Declining summer visitor and passage migrant.  

Willow Warblers are declining in south – east England whilst the reasons are not yet known it is suspected that there are problems in their wintering areas and, whilst on migration.

As an indication of how they were once quite numerous: 11 were seen at Holbrooks Farm, Aston on 24 May 1977; 51 were ringed at Box Wood in 1978; significant “falls” of around 30 passage birds recorded at Box Wood on 14 April 1979 and 20 to 30 birds on 12 April 1980; 138 were ringed at Box Wood in 1980.

The 1973 Breeding Atlas confirmed breeding from seven of Stevenage’s tetrads and, the 1992 Atlas from 10. The 2012 Atlas only considered breeding as probable from the tetrads covering Chesfield Park and, Boxbury Farm.

Fledged young were seen at Fairlands Valley Park on 15 August 2016 and a juvenile was seen at an unrecorded location in August 2021 near where a bird had been seen with nesting material earlier that year.

The earliest spring arrival date is 15 March 1967 at Astonbury, the latest departure date is 14 October 1976 at an unrecorded location.

As birds that nest on or near the ground, there is an unusual record from 1910 of a pair nesting in a nest box in a tree four feet from the ground in a “large wooded” garden in Stevenage.

The Common Bird Census at Watery Grove recorded them holding between one and fourteen breeding territories annually between 1972 and 1999, with the exception of 1993 and 1994 when only their presence was recorded. Having reached a peak of 14 territories in 1981 they averaged five territories during the remainder of the 1980s, and only two territories during the 1990s. They were also a species that was able to colonize the interior of the wood as a result of coppicing.

The most recent record for Stevenage is one at Fairlands Valley Lakes on 10 April 2026.