I am standing by a telescope on Upham Meadow and the Summer Leasow, 257 acres of wet grassland by the River Avon near its confluence with the Severn. This is said to be the largest hay meadow in Britain. With me are two energetic campaigners for Eurasian curlews, which are in headlong decline in the UK, and throughout their global range; BBC producer Mary Colwell, (check out her website http://www.curlewcall.org/), and Mike Smart of Gloucestershire Wildlife Trust.
The grass is not yet long enough to conceal birdlife; a scan of this vast flatland reveals fourteen curlews alongside several crows and lesser black-backed gulls. We are here to record their evocative songs and calls, to discuss ways of classifying what they mean, and how this can help with their conservation.
The grass is not yet long enough to conceal birdlife; a scan of this vast flatland reveals fourteen curlews alongside several crows and lesser black-backed gulls. We are here to record their evocative songs and calls, to discuss ways of classifying what they mean, and how this can help with their conservation.

Upham Meadow is too prone to flooding to have ever been improved; instead it hosts one of the main concentrations of breeding curlews in lowland Britain. Mike tells me that the meadow is still managed according to an ancient regime. It is divided into many strips owned by various local farmers; hay can be cut from June 15th, and must be cut by 4th August, Lammas day (an old harvest festival, named after the Anglo-saxon for loaf). Commoners from the local village can then graze livestock until the first winter flood - leasow is a verb meaning to graze or pasture. Traditionally the staggered timings of the hay cut on different strips maintained a perfect mosaic of long and short grass for young curlews and their invertebrate food; Natural England has negotiated an agreement with the farmers to perpetuate this. Public access is restricted in the breeding season.
Curlews are long lived, and each pair needs to produce 0.5 chicks a year to maintain the population. Sadly even in this island of apparently perfect habitat all is not well; the local group of about 30 pairs fledged only three young last year, and even in good years they are well behind the required rate. Foxes, badgers, crows and gulls have all increased rapidly, and will be on the look out for eggs and chicks when the time comes. Another change is that the M5 now crosses the meadow on an embankment and I soon realize that in the prevailing strong south-westerly my recording equipment will be completely redundant due to traffic noise.
Curlews are long lived, and each pair needs to produce 0.5 chicks a year to maintain the population. Sadly even in this island of apparently perfect habitat all is not well; the local group of about 30 pairs fledged only three young last year, and even in good years they are well behind the required rate. Foxes, badgers, crows and gulls have all increased rapidly, and will be on the look out for eggs and chicks when the time comes. Another change is that the M5 now crosses the meadow on an embankment and I soon realize that in the prevailing strong south-westerly my recording equipment will be completely redundant due to traffic noise.
The curlews are lounging around not appearing to do much. Occasionally a couple will rise up, their bubbling faintly audible above the roar of the motorway, and fly around the meadow, then settle and chase each other around with wings raised, before offering each other pieces of grass in a curious ritual which no-one has quite made sense of. There is still a lot to learn about curlews, and the race is on to understand them so that conservation measures can be put in place before it is too late. My job is to classify their vocalisations for use both in public engagement and specialized data collection.

Of all British birdsongs the curlew has a particular emotional appeal, evoking melancholy and ecstacy at the same time. Click here to listen to the high intensity song of a male. Why is it so memorable? Like most human music, and some other birdsongs, the curlew takes advantage of natural harmonics to create satisfying and far carrying vocalisations. Using its syrinx as we use a brass instrument, the curlew runs up the harmonic series to communicate excitement or alarm. The female will choose a male for the quality of the highest harmonic in his song; high harmonics are also used to show the threat of danger. Birds open and close their beaks and use their tongues to create smaller variations of pitch, in the same way as a trombonist uses his slide; any curlew vocalization slowed down to a quarter speed can easily be reproduced on a trombone. Click here to listen to the same song slowed down.
In addition to their song, curlews have a repertoire of calls, from the cheeping of unhatched chicks (curiously reminiscent of willow warbler song) to a variety of communications between adults, and between adults and chicks. I know a gamekeeper in Yorkshire who reckons he can tell at a mile's distance whether a curlew has seen a fox or a stoat. At least thirteen different vocalisation types have been identified; there are probably more, but I'll have to find somewhere quieter to record them.
In addition to their song, curlews have a repertoire of calls, from the cheeping of unhatched chicks (curiously reminiscent of willow warbler song) to a variety of communications between adults, and between adults and chicks. I know a gamekeeper in Yorkshire who reckons he can tell at a mile's distance whether a curlew has seen a fox or a stoat. At least thirteen different vocalisation types have been identified; there are probably more, but I'll have to find somewhere quieter to record them.
For an opportunity to learn more about curlews, and to observe and listen to them safely at close quarters, come to the Bolton Castle Curlew Festival in June.