First UK snow bunting survey and population estimate

Blog post by Daniel Hayhow, Conservation Scientist, RSPB Centre for Conservation Science

Our understanding and knowledge about the UK’s breeding snow buntings dates back to between 1930 and 1950 when Desmond Nethersole-Thompson worked on the species for one of his fascinating monographs of birds of the Scottish Highlands.

The many hundreds of hours Nethersole-Thompson spent observing the minutiae of the lives of colour-ringed snow bunting pairs, which he named individually, on the tops of the highest mountains in Scotland is without comparison.

At that time it was thought there were fewer than 10 pairs breeding in Scotland. Over the decades, long-running studies of snow bunting breeding ecology and increased survey coverage and recording led to the consensus that by the 1990s there were between 70 and 100 pairs.

Yet all sites had never been surveyed in a single year and knowledge was still limited beyond their core breeding area of the Cairngorms.

The survey

In 2011 the RSPB/SNH Montane Survey was carried out, giving the opportunity to carry out a systematic survey of snow buntings for the first time, alongside the repeat survey of the main target species: dotterel.

Species specialists, the Rare Breeding Birds Panel (@ukrbbp) and fieldworkers came together to identify all known breeding locations for this arctic specialist since 1970. Locations varied in accuracy from specific nest sites to entire mountain ranges so the fieldwork was set to be challenging!

How did we do it?

RSPB Conservation Scientist, Andy Stanbury coordinated the fieldwork and tells us a bit about the task at hand:

“Fieldwork in the UK doesn’t come much more challenging than surveying our montane wildlife. During the summer, snow buntings are only found on our highest peaks, where they breed near the mountain tops in corries and often feed close to any retained patches of snow.

In 2011 the task set for the seven fieldworkers, including myself, with the invaluable help of many volunteers, was to check out as many of the current and former breeding sites across Scotland as possible. This entailed climbing as many 3000ft mountains in a day as possible. Although this certainly helped with my ‘Munro bagging’, I quickly learnt that my maximum was two!

Most of the Scottish snow buntings breed on a few ‘core’ sites, mostly our highest mountains. Elsewhere they are found very sporadically. It took two weeks, and over a dozen Munros bagged, before I recorded my first bird.

The Cairngorms are challenging place to survey for wildlife - even in summer!

Along the edge of a corrie I faintly picked up what I thought was a bit of song. It must have been 300m or so away, and the sound was carrying in the wind. Was it a real snow bunting or was it just my imagination running riot again? It can easily happen when, for weeks on end, you can’t see the species you are searching for!

As I approached I picked up a male singing sitting on a rock. Luckily, I wasn’t going mad. The bird quickly moved on and was gone. It was probably an unpaired male roaming around. That was the only snow bunting I saw or heard while roaming the mountains for six weeks. Thankfully, other surveyors had more luck.

Although it was physically and mentally challenging fieldwork, it was a pleasure to work in such spectacular landscapes. You do, however, need to be prepared for all weathers. I will always remember being caught in a blizzard on the tops in mid-June, around the longest day of the year.”

The fieldwork team, volunteers and full time fieldworkers alike covered an impressive 12,000 ha of montane habitat in 2011. Searching, watching and listening for signs of snow buntings amongst screes and corries.

How many snow buntings are there?

The paper explains the process of calculating the population estimate, taking into account the fact that in such conditions birds will inevitably be missed. By using repeated visits to a number of sites we are able to quantify such detection error and calculate an estimate of the population size.

Two population estimates were calculated; considering only records of territorial males the population would be estimated at 60 territories (95% CI = 48-83).

A slightly less conservative estimate calculated using all records of males in suitable habitat gives 99 territories (95% CI = 88–114). Neither of these are inconsistent with previous well informed ‘guestimates’.

For a scarce species occupying some of the harshest more remote habitats in the UK dedicated surveys such as this are likely to be the only way to monitor their populations effectively.

Why did we do it?

The importance of this paper is that it establishes a baseline, and a repeatable methodology and analytical approach to assess future change in the population.

The ability to detect changes in the size of the population will be key in understanding how the species responds to changes in the montane environment.

Why not read the full paper 'The first UK survey and population estimate of breeding Snow Bunting Plectrophenax nivalis'?

The 2011 Snow bunting Survey was carried out under the Statutory Conservation Agencies/RSPB Annual Breeding Bird Survey (SCARABBS) programme and was funded by the RSPB and SNH.