Press Releases - January/February 2005

Item 5

25 February 2005

Tough time for woodland birds

Birdwatchers have recently woken up to the crisis facing several woodland bird species. In a new review in British Birds, published on 1 March, ornithologists look at just how bad the situation is and suggest reasons for declines.

A new review, undertaken by the British Trust for Ornithology for the Joint Nature Conservation Committee (JNCC), the Government's wildlife advisory body, is published on 1 March in British Birds (note 2). The authors, Rob Fuller, David Noble and Des Vanhinsbergh (all of BTO) and Ken Smith of RSPB discuss the reasons for the woodland population declines of up to 85% for species such as Spotted Flycatcher (down 85%), Lesser Spotted Woodpecker (81%) and Lesser Whitethroat (79%). (See table at end of news release)

Having looked at a whole range of potential reasons for the declines, the following seven factors emerge as potentially affecting a wide suite of species.
· Pressures on migrants during migration or in winter
· Climate change on the breeding grounds – especially changes in the timing of insect food and the drying out of woodlands
· Reduction in numbers of insects and other invertebrates
· Impacts of land use on woodland edges and on habitats outside woodland
· Reduced management of lowland woodland
· Intensified habitat modification by deer – removing the understorey and stopping regeneration
· Changing predation pressure (Grey Squirrels, corvids and Great Spotted Woodpecker).
(see table at end of this news release for details of which species might be affected by which factor).

Dr Rob Fuller, Director of Habitats Research for the BTO, and an acknowledged expert in woodland research said: “The decline in farmland birds in the 1970s and 1980s was dramatic enough to be noticed by most people with an interest in birds and the countryside. For woodland birds, there has been a ‘decline by stealth’ as the numbers of about fifteen species have slipped away. Interestingly, the declines have occurred at a time when the area of woodland in Britain is increasing and attitudes amongst woodland managers appear to be more sympathetic than ever to woodland wildlife. In the case of farmland birds, the causes of declines lie mainly with the intensification of farming. However, no single process of this kind can be identified within woodland and we are only just starting to understand the ways in which this important habitat is changing.”

Dr Ken Smith, Head of Aquatic and Woodland Research at the RSPB and an expert on woodpeckers said: “Many of the organisations within the Woodland Bird Group have already instigated new research, to try to work out what is happening to woodland birds. For instance, CEH/EGI are working on the Marsh Tit and RSPB/EN/FC are now into the second year of a study of one of the most rapidly declining species – the Willow Tit. One of my particular concerns is for the Lesser Spotted Woodpecker and this year the RSPB are starting a pilot research project to understand why this species is in such steep decline.”

Dr David Stroud, the Senior Ornithologist for JNCC said: “We hope that this review receives a great deal of publicity and that concerned birdwatchers will want to get involved in the new Scarce Woodland Bird Survey, launched by BTO and JNCC this spring. Every sighting of species such as Hawfinch and Willow Tit is now of interest, providing valuable information about the habitats that specialist woodland birds require.”

Notes for editors

1. ‘Recent declines in populations of woodland birds in Britain: a review of possible causes’ is published in the March issue of British Birds. The authors are Rob Fuller, David Noble and Des Vanhinsbergh (all of BTO) and Ken Smith of RSPB.

2. British Birds (BB) is a monthly journal for all keen birdwatchers. Articles are published on a wide variety of topics, including behaviour, conservation, distribution, identification, status and taxonomy. Contributors include both professional and amateur ornithologists, and content is always abreast of current ideas and thinking, yet written in a clear and simple style which is easy to interpret. BB is regarded as the journal of record in Britain, and contains the annual reports of the Rarities Committee and the Rare Breeding Birds Panel. Visit the website: www.britishbirds.co.uk

3. Background: Large declines in the breeding populations and contractions of breeding range have occurred in several woodland birds in Britain in recent decades. Data from the BTO’s Common Birds Census indicate that 10 out of 32 woodland species declined by more than 50% between 1966 and 1999 while five species increased by more than 50% over the same period. The declining species differ substantially in their ecology and life history patterns. No single general explanation can be identified for the declines and it is very likely that multiple factors have exerted a combined effect on several of the species.

4. This review was undertaken mainly under the partnership between the British Trust for Ornithology and the Joint Nature Conservation Committee (JNCC). The JNCC is the forum through which the three country conservation agencies - the Countryside Council for Wales, English Nature and Scottish Natural Heritage - deliver their statutory responsibilities for Great Britain as a whole, and internationally. These responsibilities contribute to sustaining and enriching biological diversity, enhancing geological features and sustaining natural systems. As well as a source of advice and knowledge for the public, JNCC is the Government's wildlife adviser, providing guidance on the development of policies for, or affecting, nature conservation in GB or internationally. Website: www.jncc.gov.uk

5. Woodland bird population levels are monitored using the Breeding Bird Survey, with the help of over 2000 volunteers across the whole of the UK. The Breeding Bird Survey is a partnership of the BTO, JNCC and RSPB.

6. BTO, in partnership with the Joint Nature Conservation Committee, is launching a Scarce Woodland Bird Survey to produce better information on the habitats used by woodland birds. There are two parts to the survey: Woodland Walks where volunteers survey woodland birds in two woodlands, and Casual Records, which just involves keeping a list of the target birds seen between late March and end of June. For more information please talk to Su Gough, on 01842 750050, or visit www.bto.org/survey/special/scarce_wood_bs.htm

7. A table identifying the potential reasons for the decline of the 15 most vulnerable woodland species in this review follows these notes.

