Menu Close

Bats and Birds in Trees

bats and birds

Birds and bats are the two animals most likely to be an issue when carrying out tree work. For nesting birds, it’s often obvious when they are there and the approach is straightforward. For roosting bats, it’s not nearly so clear cut.

Both birds and bats are protected by current wildlife legislation. For birds, causing harm to them, or disturbing their nests, is an offence. For bats, harming individuals and disturbing their roosts, even if unintentionally, could lead to prosecution. Ignorance is no defence, and you need to be able to demonstrate you have done what is reasonable to avoid an offence.

For birds, if you spot an active nest (and you should always check before starting work), waiting a few days or weeks until it is empty is normally sufficient – easy to see and easy to deal with.

Knowing if bats are using trees is harder – they can be hidden in small spaces and only come out outside of normal working hours.

So what can you do to check? Firstly; bats often make use of the very same features in trees that may have prompted the work – cracks, hollows, holes, tight forks and crossing branches. So, if you have to work close to these, bats should already be on your mind. If you have these features, you need to assess if they could be used by bats. There may be three stages to this:

1. From the ground you can visually check to see if holes, cracks or other features you can reach are deep enough to be used – if you can’t see to the full depth, you can’t tell if bats are in there. For holes further up the tree, using a torch may help from the ground, if the extra light allows you to see the full depth, but beware of what you can’t see.

2. If you can’t rule out features at that stage, this is where you may require a licensed bat surveyor. They are able to carry out a more invasive inspection, possibly using a mobile platform or climbing the tree for features too high to reach otherwise. This will involve using a high-powered torch or endoscope. Unless you have a licence, you cannot use these yourself to look for bats – potentially you would be committing an offence!

3. Even a licensed surveyor may not be able to tell you one way or another at that stage, if for example they cannot see in sufficiently far, or if they find signs that bats may be present, but aren’t at the time they look. Then the licensed surveyor will need to carry out an emergence or re-entry survey, watching the tree from just before sunset until it is dark to see if any bats come out, or at the end of the night to see if any return to it.

If bats are found, then you may require a licence to carry out the work – the surveyor will be able to tell you what needs to happen next. If the surveyor confirms no bats are present, you can go ahead, though still taking a precautionary approach still, in case bats are present but not active that night. Again, the surveyor can tell you what you need to do. This approach demonstrates you have done all that is reasonable to prevent harm, possibly a crucial factor in the event a bat is still inadvertently harmed during the work.

Find out more

At agb Environmental we have a team of ecologists who are ready to survey for bats and nesting birds. The team also includes a fully qualified tree climber, licensed to survey for bats. To discuss to see how the ecology team can assist with your next project, call Richard Parmee (Head of Natural Environment) on 01638 663226 or email

Ecology, News, Surveys