Ecology evidence for a redundant barn surveyed in winter

A redundant stone barn inspected in January can tell you a great deal and prove almost nothing. A barn ecology survey winter visit establishes the structural features, the access points, the presence of historic droppings and the suitability of the building for roosting, and it cannot establish whether bats are using it, because the emergence and re-entry surveys that answer that question only work between May and September. Councils know this. The practical issue is what they do with an application submitted on a winter assessment alone.

What a winter visit can and cannot establish

A preliminary roost assessment can be carried out at any time of year. The surveyor records the building's construction, the condition of the roof covering, soffits, ridge tiles, lifted slates, mortar joints and timber frame, the gaps that give access, the internal flight space and the lighting and connectivity of the surrounding habitat. All of that is season-independent.

Field signs are where winter helps. Droppings accumulate and persist, so a scatter below a ridge beam in February is good evidence that bats have used the building. Urine staining, scratch marks, feeding remains such as moth wings on a ledge, and grease marks around an access point all survive the winter.

What cannot be established is absence. No droppings in an unheated stone barn with multiple access points does not mean no roost, because droppings get swept, eaten by invertebrates, or deposited somewhere the surveyor cannot see. Nor can the roost type be characterised, which matters because a maternity roost and a transitional day roost carry completely different mitigation and licensing consequences.

Hibernation surveys exist, but they are a poor substitute. Bats hibernating in a crevice are not visible, detectability is low, and a negative hibernation check adds little.

Writing the preliminary roost assessment so it is usable

A Preliminary Ecological Appraisal or a dedicated roost assessment carried out in winter is still a worthwhile document, provided it does three things.

It assigns a roost suitability category, using the Bat Conservation Trust good practice guidelines, with reasons tied to the features observed. Negligible, low, moderate or high, and the category drives the number of further survey visits required.

It states the survey effort the guidelines recommend for that category, with the months in which those visits can be carried out. A moderate suitability building needs more visits than a low suitability one, and the guidelines set out the expected pattern.

It separates fact from inference. The features are observed. The suitability category is a judgement. The conclusion about likely presence is an inference, and it should be labelled as one.

A report that does all three gives the case officer something to work with. A report that concludes "no evidence of bats was found and no further survey is required" after a February visit to a barn with lifted slates does the opposite, and it is the most common reason ecology comes back as a validation query.

Barn owl evidence, which winter actually suits

Barn owls are a Schedule 1 species under the Wildlife and Countryside Act 1981, which makes disturbance at or near an active nest an offence, with an additional offence for disturbing dependent young.

Unlike bats, barn owls can be surveyed by field signs through the winter, and winter is often a good time to do it. The signs are durable and distinctive: pellets, which accumulate in quantity below a regular roosting or nesting site, whitewash splashes, moulted feathers, and a nest scrape of broken-down pellet debris in a loft, on a beam, or in a hay bale void.

Barn owls use sites through the year rather than only in the breeding season, so an occupied site is usually detectable in winter. Breeding is the part that needs a growing-season visit, because the presence of eggs or young is seasonal and the breeding period can run from early spring into late summer, sometimes with a second brood.

Where signs are found, the usual outcome is a barn owl mitigation scheme: retention of access, a nest box in the converted building or on an adjacent structure, timing restrictions on works, and a condition securing all of it. That is deliverable and rarely blocks a scheme. What blocks schemes is finding the owls after the roof has come off.

Reporting limitations without undermining the report

Honest limitation reporting makes an application stronger, not weaker. The section should state the date and time of the survey, the weather, the areas that could not be accessed and why, the seasonal constraint, the survey effort the guidelines recommend, and the residual risk in plain terms.

Then say what happens next, with dates. Not "further survey may be required" but "two emergence and re-entry surveys are required, to be carried out between May and August, on dates at least two weeks apart, following the guidelines for a moderate suitability building". The further survey section of an ecological appraisal sets out how that recommendation should read.

The limitation that gets hidden most often is incomplete internal access. A barn full of straw bales or with a collapsed floor cannot be fully inspected, and saying so is better than implying a complete survey.

Conditions that defer survey work, and when they are wrong

Government guidance on protected species is clear in principle: the presence of a protected species is a material consideration, and surveys should normally be completed before the application is determined, because the survey result may affect whether permission should be granted at all and what conditions are needed.

A condition requiring surveys after permission is therefore inappropriate where the survey could change the decision. It is acceptable where the survey only informs the detail of mitigation that is already known to be achievable.

In practice the line falls roughly here. Deferring survey work is defensible where the building is of low suitability, the works are limited, and any likely roost could be accommodated by standard mitigation. It is not defensible where the building is of moderate or high suitability and a maternity roost would require a European protected species licence that might not be granted on the scheme as designed.

A Protected Species Survey and any licence application require a suitably licensed ecologist under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017. That is a legal requirement, not a preference, and no draft document substitutes for it.

Determining without a survey, and the Class Q wrinkle

Where an authority grants permission without the survey, two risks follow. The applicant may commit an offence once works start, since the licensing regime operates independently of planning permission. And the decision may be open to challenge on the ground that the authority failed to have regard to its duties under the Habitats Regulations.

Class Q of Part 3, the agricultural building to dwellinghouse route, creates a particular trap. The prior approval matters listed for Class Q do not include ecology, so the authority cannot refuse prior approval on protected species grounds. That does not help the applicant. The licensing regime still applies, and the authority still has duties under the Habitats Regulations when exercising its functions. Converting a barn under Class Q without a bat survey leaves the developer exposed to the offence, not protected by the absence of a planning ground.

Worth noting alongside that: development permitted by the General Permitted Development Order sits outside the biodiversity gain condition, so a Class Q conversion does not carry the 10 per cent requirement while a full application for the same building does. That asymmetry pushes some schemes towards Class Q for reasons that have nothing to do with ecology.

Planning the survey programme backwards

Work from the season, not from the design programme.

1. Fix the emergence survey window. May to September, with May to August the stronger period for maternity roosts.
2. Count back the number of visits the suitability category requires, allowing at least two weeks between visits and allowing for weather losses.
3. Allow four to six weeks after the final visit for reporting.
4. Allow for a licence application if a roost is confirmed, which takes further weeks and needs the mitigation designed first.
5. Then set the submission date, and the start on site date, from that.

A barn assessed in December with moderate suitability realistically cannot have a complete bat survey package before July. Telling the client that in December is the whole value of the winter visit. Scoping the full set of supporting documents at the same time means the drainage, structural and heritage work runs in parallel rather than afterwards.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Bat and barn owl survey work, and any mitigation licence, legally require a suitably licensed ecologist, so a draft is only a starting point for that professional. This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.