Willow Warbler (Phylloscopus trochilus)Where and when to see it in the UK
Status not yet classified · reporting peaks April to May · Leaf Warblers · BOU category A
Peak months
Contains OS data © Crown copyright and database right 2026 (grid squares, place names from OS Open Names). Northern Ireland place names: OSNI Open Data, OGL v3.0. County and country boundaries: Office for National Statistics, Open Government Licence v3.0. Coastline: Natural Earth. Bird records from the data partners listed here.
Willow Warbler has been recorded in 2,745 of the 2,971 10 km squares covering UK land (92%) in records to 2026. Its strongest squares are in England, Scotland and Wales. Reporting peaks in April to May.
Conservation status: Least Concern (IUCN Red List, LC)
View on the IUCN Red List- Very high
- 38% or more of visits
- High
- 18% to 38%
- Moderate
- 7% to 18%
- Low
- under 7%
- Surveyed, not recorded
- at least 20 qualifying visits, no record
- Insufficient records
- too few visits to say
- Lighter fill
- Few visits, lower confidence
- Small dot
- Occasional: a single record, or out of season
Relative to this species' best squares (how classes are calculated)
Seasonality
| Month | Relative to peak | Share of visits | Typical class |
|---|---|---|---|
| January | 0% | <1% | Very high |
| February | 0% | <1% | Very high |
| March | 4% | <1% | Low |
| April | 98% | 23% | Very high |
| May | 100% | 24% | Very high |
| June | 70% | 17% | Very high |
| July | 34% | 8% | Low |
| August | 65% | 15% | Moderate |
| September | 31% | 7% | Low |
| October | 5% | 1% | Low |
| November | 0% | <1% | Very high |
| December | 0% | <1% | Very high |
Squares with the highest reporting rate in April
| Square | Where | Share of visits | Class |
|---|---|---|---|
| C60 | Causeway Coast and Glens, Northern Ireland | 100% | Very high |
| C81 | Causeway Coast and Glens, Northern Ireland | 100% | Very high |
| D21 | Mid and East Antrim, Northern Ireland | 100% | Very high |
| D23 | Causeway Coast and Glens, Northern Ireland | 100% | Very high |
| D31 | Mid and East Antrim, Northern Ireland | 100% | Very high |
| H05 | Fermanagh and Omagh, Northern Ireland | 100% | Very high |
| H14 | Fermanagh and Omagh, Northern Ireland | 100% | Very high |
| H18 | Derry City and Strabane, Northern Ireland | 100% | Very high |
| H23 | Fermanagh and Omagh, Northern Ireland | 100% | Very high |
| H84 | Armagh City, Banbridge and Craigavon, Northern Ireland | 100% | Very high |