8. Images for use alongside this article are available free of charge from E-mail:

For further information please contact:

British Trust for Ornithology: Rob Fuller on 01842 750050 or e-mail: during office hours
Graham Appleton: 01842 750050 (work) 07974 668503(mobile) e-mail:

RSPB: Ken Smith on 01767 680551 during office hours

British Birds: Roger Riddington on 01950 460080 or e-mail: during office hours


Identifying the causes of declines

Summary of likely causes of population declines in woodland and scrub species in Britain. The strongest current hypotheses are stated in italics. Estimated change in population and distribution of woodland birds are mainly based on Common Birds Census woodland plots surveyed by BTO volunteers between 1966 and 2000. Reliable figures are not available for three of the species, using this methodology.

Capercaillie Collisions with deer fences. Nest predation. Changes in weather patterns. Both low breeding success and high mortality of fully-grown birds are implicated in the decline. The former appears to be a consequence of changing patterns of spring temperature and wet summers, coupled with high nest predation rates. High mortality is caused by collisions with deer fences.

Woodcock (61% decline) No strong hypothesis. Possible factors could include recreational disturbance (especially perhaps from dogs), modification of the field layer by deer and increasingly dry conditions within some woods as a result of climate change and surrounding land management.

Lesser Spotted Woodpecker (81% decline) Interactions with Great Spotted Woodpeckers. Changes in dead wood and dead wood invertebrates. This woodpecker depends critically on invertebrates in small diameter dead wood and it is possible that subtle changes may have occurred in this resource. Great Spotted Woodpeckers have been observed usurping Lesser Spotted nesting cavities and are also nest predators. Competition between these species has been suggested to occur in Sweden. Large home ranges suggest that landscape scale changes in tree abundance may be important.

Tree Pipit (75% decline) Changes in age structure of forests and woodland. Reduction in management in lowland woods. The overall extent of the population decline is not clear given the limited representativeness of the CBC index in the north. Habitat availability in the south may be an issue due (a) to reduction in the planting of conifers and hence reduction in extent of suitable young growth and (b) the trend towards less management in many woods, with consequent canopy closure.

Dunnock (58% decline) Changes in the woodland understorey. Canopy closure in the absence of woodland management and increased browsing pressure from deer are likely to have reduced habitat quality for the species in many lowland woods.

Nightingale Pressures on migration and in the winter range. Changes in habitat quantity and quality in the breeding areas. Habitat quality has declined locally as a consequence of succession, canopy-closure and deer browsing.

Song Thrush (48% decline) Drainage of damp areas outside woodland. Drying out of woodland. Changing understorey structure within woodland. The decline appears to be driven by reduced survival of birds in their first winter and possibly in the post-fledging period. Lack of invertebrate food on farmland as a result of drainage is important but dryness within woods may also be relevant. Canopy closure and deer browsing is likely to affect quality of woodland understorey vegetation for nesting.

Lesser Whitethroat (79% decline) Pressures during migration and in the winter range. The Lesser Whitethroat has been little studied in Britain. Locally, loss of tall thick hedgerows and reduction in suitable scrub habitats, especially through successional change, may have been important. Habitat changes within woodland are unlikely to be important as the species seldom uses true woodland habitats, even coppice.

Willow Warbler (53% decline) Pressures during migration and in the winter range. Reduction in habitat quality on the breeding grounds. Survival rates were reduced in the period of decline and there has been a moderate increase in the rate of nest failures. Two factors likely to be at least of local significance in southern Britain are: (1) successional changes in scrub habitats, (2) deterioration in availability and quality of young-growth woodland habitats as a consequence of reduced woodland management and deer.

Spotted Flycatcher (85% decline) Pressures during migration and in the winter range. Reduction in invertebrate food supplies, particularly large flying insects. Breeding performance has not declined over the last two decades but first year survival has. This may be the result of changes in conditions outside Britain, or a consequence of deteriorating habitat conditions and food availability in the post-fledging period in Britain, or both. Spotted Flycatchers have declined in other European countries, suggesting a mechanism operating outside Europe.

Marsh Tit (68% decline) Reduction in structural and floristic diversity. For year-round feeding, a diversity of seed-bearing trees and shrubs appears to be important to this species, as well as areas of well-developed undergrowth. Habitat quality is likely to have been adversely affected both by reduction in broadleaved woodland management and by increasing pressure from deer.

Willow Tit (74% decline) Competition with other tit species. Predation from Great Spotted Woodpeckers. Changes in quality of woodland feeding habitat. Great and Blue Tits have been recorded usurping Willow Tits from next cavities. Nesting Willow Tits may be especially vulnerable to woodpecker attack because nests are typically excavated in soft wood. Changing woodland habitats, arising through increased canopy closure and intensified deer browsing, may be reducing food supplies.

Lesser Redpoll (78% decline) Changes in age structure of forests and woodland. In southern Britain, reduction in the planting of conifers and hence reduction in extent of suitable young growth may be important. In the north, however, the extent of population change is unclear because the CBC index is not representative of habitats there. There is some evidence that survival was reduced during periods of population decline.

Bullfinch (38% decline) No strong hypothesis. Causes of decline in the Bullfinch are not understood. However, the most likely explanation relates to reduction in habitat quality, possibly at the woodland edge, or more widely in the surrounding landscape. Reduction in woodland management, leading to canopy closure, and increased pressure from deer may have caused a reduction in food supplies through loss of plant diversity and reduction of the understorey.

Hawfinch Nest predation. There is little hard evidence but increased nest predation by Grey Squirrels and corvids seems a likely cause of the decline. Little is known about changes in availability

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