Nightingale

The Nightingale is very much a flagship species for the BTO. Since the last full survey in 1999, it has been the focus of a lot of our woodland research and specific issues such as the effects of deer browsing and habitat management.

Looking at the latest draft distribution map for Nightingale, prepared for Bird Atlas 2007-11, could be somewhat depressing, with major losses from even core counties such as Sussex. However, there are some glimmers of hope. The Nightingale is a species with particular needs and, where the right habitat is created, maintained and extended, things can get better.

Latest results

In the draft map that has been prepared for the new Atlas, solid triangles show recent changes, with black downwards-pointing ones indicating that the species was found in the ten-kilometre square in 1988-91 but not between 2008 and 2011. By contrast, orange upwards triangles indicate where it was found for the first time in the 2008-11 survey. Encouragingly, there are a few of these orange triangles for Nightingale, and further research could test whether these “new” areas have been managed with Nightingales in mind.

Open triangles remind us of previously-known changes. Black downwards-pointing ones indicate that the species was found in the ten-kilometre square in 1968-72 but not in the other two periods. Orange upward-pointing open triangles show squares in which birds were first found in 1998-91 and where they are still present.

In tabular form

1968-72 1988-91 2008-11
Dark salmon Present Present Present
Light salmon Present Not detected Present
Solid up triangle Not detected Not detected Present
Open up triangle Not detected Present Present
Solid down triangle Present Present Not detected
Open down triangle Present Not detected Not detected
History of change in breeding season occupancy from 1968 to 2011 

History of change in breeding season occupancy from 1968 to 2011

The last full Nightingale survey, back in 1999, showed that four counties accounted for over 70% of the singing males, with Sussex third at 15.4%. From the national map, there does not seem to have been a major change in Sussex but when one looks more closely there is a different story. 

An early map, prepared by John Newnham and Helen Crabtree for the forthcoming Sussex Atlas, shows the changes since their last breeding atlas (1988-1992) and indicates net losses of about one third. It appears that, even in the species’ heartland, we have lost many Nightingales.

Changes since the last Sussex breeding atlas (1988-1992)

Changes since the last Sussex breeding atlas (1988-1992)

This year’s survey

It may seem strange to be undertaking a full national survey of Nightingales so soon after a breeding Bird Atlas but we have specific questions we want to ask, some of which are listed here:

  • Habitat use: The 1999 survey recorded an increase in the use of scrub relative to woodland. Have scrub habitats continued to become increasingly important for the species. Do recent reports of colonisation of shelter belts within agricultural landscapes of Fenland indicate that further changes are taking place?
  • Water tables: Are damp areas an important and under-appreciated element of high quality Nightingale habitat – habitats that may be threatened by changing land-use and water extraction practises?
  • Bachelor birds: Since the 1999 survey, it has been learnt that birds that sing persistently at night, throughout the spring, are likely to be unpaired males. How does the ratio of paired to unpaired birds vary with habitat and position within the range? Are the places where we hear lots of birds actually not the places where the species breeds best?
  • Population: The adjusted count was 4410 singing males in 1999. What will it be in 2012 and how many pairs does this represent?

Nightingales turn up in new areas and information collected for Bird Atlas 2007-11 is helping us to target survey work for the 2012 survey. As well as asking volunteers to survey specific squares we should be delighted to receive reports of Nightingales via BirdTrack or on paper. 

Why are we losing Nightingales?

Simon Gillings, who is spending a lot of his time looking at Bird Atlas maps, and is thinking about the processes driving changes in bird distributions, commented, “Based on its observed climatic tolerances throughout the rest of Europe, and the manner in which climate is projected to change, some would expect Nightingales to spread into northern England and even southern Scotland, but we actually see the species contracting into the south-east.”

One of the key areas for future research is to try to understand the relative effects of climate and habitat change. Deer have already been implicated in the decline of Nightingales  and we know that species wintering in the moist tropical rainforest & Guinea Savannah, in countries running from The Gambia to Cameroon, have been faring relatively badly over the last few years.
For migrant species, such as Nightingale, habitat and climatic changes are operating in the UK, in Africa and at the refuelling stops they use whilst undertaking their marathon journeys. So, as well as studying Nightingales in England, we are doing the same in Africa.

As part of our joint project with RSPB and the Ghana Wildlife Service, Chris Hewson and the team have been studying Nightingales in scrubby patches within an agricultural patchwork of fields. These overgrown areas are lying fallow or may not be good for growing crops at all but they hold lots of ‘our’ European warblers and a good number of Nightingales. However, human population pressure means that these patches are disappearing from at least Ghana and possibly other areas of West Africa too. These semi-natural habitats are now very important to Nightingales as the more natural habitats they once occupied have now largely disappeared. 

Can we help?

So is there any sign of hope? Nightingales are well-known niche specialists; they like particular ages of coppiced woodland and a well-defined structure of scrubby thicket in which to set up their territories. These are both habitats that change quite rapidly. As coppiced trees get older they shade out plants such as bramble beneath them, leaving the ground-layer too open for secretive Nightingales, and the same sort of thing happens to scrub. To maintain Nightingales long-term, conservationists need to manage current Nightingale hot-spots to maintain the right mixture of ages of suitable habitat, using a mixture of coppice/scrub clearance and deer exclosures, and to find new ways to attract birds to new sites.

Conservation organisations managing scrub for Nightingales have a diagram in mind, based on detailed BTO research funded by Anglian Water, ten years ago. The sheltered hemisphere of green provides a damp microhabitat, bare ground for feeding and thick vegetation for the low-level nest. Land managers have taken this advice and the appearance of birds in new territories bears testament to their actions in support of Nightingales.
 

Habitat diagram based on detailed BTO research funded by Anglian Water

Habitat diagram based on detailed BTO research funded by Anglian Water

 A paper in the April 2012 issue of British Birds by BTO scientists Chas Holt, Chris Hewson & Rob Fuller provides a full summary of the status, ecology and conservation needs of Nightingales in Britain.

Graham Appleton