Lost in the woods

UK Priority Species: Wood Warbler 

What makes the wood warbler so cool?
Wood warblers are revealing birds, divulging their secrets to the patient, quiet watcher. They will allow you to get quite close to them and even sing to you whilst you do! The shivering call, described as the woodland sound like no other, is made up of a rapidly accelerating metallic trill interspersed with melancholy whistles. The distinctive bugle has been likened to the sound of a coin spinning on a marble tabletop. Depicted divinely by naturalist W.H. Hudson as, ‘a voice that has light and shade, rising and passing like the wind, changing as it flows and quivering like a wind-fluttered leaf.’ Captivated? Totally.

Woodlands enrich our lives and provide us with essential life supporting systems.
I saw in the papers recently that a study by the woodland trust has found that only 15% of people in the UK have access to a reasonable sized wood near their house. What a shame! But, if you're one of those 15% then you should feel very proud and damn lucky. Otherwise, you might want to start organising a day trip to get to one. Woodlands are a haven, offering a beautiful way to relax, with gorgeous plays of light and colours, interesting insects and awe-inspiring trees.

However, if you go down to the woods today your in for a big surprise!
They’re rather quiet… Woodland birds have been one of the main groups of birds to be suffering steep declines, with migrant species, such as the wood warbler experiencing an alarming 60-70% decline. The most recent review of UK bird species placed seven woodland birds on the red list and nine on the amber list of conservation concern. Mounting evidence suggests that British woodlands and their management are changing in a range of ways that may have implications for the habitat and food resources that birds depend on. However, there are a number of possible reasons for these declines and we are now just beginning to understand their relative importance.

Breaking news just in!
I was lucky enough to have a chat with John Mallord one of our very own conservation scientists on the front line in the research into wood warblers, who has kindly supplied these great pictures, which really capture the personality of these lovely birds. John and the team have been undertaking research into these gorgeous birds in the beautiful oak woodlands of Wales, focusing on the dramatic Dinas RSPB Reserve. In order to enable a comparison between the habitat, breeding ecology and invertebrate mass at the site, present research has repeated a study carried out in the 1980s. This research aims to provide us with some answers as to why these birds are declining.

From steamy African tropical jungle to rolling Welsh oak woodland!
The complexity of the problems causing woodland bird declines has meant that finding out precise factors has been difficult. There are several theories which have been expounded for wood warblers. Wood warblers are long distance summer migrant birds, journeying to wintering grounds in sub-saharan Africa. It is hard to know whether the causes of these declines are occurring here in the UK, in sub-Saharan Africa or on the migration route. Climate change has been an increasing concern for migrating species as fears that movements in suitable climate space and changes in the timings of seasons will be difficult for migrants to follow. Research in the UK has been looking at whether these seasonal changes have been causing earlier peaks in invertebrate numbers, which migrant species are not able to arrive in time for. Another possible problem that was identified from analysis of breeding woodland bird data by RSPB scientists shows that growth of the understorey of the woodland has changed the vegetation structure, making it less suitable for wood warblers. This work is ongoing but it might mean we can suggest suitable grazing regimes for the the woodlands to keep this in check. 

Bucket loads of bugs?
The invertebrate survey has been undertaken using water traps, whereby invertebrates simply fall from the vegetation into the water and the researchers collect them. Last year five traps (actually cat litter trays) were placed in each of 16 woods throughout the summer and emptied of their contents every week. Only samples from six woods have been analysed but these have already produced in excess of 70,000 invertebrates. Quite the exhausting job! This painstaking work has not yet been analysed but due to my good fortune on being able to get the frontline information from John, there have been some preliminary patterns emerging. Surprisingly then, that I should hear that the total of 70,000 inverts is actually less in absolute numbers than there should be! Especially caterpillars, which are the delight of the wood warblers. However, despite climate change fears the invertebrate peak has been found to occur at the same time as it has previously, and coincided with the hatching of wood warbler chicks.

Something to warble about
Importantly the reduction in overall bug numbers has not seemingly impacted upon the wood warblers currently at this site and they are doing really well! The chicks are apparently strong, there was a good fledging rate and the population was healthy. Really positive news for us wood warbler fans! Another positive finding was that some birds, which had been ringed last year, had returned to the same site showing faithfulness for the location.

What you can do to make a difference in the International Year of Biodiversity!

The Migrants in Africa project, run by the RSPB, BTO, GWS and Naturama, is investigating the decline of many of our summer migrants in African countries like Ghana & Burkhina Faso in order to try and discern if there are conservation issues affecting our migrants species on their wintering grounds. This is really important work and has far reaching implications for many UK species. Have a look here for more information. If you would like to help us help wood warblers and enable research into their declines visit www. rspb.org.uk to find out how you can get involved. The RSPB could not exist without its supporters and members. We have achieved a great deal since our small beginnings in 1889, but there is still so much to do, and therefore - we need your help! Today over a million people are members of the RSPB, and many more support us in other ways. Will you join them?

What about a wood warbler walk in Wales?
When spring rolls around next year why not plan a visit to see the jewel of the woodland crown? Gwenffrwd valley, where the wood warblers roam along with other woodland delights such as redstarts, is a gorgeous part of Wales. Strolling through the old oak woodlands crossed with roaring river torrents, in April to May is a glorious experience and well worth the trip. And maybe, if you’re lucky, the wood warbler will let you in on a secret!