Comprehensive woodland bird survey

Results of the most comprehensive survey of woodland birds for over 20 years were unveiled, Monday 20 March, by Biodiversity Minister Jim Knight, with some important findings.

The Repeat Woodland Bird Survey was published by the Royal Society for the Protection of Birds (RSPB) and the British Trust for Ornithology (BTO). Among its key findings the report highlights the winners and losers of the bird population amid our changing landscape and climate.

All in all 11 out of the 34 species showed large national increases in numbers (greater than 25%), while 8 showed large decreases (greater than 25%). (Full details by species follows at Annex A.)

However one of the most worrying trends was the decline in long distance migrants, confirmed for the first time in this survey. Birds such as the tree pipit and spotted flycatcher showed declines of up to 70% in some areas.

Among residents and mid-distance migrants there were some unexpected success stories with continued growth of more common birds such as coal, blue and great tits. But concern continues to grow for their rare cousin the willow tit, which showed a decline of over 70% in some areas.

Similarly, while green and greater spotted woodpeckers show a substantial increase of over 200% in some locations, lesser spotted woodpeckers were down 59%.

Jim Knight said: “Woodland birds are a vital part of our natural heritage and while some of the birds featured in this report are familiar to us from back gardens and parks across the country, others like the willow tit and tree pipit are less common and becoming rarer. This report gives us clear scientific evidence for these changes.

“This survey not only tells us about the species themselves, but is a useful indicator of wider biodiversity issues within our countryside, that are impacting on our birds. I am pleased to hear that the Woodland Bird Group partners will be looking into the survey results to see how it can inform other areas of work, and allow further research and measures to help protect those species under threat.”

The research was commissioned and funded by Defra, the forestry Commission, RSPB, BTO, the Woodland Trust and English Nature. It was carried out with the support of the UK Woodland Bird Group – a forum that brings together a wide range of organisations concerned about the issue.

The study covered 406 woodland sites, and uniquely allows data comparison with similar surveys carried out in the 1960s, 1970s and 1980s. This enables the development of a comprehensive picture of the status and health of our woodland bird diversity, and to analyse trends and developing concerns. It also establishes a comprehensive benchmark for woodland bird population research. This is important because wild bird populations are one of the Government’s 15 headline indicators of sustainable development.

The research also sought to investigate whether national regular monitoring for woodland birds is reliable; look for evidence of habitat changes, or other factors which may affect bird populations; and to examine these in relation to some of the hypotheses currently put forward for the cause of woodland bird decline.

In recent years there has been growing concern about declines in woodland bird populations with the UK Government Wildbird Population Framework Indicator falling by 20% between 1976 – 2001. The reverse of the long-term decline in the numbers of woodland birds is one of the key objectives of the UK Biodiversity Action Plan.

Rob Fuller of the BTO, one of the co-authors of the report, said:

“This unique and detailed study complements the findings of our regular monitoring systems by providing a more in-depth examination of what is happening to our bird populations within woodlands.

We were not surprised that the study confirmed that large declines have occurred in certain resident species, notably willow tit, lesser spotted woodpecker and hawfinch. However, the declines in those summer visitors that spend the winter in Africa were more serious than we were expecting. At the same time it has been reassuring to see that several species are thriving in woodlands, such as chiffchaffs, blackcaps, great tits and coal tits.

The results of the study will be presented at a forthcoming conference on woodland birds in Leicester where several of the issues that may be involved in these population changes will be examined in detail.”

Report co-author Ken Smith of the RSPB added: “These findings are very valuable in helping to narrow down the possible causes of woodland bird changes but further discussion and research will be needed to explore the real factors at work here. As always with natural populations, one problem we have is that habitat changes can lead to a huge boost in numbers of some species, but those same changes could be making life harder for others.

“The challenge that lies ahead for us now is to take forward the most appropriate actions to help those species in dangerous decline, to make sure they are around for future generations to see in our woodlands and across our countryside.”

Other important findings include:

· The 8 species (out of a total 34) showing national declines (greater than 25%) according to the data were: garden warbler, lesser redpoll, lesser spotted woodpecker, spotted flycatcher, tree pipit, willow tit, willow warbler and wood warbler. Additionally, hawfinch showed a large decline based on the data from the RSPB survey sites and a moderate (less than 25%) decline according to the sites surveyed by BTO researchers.

· The 11 species showing large national increases (greater than 25%) were: blackcap, blue tit, chiffchaff, coal tit, great spotted woodpecker, great tit, green woodpecker, goldcrest, robin, treecreeper and wren.

· The report highlights a big decline in the numbers of long distance migrant birds, which could be due to a number of different factors both here, in their wintering areas and on their journeys. Among the declining species are: garden warbler, pied flycatcher, redstart, spotted flycatcher, tree pipit, willow warbler, wood warbler.

· The report also highlights some resident species in decline: especially the hawfinch, jay, lesser spotted woodpecker, lesser redpoll and willow tit.

· Differences across Great Britain:
- In Scotland the willow warbler showed increases compared with declines elsewhere in England and Wales;
- The garden warbler showed large increases in Scotland, whereas everywhere else (except the English West Midlands according to BTO sites surveyed) this species declined;
- Spotted flycatchers showed large increases in the South West region of England but generally declines everywhere else;
- Generally declines were greater in the south and east of Great Britain, rather than in the north and west, for a number of species;
- The Western Atlantic Oakwoods, which some have termed 'Britain's Rainforests', have a unique community of birds (wood warbler, tree pipit, redstart and pied flycatcher), two of which (tree pipit and wood warbler) have shown declines of over 50%.
· The report concludes that there is no over-arching hypothesis to explain the declines in woodland birds and a range of factors may be at work.

· Changes in woodland structure were thought to be one of the key drivers to some of the changes, although factors behind this are unclear. Possible areas of research to develop this further include looking at changes in woodland age, and active management of woodland, and for some specific species further research into the impact and increases in deer browsing, and for some species the impact of grey squirrel populations.