The song thrush is a familiar songbird of gardens and farmland throughout Britain. It is a little smaller than a blackbird but has a similar shape and build. It has brown upperparts with white underparts and a speckled breast.
Its song is highly distinctive as each phrase is repeated up to three times. The clarity of each note is also remarkably pure.
The song thrush feeds largely on worms and snails. Dry or frozen soil conditions result in worms withdrawing from the surface and becoming unavailable to thrushes. At such times, they rely more heavily on slugs and snails. Song thrushes have the habit of using a favourite stone as an anvil on which to break snail shells.
About half of adult thrushes that breed in Britain and two-thirds of juveniles, migrate in the autumn (1). Most birds that migrate from northern Britain move to Ireland.
There is some evidence that males and females over-winter in different areas with the females tending to travel furthest. Many of the song thrushes that are seen in this country in the winter will be visitors from Scandinavia.
Main Habitat(s): Essentially a bird of primary forest that has much undergrowth. Adapted to living in small woods, parkland, hedgerows and gardens.
The song thrush suffered a 55% overall decline in population between 1970 and 1998. Its decline in farmland habitats was more marked than that in woodland. One study estimated the reduction in numbers as being 73% in farmland and 49% in woodland between 1968 and 1993 (2).
The Song Thrush is a Priority Species in the UK BAP because of its population decline (3). It also appears on the 'Red List of Birds of Conservation Concern' (4). It is protected under the Wildlife and Countryside Act 1981.
A reliable estimate of the total population size in the region is not available but the species probably remains widespread throughout (5). Breeding song thrush has been chosen as a Regional Biodiversity Indicator to measure conservation objectives linked with hedgerows (6).
According to the North West Biodiversity Audit (7), the maximum population densities are around Barrow-in-Furness and the Kent estuary in Cumbria. Merseyside and north Cheshire are also areas with an abundance of this species.
In North Merseyside, song thrushes breed in 90% of the 2 km squares surveyed in 1997-99 and are absent only from the most built-up areas (8).
Song thrushes are found throughout most of the county but they have their highest concentration in West Lancashire and South Ribble and on the north Lancashire limestone. Their occurrence in strong numbers in North Lancashire may be related to the abundance of snails (and worms) in limestone areas.
The estimated population for Lancashire and North Merseyside is 3000 pairs.
Current factors affecting the species
The song thrush's decline has been linked to a very high level of mortality of young birds during their first winter. Recent research indicates that song thrushes may need to produce up to five broods per year in order to maintain their population level and that recent habitat changes have limited them to an average of 2-3 broods a year.
One of the most important changes has been the trend away from spring-sown cereals resulting in the loss of important bare earth foraging habitat in the spring. The loss of stubbles has had similar effects in winter.
In general, there has been a reduction in the number of mixed (arable/pastoral) farming enterprises and a spread of crop monocultures. For the song thrush, this has meant that suitable feeding habitat is less easy to find throughout the year.
During the breeding season (March to July) song thrushes need nest sites in dense hedgerow or shrub cover. Loss or over-management of hedgerows reduces the supply of suitable nest sites and exposes nests to predators.
The widescale application of molluscicides may lead to indirect poisoning or starvation during periods of severe drought or frost, when the song thrush's diet switches to slugs and snails.
There is evidence from various parts of the country that urban habitats (parks, gardens, etc.) are becoming relatively more important for this species than they have been previously. The trend towards 'wildlife friendly gardening' is a welcome one, therefore, with regard to the song thrush.
Current Action / Mechanisms
The RSPB and the BTO are currently undertaking research into the causes of song thrush declines. The RSPB has prepared a SAP and a plan for this species is in the UK BAP.
Countryside Stewardship has the potential to benefit this species if it encourages hedgerows to be planted and maintained well.
Advice is available to landowners in the form of an advisory sheet that the RSPB has produced. FWAG visit some Lancashire farms and can advise on whole Farm Biodiversity Action Plans.
The species is still sufficiently widespread and numerous to be monitored adequately by the Breeding Bird Survey. The local distribution has been surveyed by the Lancashire Bird Club during 1997-1999 and the estimate of current population size given above is based on their data. A postcard campaign was organised as part of the Biodiversity Action Plan process during 1999/2000 to highlight certain key species. The song thrush was included as a local BAP species and the public were encouraged to report sightings. The preliminary findings of this survey were reported in the Wildlife Trust magazine (Autumn 2000) (9). The most up-to-date results emerging from this initiative are shown on a distribution map included in this BAP.
The song thrush is one of the species of wild birds of farmland whose numbers will contribute to the national sustainability indicators announced by the DETR in 1999 (10).
Objectives, targets and proposed actions for song thrush in Lancashire
References & additional reading:
1. Simms, E. (1978) British Thrushes. New Naturalist No. 63. Collins, London.
2. Fuller, R. J. et al (1995) Population declines and range contractions among lowland farmland birds in Britain. Conservation Biology 9.
3. UK Biodiversity Steering Group (1995) Biodiversity: The UK Steering Group Report. Volume 2: Action Plans. SAP for Song Thrush p.107. HMSO.
4. RSPB (1996) Birds of conservation concern in the United Kingdom, Channel Islands and Isle of Man. RSPB, Sandy.
5. Regional Biodiversity Steering Group for North West England (1999) Wild about the North West - A biodiversity audit of North West England.
6. English Nature (1999) Sustainable Development & Regional Biodiversity Indicators for the North West. English Nature, Peterborough.
7. Regional Biodiversity Steering Group for North West England (1999) Wildl about the North West. A Biodiversity Audit of North West England.
8. Environmental Advisory Service (2000) Consultation Draft of the North Merseyside Biodiversity Action Plan. SAP for Song Thrush.
9. Rodman (2000) Recording Lancashire's Wildlife. Lapwing. Autumn/Winter 2000. The Wildlife Trust for Lancashire, Manchester and North Merseyside.
10. Department of Environment, Transport and the Regions (DETR) (1999) A better quality of life - a strategy for sustainable development in the UK. DETR.
Date: April 2001.