Very rare passage migrant

One was in a Pin Green garden on 29 September 2019.

Very rare passage migrant, formerly a summer breeding visitor.

Hertfordshire is at the eastern edge of the Wood Warblers range in Britain, and Stevenage was one of their strongholds in the County in the late 1970’s, unfortunately they are now rare passage migrants. Nationally they have declined by 75%.

Recorded by Foster (1914) as, “rare and very local in big woods”. One was recorded at Stevenage on 17 April 1935.

In the 1960s they were recorded from: Box Wood (male from 7 to 31 May 1968); Monks Wood (two on 19 June 1966); Tilekiln Wood (three on 4 May 1968).

The 1970s records are: present in the 1973 breeding season at Box Wood; one at Tilekiln Wood on 25 June 1974; one at Watery Grove from 20 April to 8 May 1977; pair at Box Wood on 18 June 1978, where young birds were seen being fed on 20 June and a fledged youngster seen on 1 July 1978; five pairs at Watery Grove 1978, where a fledged youngster was seen on 1 July; male Watery Grove 6 May 1979; Box two Box Wood on 13 May 1979.

The records for the 1980s and 1990s are: pair at Box Wood July 1980; three at Box Wood on 18 May 1984; one at Box Wood 11 May 1985; one at Watery Grove 30 April 1988; singing male at Pryors Wood 7 May 1990; one singing at the Town Centre Gardens on 5 May 1993.

The 1973 Breeding Atlas considered breeding as possible from the tetrads covering Chesfield Park and Boxbury Farm. Gladwin (1986) recorded that less than four pairs nested annually in various woodlands around Knebworth and Stevenage. The 1992 Atlas considered breeding as probable from the tetrad covering Boxbury Farm and, possible from those covering Norton Green and, Bragbury End. None were recorded in the 2012 Atlas.

The most recent records are of three spring passage birds: one at Fairlands Valley Lakes on 17 April 2007; one at Fairlands Valley Lakes on 7 and 8 May 2015; a singing male at the Warren Springs Laboratory (GSK) on 8 April 2019.

Common summer visitor and passage migrant, with records of overwintering. 

The Chiffchaff is the earliest of our returning migrants, usually arriving during the middle of March. The earliest spring arrival date for Stevenage is 9 March 2020 at Fairlands Valley Park, the latest autumn date is 23 November 2023 at Fairlands Valley Lakes.

Chiffchaffs winter further north than other related species, wintering in the Mediterranean and northern Africa. A small number also winter in Britain, including in Hertfordshire, these are probably birds from the Continent. Winter records for Stevenage are: One at Shephall Way on 2 February 1975; one in November and December 1988; one in a Jackdaw Close garden on 6 February 2000; one in a Jackdaw Close garden on 24 and 26 December 2001; one at Fairlands Valley Lakes in January 2005; one at Great Ashby on 24 February 2008; one in a garden on 8 January 2009; one in the London Road, near the Stevenage Brook on 2 December 2009; one at Burghley Close on 28 February 2016; one at Fairlands Valley Lakes on 21 December 2019.

Breeding was confirmed from six of Stevenage’s tetrads in the 1973 Breeding Atlas, ten in the 1992 Atlas and, from two in the 2012 Atlas.

In 2018 a juvenile was recorded in Fairlands Valley Park.

The Common Bird Census at Watery Grove recorded them holding between one and seven breeding territories annually between 1972 and 1999 with, the exception of 1984 and 1991 when only their presence was recorded.

Most recorded in one location are, 12 in Box Wood on 1 September 1965 and, 20 heard calling in Box Wood on 4 April 1981.

Nine were ringed in Box Wood in 1978.

One of the sub-species, Siberian Chiffchaff (P.c.tristis) was heard and seen along the River Beane, Aston End on 20 December 2020.

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.