Plan surveys around the seasons, not the programme.
Survey windows and seasonal constraints for the species and habitats that most often drive programme on infrastructure projects. Select a species for notes and links to Natural England, NatureScot and NRW guidance.
This month
In season to survey
Sensitive periods
- Optimal survey
- Possible survey
- Works window
- Sensitive period
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| Species and activity | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Hibernation roost surveys | Jan: Optimal survey | Feb: Optimal survey | Mar: Possible survey | Apr: none | May: none | Jun: none | Jul: none | Aug: none | Sep: none | Oct: none | Nov: Possible survey | Dec: Optimal survey |
| Emergence and re-entry surveys | Jan: none | Feb: none | Mar: none | Apr: none | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Possible survey | Oct: none | Nov: none | Dec: none |
| Activity transects and static detectors | Jan: none | Feb: none | Mar: none | Apr: Optimal survey | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Optimal survey | Oct: Possible survey | Nov: none | Dec: none |
| Maternity season — avoid roost works | Jan: none | Feb: none | Mar: none | Apr: none | May: Sensitive period | Jun: Sensitive period | Jul: Sensitive period | Aug: Sensitive period | Sep: none | Oct: none | Nov: none | Dec: none |
| Hibernation — avoid roost works | Jan: Sensitive period | Feb: Sensitive period | Mar: Sensitive period | Apr: none | May: none | Jun: none | Jul: none | Aug: none | Sep: none | Oct: none | Nov: Sensitive period | Dec: Sensitive period |
Preliminary roost assessments and tree inspections can be done all year. Surveys for licence applications must be from the most recent appropriate season. | ||||||||||||
| eDNA pond sampling | Jan: none | Feb: none | Mar: none | Apr: Optimal survey | May: Optimal survey | Jun: Optimal survey | Jul: none | Aug: none | Sep: none | Oct: none | Nov: none | Dec: none |
| Population surveys (torch, trap, egg search) | Jan: none | Feb: none | Mar: Possible survey | Apr: Optimal survey | May: Optimal survey | Jun: Possible survey | Jul: none | Aug: none | Sep: none | Oct: none | Nov: none | Dec: none |
| Terrestrial capture and exclusion | Jan: none | Feb: none | Mar: Possible survey | Apr: Works window | May: Works window | Jun: Works window | Jul: Works window | Aug: Works window | Sep: Works window | Oct: Possible survey | Nov: none | Dec: none |
Population surveys need at least half the visits between mid-April and mid-May. eDNA samples are accepted between mid-April and the end of June. District level licensing may remove the need for site surveys in participating areas. | ||||||||||||
| Sett and activity surveys | Jan: Optimal survey | Feb: Optimal survey | Mar: Optimal survey | Apr: Optimal survey | May: Possible survey | Jun: Possible survey | Jul: Possible survey | Aug: Possible survey | Sep: Possible survey | Oct: Optimal survey | Nov: Optimal survey | Dec: Possible survey |
| Licensed sett closure window | Jan: none | Feb: none | Mar: none | Apr: none | May: none | Jun: none | Jul: Works window | Aug: Works window | Sep: Works window | Oct: Works window | Nov: Works window | Dec: none |
Surveys are possible all year but are easiest when vegetation is low. Sett interference needs a licence, normally granted for July to November outside the breeding season. | ||||||||||||
| Nest tube and box surveys | Jan: none | Feb: none | Mar: none | Apr: Possible survey | May: Possible survey | Jun: Possible survey | Jul: Possible survey | Aug: Optimal survey | Sep: Optimal survey | Oct: Optimal survey | Nov: Possible survey | Dec: none |
| Hibernation — avoid ground disturbance | Jan: Sensitive period | Feb: Sensitive period | Mar: Sensitive period | Apr: none | May: none | Jun: none | Jul: none | Aug: none | Sep: none | Oct: none | Nov: Sensitive period | Dec: Sensitive period |
Survey effort is scored by month, with late summer and autumn carrying the most weight. Habitat clearance is usually phased: above-ground vegetation in winter, ground clearance once animals are active. | ||||||||||||
| Field signs and holt surveys | Jan: Optimal survey | Feb: Optimal survey | Mar: Optimal survey | Apr: Optimal survey | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Optimal survey | Oct: Optimal survey | Nov: Optimal survey | Dec: Optimal survey |
Otters can breed at any time of year, so works near holts need assessment whatever the season. | ||||||||||||
| Presence and population surveys | Jan: none | Feb: none | Mar: Possible survey | Apr: Optimal survey | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Optimal survey | Oct: Possible survey | Nov: none | Dec: none |
