There was something magical about that first curlew of spring.

As I peered into the low morning sun, the bird's long legs and gently curving bill were outlined in silver. It picked its way elegantly across the field, probing into the grass, each blade tipped with shining dew. I could feel my heart thumping as I positioned myself behind a nearby hawthorn. They were back.

It was to be the first of many encounters with this secretive bird over the coming months. I was one of two staff working part-time on a pilot project to help curlew across the Upper Thames river valleys.

‘The loneliest voice that earth knows’
Curlew are our largest wader, and their sad, penetrating call was traditionally a sound of meadows across the countryside. Today they’re surprisingly hard to find. One of their lowland strongholds is the river valleys of Oxfordshire. Although numbers here have fallen by around 50% over the last ten years, over 40 pairs still return to their traditional sites every spring to breed.

My colleagues and I had been surveying numbers of curlew, amongst other waders, on farmland across the Upper Thames for many years, but we had precious little information about how successful they were at nesting and raising young.

In April a grant from TOE2 enabled us to start to gather much more detailed data on the breeding habits of these birds. We already knew which sites were likely to have curlew, so every week over the spring and summer, a small but dedicated team of volunteers carefully surveyed selected farms and nature reserves along the floodplain, recording the birds’ location, behaviour and key features of the local habitat.

Over March and April, the curlew were most easy to observe. Males and females would ‘hang out’ together in their favourite fields, regularly displaying in flight, their bubbling song accelerating through the open landscape. There were occasional tussles, apparently over mates or exact territory boundaries.

Ninja curlew
As May went on, they started to disappear. Birds were noticeably more edgy and skulking. On one site I monitored regularly, they used the deep ridge and furrow in their favourite field to move around like ninjas – constantly ducking out of view only to magically reappear elsewhere. It was a sign that the first eggs were being laid.

Following up these detailed observations from surveyors, licensed RSPB staff would spend hours in each field, waiting for that split second of behaviour that might reveal a nest site. The nest itself is no more than a lightly lined depression in the grass – sometimes in a grass tussock. Each precious egg is large, more pointed than a chicken egg, and grey-green with brown blotches. Quickly and carefully, we would place a fingernail-sized temperature sensor just beneath the nest, take a few measurements and then leave.

The temperature sensor takes a reading every few minutes, storing the data for up to ten days before overwriting with fresh information. Each nest therefore had to be checked every ten days to make sure we could retrieve the sensor once the nesting attempt was finished. By reading the data afterwards, we could tell when an incubating bird left the nest for a prolonged period of time, and the date and time at which the nesting attempt finished.

There’s always one...
Throughout all of this, there was a constant dialogue with the local farmers. As well as granting access for surveyors, they were an invaluable source of information on what their curlew were up to.

One Monday morning my mobile rang. It was one of the farmers that manage one of my regular sites. ‘You’ll never believe this,’ he said, ‘but I’ve found a curlew nest.’
‘That’s great,’ I exclaimed. ‘Thanks for letting me know – whereabouts is it?’
‘That’s the thing...’ he replied. ‘It’s in the maize stubble. I was going through it to put the next crop in, and the bird got up just in front of the tractor.’

There are very few records of curlew nesting in arable fields in the UK, so this was definitely not a scenario we had foreseen. When I visited, the farmer had kindly left an area uncultivated around the nest, but it looked worryingly exposed. A flock of rooks was following the freshly drilled maize seed nearby, and the eggs hadn’t a scrap of vegetation to conceal them. Nevertheless, there was nothing to do but take the initial readings and set it up with a temperature sensor.

I was disappointed but not surprised when the farmer called me back nine days later to say all the eggs had disappeared, and he’d retrieved the temperature sensor for me.

‘He guards the welfare of his own’
Elsewhere the long incubation period dragged on as the grass around us grew rapidly from ankle to knee-height. As liquid-eyed mayfly danced in the sun, most of our nests were being silently incubated by the hen curlew. I’d watch the male loiter nearby, head sometimes tilted to one side – watching the skies for danger. He reminded me of an expectant father pacing the hospital corridors. Occasionally a crow would fly too close to the nest site and only then would he mob it until it was out of the danger zone.

By the end of May, there were signs that some chicks had hatched. By mid-June it was all but impossible to detect new nests. In total we found eight curlew nests, of which we can be certain that at least three hatched. It was only when the chicks hatched that the parent birds become agitated by visitors, constantly calling and returning quickly to their young hidden in the buttercups or ragged robin. It’s incredibly difficult to follow chicks through long grass, but we have reason to believe some of the young fledged successfully.

After the birds had finished nesting and moved on, we took more measurements to try to understand why curlew nested in some fields, and fed in others. This included looking at the distance from field boundaries, vegetation height, density and composition. We also took soil samples and counted the main earthworm types – effectively picking through curlew left-overs!

Tomorrow’s curlew
As well as researching this local curlew population, the project is working with local farmers to actively improve conditions for the birds. Eight sites are being improved – including scrape creation and restoration - using the experienced contractors at R C Baker. Over the coming winter we plan to work on a further two farms.

We’ve also met up with the volunteer surveyors and farmers who were so central to this project. We wanted to share what we’d learned and hear their thoughts on what went well, and what might be done differently in future.

With this years’ fieldwork still being written up, it’s not yet certain what next spring will hold. If we are able to secure further funding, we very much hope to extend the fieldwork in 2017, using what we’ve learned this year and seeking to improve our sample size and ability to assess fledging success.

Field studies such as this are only the first step in helping our curlew. They will need a lot more concerted effort from conservationists and land managers alike if they are to continue to haunt our lowland meadows each spring.

None of this work would have been possible without the many farmers and surveyors involved. All of us are also grateful to the Trust for Oxfordshire’s Environment (TOE2) for their generosity and support for this project.