When we are asked to design ecological mitigation schemes for developments we often suggest the incorporation of bird and bat boxes into the design. If we know birds and bats use the site, it can be a low cost solution to replace roost and nest sites that may be lost through development or even to enhance the site for wildlife.
We are currently in the middle of National Nest Box Week (14-21 February), an annual event that aims to encourage installation of nest boxes to promote conservation of our breeding birds and wildlife. Here is our and our simple ‘why, what, where and how’ guide to nestboxes:
Help with the housing shortage!
There are a lot of pressures on our native wildlife at present. New build houses are often impregnable to wildlife, lacking any gaps and crevices where animals may nest/roost which means that opportunities are reducing for many species. To look at this from a human perspective it is the avian equivalent to the housing shortage in Bristol, anyone who has tried to get on the housing ladder in the past couple of years will testify that demand is far exceeding supply. By doing something as simple as putting up a box on your house or in your garden, you can provide invaluable support to our urban wildlife that is in desperate need of somewhere to live too.
There are a great many designs and different types of boxes available, serving different purposes depending on the animals that use them. Bat boxes for example can be integrated into walls with an entrance allowing bats to access a small cavity, thereby avoiding having an external box on show. There are also boxes that can be attached to trees or walls of buildings. Boxes may be large, designed to host a hibernating colony of bats, or small, designed to support a few individual crevice dwelling bats. Bird boxes are likewise diverse in their appearance, specialised to different species requirements. Zero maintenance boxes are also available.
As mitigation/enhancement for development proposals, we usually specify boxes that are made from woodcrete, a mixture of cement and sawdust which makes very durable boxes that will last for years. However, if you are interested in putting up nest boxes on your home or garden, there are lots of wooden alternatives which may be less expensive.
Where to site your boxes
When siting a bat box it is best to place it as high as possible in a sheltered, sunny position, facing away from prevailing winds. On a building the box should be placed as close to the eaves as possible. Most species of bat use linear features in the landscape to navigate, so putting a box near a tree line or hedgerow may help bats to find the box. Try to avoid putting a bat box in a well-lit area, bats are often very light adverse so this will discourage them from using a roost site.
Siting of bird nest boxes depends on the type of box and what species you are trying to attract. However, good advice is to face the box north-east, as this will avoid strong sunlight and wind disturbing the box. You should also consider access for predators (siting a box in a hard to reach location for a cat is a very good idea) and ensure that there is a clear flight path to the box.
Don’t be tempted to peek …
Remember it is against the law to disturb a nesting bird so if you think a bird may be nesting in your box don’t be tempted to open it and have a look, as this may result in the bird abandoning the eggs or chicks and the failure of the clutch. If you have seen a bird carrying food back to the box it is safe to presume the eggs have hatched, it is especially critical not to disturb the box when the chicks are close to fledging as it may cause them to leave the box before they are ready.