Checking trees for bat roost features before felling

Bat roost features in trees are assessed before felling because destroying a roost is an offence whether or not bats are in it at the time. Protection under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017 attaches to the breeding site or resting place, so a woodpecker hole used by a single pipistrelle for three weeks a year is a roost. For anyone reviewing a felling proposal, the first question is what features the tree holds and whether anyone has looked properly.

Tree work is where this goes wrong most often, because the contractor is on site for a day, the tree looks unremarkable from the ground, and nobody commissioned an inspection.

Features that indicate roosting potential

Bats use tree features that stay dry, hold a stable temperature and offer a crevice or cavity. The list is short enough to memorise.

Woodpecker holes and the cavities behind them. Knot holes and the sockets left where a limb has torn out. Splits and shakes along stems and branches, especially where they have started to close over. Lifting, loose or peeling bark on dead or dying stems. Hollows in old pollards and veteran trees. Compression forks where two stems press together. Frost cracks. Dense ivy stems on a trunk, which create sheltered spaces behind them.

Dead and declining trees carry more features than healthy ones, which is why blanket removal of standing deadwood on a site is a problem rather than tidying. Veteran and ancient trees carry the most, and they are usually protected for other reasons too.

Ground level assessment and its limits

The first stage is a preliminary assessment from the ground, using close-focus binoculars and a high-powered torch, ideally when the tree is out of leaf.

It does two things well. It finds features, and it grades the tree for potential. It does one thing badly, which is confirming the absence of a roost, because most features cannot be seen into from below.

That limitation should be stated plainly in the report. An assessment that concludes no evidence of bats was recorded from ground level, without saying what could not be seen, is not a basis for felling.

Where the tree can be retained, the assessment can end there. Retention avoids the whole question, and on a development site that usually means adjusting a layout rather than abandoning it. Our note on clearing a site before applying covers why early clearance creates both legal and planning problems.

Climbing inspection and endoscope survey

Where a feature is present and the tree cannot be retained, the next stage is an aerial inspection. A climber accesses the feature and inspects it directly, usually with an endoscope and a torch.

The team needs two competencies. Arboricultural climbing competence to work at height safely, and ecological competence to identify droppings, staining, feeding remains and bats themselves. Where a bat may be disturbed or a roost entered, the ecologist requires a licence from Natural England.

Findings are recorded feature by feature, with photographs, the height and aspect of each feature, its dimensions, its condition and what was found inside. A feature that is blocked with debris or full of water is reported as such, because that tells you something.

Aerial inspection reduces uncertainty. It does not eliminate it, because bats move between roosts and a feature empty in March can be occupied in June. Where uncertainty remains and the feature has moderate or high potential, emergence surveys from the ground in the active season are the next step.

Seasonal constraints on survey and felling

Two things are pulling against each other. Features are easiest to see when the leaves are off, and bats are easiest to detect when they are active. Programme the inspection for the winter and leave time for surveys in the following summer if the inspection finds something.

Breeding birds add a second constraint. The nesting season, broadly March to August, restricts felling and heavy tree work regardless of the bat position, and a nest in use is protected in its own right.

Licensing where a roost is confirmed

If a roost is confirmed and the tree has to come down, a European protected species mitigation licence from Natural England is required before the work starts. The application needs a method statement, a justification against the licensing tests, and a mitigation and compensation proposal.

Compensation for tree roosts usually means bat boxes in retained trees nearby, sometimes several per roost lost, sited to reflect the aspect and height of the original feature. Where a veteran tree is involved, retaining the monolith as standing deadwood is often better than felling it entirely.

Licence determination takes time. Build it into the programme as weeks rather than days, and remember that a licence cannot be granted retrospectively after the tree has been felled.

A Protected Species Survey is a report type where a licensed ecologist is legally required, and an AI-assisted draft is a starting point for that ecologist rather than a substitute for the survey or the licence application.

Soft felling and its limitations

Sectional dismantling with sections lowered under control, laid out and left overnight before chipping, is a precautionary method for trees with low roost potential. It gives any bat present a chance to leave.

It is not a licence and it is not a survey. Using it on a tree with a confirmed or high potential feature does not make the work lawful, and an ecologist who signs off soft felling in that situation is exposed.

Where it is used, someone competent should be present during the work, with a plan for what happens if a bat is found. Work stops, the section is left undisturbed, and the ecologist takes over. That instruction needs to be given to the climbing team before the saw starts, not written in a report they never read.

Recording the assessment for the file

Keep a record that would satisfy someone asking the question two years later. The survey date and weather, the surveyor and their licence number, the equipment used, the features recorded with photographs, the grading of each tree, what was inspected aerially and what was not, and the recommendations.

A tree survey to BS 5837:2012 records tree condition and constraints for design purposes and does not answer the bat question, so the two surveys sit alongside each other rather than one replacing the other. The bat survey page covers the survey work in more detail, and our note on penalties for damaging a protected tree sets out the separate offence that applies where the tree itself is protected.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.