| Displacement window | Jan: none | Feb: Works window | Mar: Works window | Apr: Works window | May: none | Jun: none | Jul: none | Aug: none | Sep: none | Oct: none | Nov: none | Dec: none |
Two survey visits are normally needed, one early and one late in the season. Displacement under licence is limited to the period before the breeding season. | ||||||||||||
| Presence surveys (licensed) | Jan: none | Feb: none | Mar: none | Apr: none | May: none | Jun: none | Jul: Optimal survey | Aug: Optimal survey | Sep: Optimal survey | Oct: none | Nov: none | Dec: none |
| Breeding — avoid in-channel works | Jan: Sensitive period | Feb: Sensitive period | Mar: Sensitive period | Apr: Sensitive period | May: Sensitive period | Jun: Sensitive period | Jul: none | Aug: none | Sep: none | Oct: Sensitive period | Nov: Sensitive period | Dec: Sensitive period |
Survey methods involving handling need a licence. | ||||||||||||
| Preferred in-channel works window | Jan: none | Feb: none | Mar: none | Apr: none | May: none | Jun: Works window | Jul: Works window | Aug: Works window | Sep: Works window | Oct: none | Nov: none | Dec: none |
| Salmonid spawning and incubation | Jan: Sensitive period | Feb: Sensitive period | Mar: Sensitive period | Apr: Sensitive period | May: Sensitive period | Jun: none | Jul: none | Aug: none | Sep: none | Oct: Sensitive period | Nov: Sensitive period | Dec: Sensitive period |
| Coarse fish spawning | Jan: none | Feb: none | Mar: Sensitive period | Apr: Sensitive period | May: Sensitive period | Jun: Sensitive period | Jul: none | Aug: none | Sep: none | Oct: none | Nov: none | Dec: none |
Windows vary by river and species. Confirm with the Environment Agency, NRW or SEPA, which may set dates in permit conditions. | ||||||||||||
| Breeding bird surveys | Jan: none | Feb: none | Mar: Possible survey | Apr: Optimal survey | May: Optimal survey | Jun: Optimal survey | Jul: Possible survey | Aug: none | Sep: none | Oct: none | Nov: none | Dec: none |
| Nesting season — vegetation clearance constraint | Jan: none | Feb: none | Mar: Sensitive period | Apr: Sensitive period | May: Sensitive period | Jun: Sensitive period | Jul: Sensitive period | Aug: Sensitive period | Sep: none | Oct: none | Nov: none | Dec: none |
Active nests are protected whatever the date. Clearance in the nesting season needs a pre-clearance check by an ecologist. | ||||||||||||
| Wintering and passage bird surveys | Jan: Optimal survey | Feb: Optimal survey | Mar: Possible survey | Apr: none | May: none | Jun: none | Jul: none | Aug: none | Sep: none | Oct: Possible survey | Nov: Optimal survey | Dec: Optimal survey |
Relevant near SPAs, estuaries and functionally linked land. | ||||||||||||
| Presence and population surveys | Jan: none | Feb: none | Mar: Possible survey | Apr: Optimal survey | May: Optimal survey | Jun: Possible survey | Jul: Possible survey | Aug: Possible survey | Sep: Optimal survey | Oct: Possible survey | Nov: none | Dec: none |
| Translocation and exclusion window | Jan: none | Feb: none | Mar: none | Apr: Works window | May: Works window | Jun: Works window | Jul: Works window | Aug: Works window | Sep: Works window | Oct: none | Nov: none | Dec: none |
Surveys depend on weather. Avoid hot middays and cold, wet days. | ||||||||||||
| UKHab, NVC and hedgerow surveys | Jan: none | Feb: none | Mar: none | Apr: Possible survey | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Possible survey | Oct: Possible survey | Nov: none | Dec: none |
| Biodiversity net gain condition assessment | Jan: none | Feb: none | Mar: none | Apr: Possible survey | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Possible survey | Oct: none | Nov: none | Dec: none |
Out-of-season habitat surveys may under-record condition, which affects biodiversity net gain calculations. | ||||||||||||
| Terrestrial and aquatic invertebrate surveys | Jan: none | Feb: none | Mar: none | Apr: Optimal survey | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Optimal survey | Oct: none | Nov: none | Dec: none |
Timing depends on the target groups. | ||||||||||||
| Japanese knotweed and other INNS surveys | Jan: none | Feb: none | Mar: none | Apr: Possible survey | May: Optimal survey | Jun: Optimal survey | Jul: Optimal survey | Aug: Optimal survey | Sep: Optimal survey | Oct: Possible survey | Nov: none | Dec: none |
Most species are easiest to identify in the growing season. Knotweed canes remain visible in winter. | ||||||||||||
Indicative windows for lowland England and Wales. Seasons shift with weather, altitude and latitude, and typically run later in Scotland and upland areas. Always confirm against the current species guidance, the relevant good practice guidelines (for example CIEEM and the Bat Conservation Trust) and your licensing ecologist before fixing a programme.