes.

Where to site a nestbox?

Nestboxes are best sited at least 2m off the ground and away from prevailing winds. This means that for most of the UK it is preferable not to face nestboxes in a south-westerly direction. Attach your box to your house, fence or a tree and ensure that there is some tree or hedge cover relatively close so that the birds have a short flight into the box. For house sparrows you need to site the box on your house as close to the eaves as you can. Similarly for swifts or house martins, nestboxes should be up under the eaves. If you are providing a nestbox for open nesting species, then it needs to be sited amongst ivy or bramble.

The magic of nestbox cameras

Investing in a nestbox camera adds an extra dimension to the wildlife experience in your garden as it provides a detailed insight into the birds breeding in your nestbox. Choosing a nestbox camera is a question of location, as they can run on their own wireless network, be directly cabled to a TV or PC, or be connected in to your WiFi network. All the cameras will need to be powered so they will either need a mains power socket nearby or a solar panel. Many of the apps that come with WiFi adapted cameras are free and you can watch or record amazingly clear footage on to your tablet or phone. If you are intending to install a nestbox camera then it is best to do this as early as possible, before the birds start building a nest in March.

When creating our new forest sites, we will be installing nestboxes to provide nesting space for the birds in the area. As our woodlands age, we will be leaving dead wood where we can, which will provide natural cavities for many species to nest.

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