Ecological Survey Calendar: When Each Survey Can Run

Month by month

Dark months are the best time, pale months are possible, blank months are out of season.

Swipe the table sideways to see every month.

Survey	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Notes
Preliminary ecological appraisal	Jan: Possible	Feb: Possible	Mar: Possible	Apr: Best	May: Best	Jun: Best	Jul: Best	Aug: Best	Sep: Best	Oct: Possible	Nov: Possible	Dec: Possible	Any time; plants easiest to identify in the growing season
Bat roost assessment (PRA)	Jan: Possible	Feb: Possible	Mar: Possible	Apr: Possible	May: Possible	Jun: Possible	Jul: Possible	Aug: Possible	Sep: Possible	Oct: Possible	Nov: Possible	Dec: Possible	Any time of year
Bat emergence surveys	Jan: Not possible	Feb: Not possible	Mar: Not possible	Apr: Not possible	May: Best	Jun: Best	Jul: Best	Aug: Best	Sep: Possible	Oct: Not possible	Nov: Not possible	Dec: Not possible	May to September; May to August for some visits
Great crested newt eDNA	Jan: Not possible	Feb: Not possible	Mar: Not possible	Apr: Best	May: Best	Jun: Best	Jul: Not possible	Aug: Not possible	Sep: Not possible	Oct: Not possible	Nov: Not possible	Dec: Not possible	15 April to 30 June only
Great crested newt population	Jan: Not possible	Feb: Not possible	Mar: Possible	Apr: Best	May: Best	Jun: Possible	Jul: Not possible	Aug: Not possible	Sep: Not possible	Oct: Not possible	Nov: Not possible	Dec: Not possible	Mid-March to mid-June; two visits mid-April to mid-May
Reptiles	Jan: Not possible	Feb: Not possible	Mar: Not possible	Apr: Best	May: Best	Jun: Possible	Jul: Possible	Aug: Possible	Sep: Best	Oct: Not possible	Nov: Not possible	Dec: Not possible	April to September; mid-summer heat is less reliable
Badgers	Jan: Best	Feb: Best	Mar: Best	Apr: Best	May: Possible	Jun: Possible	Jul: Possible	Aug: Possible	Sep: Possible	Oct: Possible	Nov: Possible	Dec: Best	Most of the year; easiest before vegetation grows
Breeding birds	Jan: Not possible	Feb: Not possible	Mar: Possible	Apr: Best	May: Best	Jun: Best	Jul: Possible	Aug: Possible	Sep: Not possible	Oct: Not possible	Nov: Not possible	Dec: Not possible	March to August
Biodiversity net gain baseline	Jan: Possible	Feb: Possible	Mar: Possible	Apr: Best	May: Best	Jun: Best	Jul: Best	Aug: Best	Sep: Best	Oct: Possible	Nov: Possible	Dec: Possible	Condition is scored best April to September

From the Bat Conservation Trust’s guidelines (4th edition), Natural England standing advice and Natural Resources Wales guidance. Exact timing depends on the weather and the ecologist’s judgement for your site.

How to plan around the seasons

Start with a survey that can be done any time. A preliminary ecological appraisal, or a bat roost assessment for a building, tells you within a few weeks whether any seasonal surveys are needed at all. Many sites need nothing more.

If the first survey recommends bat emergence surveys or a newt water sample, book them at once. Ecologists fill their May to August evenings from early spring, and the newt sampling window lasts only eleven weeks.

Line up the design with the timetable. If the planning decision has to wait for summer surveys, use the time to settle the drawings and any biodiversity net gain work, so the application is ready when the report is.

Reports age. Professional guidance from <a href="https://cieem.net/resource/advice-note-on-the-lifespan-of-ecological-reports-and-surveys/" target="_blank" rel="noopener">CIEEM</a> treats reports over 18 months old as needing review, so a long gap between survey and decision can mean an update visit, again in season.

See what each survey costs in our cost guide.

Questions about timing

What happens if I miss the bat survey season?

Emergence surveys wait until the following May. In the meantime the preliminary roost assessment can be done, so the summer visits can be booked as soon as diaries open. Some councils will hold an application while seasonal surveys are completed; ask your planning officer.

Why can’t newt water samples be taken in July?

The eDNA method is only accepted for samples taken between 15 April and 30 June, when newts are in the ponds to breed (Natural Resources Wales). Outside that window, district level licensing can be an alternative in many parts of England.

Which surveys can I book in winter?

A preliminary ecological appraisal, a bat roost assessment and a badger survey. Use the winter to get these done and to book the spring and summer visits.

Does weather affect the dates?

Yes. Bat surveys need mild, dry and calm evenings, and reptile checks need warm but not hot days, so a wet or cold spell can push visits back.

Where our information comes from

Tell us about the site

Three short steps: where the site is, what you are planning, and how to reach you. About two minutes. If the council named a survey in a letter or validation checklist, choose that one.

Step 1 of 3

Where is the site?

Postcode