I’ve written a fair few spring-related articles over the years, each one pondering the various signs that herald the end of winter. And while I’ve always reasoned that spring is a culmination of numerous natural cues across a period of weeks, if I was forced to single-out one thing that represents spring more than any other, then it would be the return of the curlew.
Appearance wise, the curlew is surely a contender for our most recognisable bird silhouette. Large, with long legs and a long neck, a small head, and a long and thin beak that curves downwards.
That beak is its defining physical characteristic, and is represented by both parts of its scientific name, Numenius arquata. The first word derives from two Greek words meaning ‘new moon’, while the second is from the Latin word for ‘bow-shaped’.
The curlew is our largest wading bird (or wader) – almost 60cm long, with an impressive wingspan of almost one metre. To the eyes, it’s a striking creature, but to the ears it is something else.
Liquid smooth
For me, the curlew is the audio embodiment of the outdoors at this time of year. I attribute this association to being an enthusiastic hillwalker, because in Scotland that means you likely spend your weekends tying bootlaces in the kinds of places where curlews like to hang out – rural, away from human bustle, on the rough and wet grassland that guards the approaches to our high hills and glens.
When I play the sounds of the curlew in my head, they’re always a bit distant. They’re not sharp sounds uttered within 10 metres of me, like songbirds in a nearby tree. They’re soft, muted, perhaps 100, 200, even 500 metres away, which is indicative of how flighty and wary curlews generally are of humans.
Distant and soft though those sounds might be, the curlew’s voice is clean enough, its pitch high enough, to cut through the breeze and travel great distances.
The first familiar voice is its simple call. Two notes, the first low, the second high, with the emphasis on the second one. It often gets written as:
Cur-LEE. Cur-LEE!
Curiously, in France the curlew is called ‘courlis’, which is very similar to the phonetic ‘cur-lee’, suggesting onomatopoeia being used for its name. But it’s the curlew’s song that is most ear-catching, and instantly recognisable. Nothing else sounds like it.
It begins with several low (and slow) identical whistles, each one rising in pitch ever so slightly. You often see this written as ‘Whaup…..whaup….whaup…..’ which is actually a Scots name for the curlew.
I couldn’t find anything conclusive online to suggest that ‘whaup’ is an onomatopoeia, but seeing as it perfectly describes the sound, I’d love to believe that the Scots, like the French, named it to imitate the curlew’s voice.
Anyway, these initial whaups then become more urgent, the pitch and speed rising, before the whistles erupt into a warble-like trill. This bubbles away beautifully while the pitch slowly descends again, gently winding-down before stopping.
Like so many others before me, I find myself employing liquid language to describe the curlew’s song: fluid, smooth, rippling, bubbling. But however you describe it, the curlew’s song is weirdly soothing. I simply can’t imagine being in a stressful situation, listening to it.
The song is typically accompanied by a slow, undulating display flight, which the birds use to attract a mate and mark their territories. Watching curlews in the Lomond Hills, the ‘whaups’ seem to be uttered while the bird is rising or gliding, and then the more agitated part of the song occurs on the descent.
The first time I heard that song this season was outside my home in Braemar, on 9th March. It was lovely to have them back. But where had the curlews been before then? And why do they come here?
Winter
Curlews spend winter on the mudflats, salt marshes and fields around the UK coastline, where the weather is generally milder and the prey is more readily available. Unlike inland, the intertidal zone, between the high and low tide marks, remains unfrozen and soft throughout the winter. Perfect for foraging.
Some curlew do leave these shores completely in winter, going to even milder places like Ireland or France, while many curlews from colder climes than ours (Scandinavia and the Baltic), seek winter refuge here.
But this is where that beak comes into its own – probing the soft ground for snails, crabs, shrimp and shellfish. All waders probe with their beaks, of course, so what makes the curlew’s beak different?
A curved bill can get into more of those hard-to-reach places than a straight bill can: around and under stones, or in complex crab burrows with multiple chambers or tunnels.
A curved beak also enables the curlew to explore sideways underground, in a more 3-dimensional way, with just a small tilt of its head. This gives it a greater chance of detecting and catching prey than would be possible if it had just a straight beak to explore burrows and cavities.
Like many other waders, the tip of the curlew’s beak is covered with nerve endings, sensory receptors, which enables them to detect prey underground without seeing it. The very tip of the beak is also able to flex and open without the curlew opening its mouth (called rhynchokinesis), which means it can use the tip of its beak like tweezers underground.
Location location location
In spring, curlews head inland to breed. They like open, tussocky ground with a mix of vegetation heights – dry areas for nesting, but within reach of wet areas for foraging.
Vegetation, such as rushes, needs to be dense enough to conceal a nest, but open enough to allow ease of movement. When the chicks hatch out, they need a variety of readily available invertebrate prey, for which they like to forage out of sight.
Curlews like to be away from human disturbance, and obviously want to be away from predators, so they will keep well away from trees, woodland and scrub.
Suitable breeding habitat for curlews used to be much more extensive than it is now, and included traditional hay meadows, but these days it tends to mean upland heath, bogs and wet grassland where shrub and tree cover is largely absent. Marginal, invertebrate-rich pasture, where earthworms, larvae, spiders, beetles etc are plentiful.
This kind of habitat might look wild or unkempt to the casual observer, but it’s often described as ‘semi-natural’ on account of it having been managed or grazed historically, albeit non-intensively. For as much as curlews might like to avoid humans, they like places where humans actively manage the landscape in this ‘semi natural’ way. Such habitats exist as a result of mowing or cutting or grazing, and this highlights how important farming and crofting are to the survival of certain species.
Once the curlews arrive back, the singing begins. I’ve been fortunate to spend many years on a farm that had breeding curlews, and those first whaups and liquid trills on a chilly Fife evening, with cold east winds blowing, were annual events I’d always savour. So much so that I recorded the date for a few years.
2022 – 27th February
2021 – 26th February
2020 – 19th March
2019 – 22nd February
2018 – 20th March
2016 – 19th March
2015 – 21st March
The curlew’s return to the Lomond Hills was interesting, because it seemed to cluster around two distinct periods – the end third of February, and the end third of March. I assume the groupings were weather and/or food related but couldn’t say for sure.
There were also some confusing years when I heard curlews calling out in the hills in autumn, or in mid-winter, which always baffled me until I realised that it was the local resident starlings playing the fool. Our starlings, having spent every spring mingling with the curlew, had long incorporated elements of its song into their own repertoire, and doubtless passed it down through the generations.
Speaking of generations, curlew are loyal to their previous breeding areas, and to their mates. They tend to return to the same sites, and pair up with the same bird.
Into April
By now, the curlew will have reestablished their mating pairs and will be making their nests. Curlews are ground nesters, laying their eggs in a simple ‘scrape’, which is essentially just a shallow depression smoothed out of the grass.
They are understandably secretive about the location of their nests. When returning, they are careful to land well away from the nest before walking up to it, which helps conceal its location.
In late April/early May they lay (typically four) greeny-brown, speckled eggs. These are then incubated for four weeks, with hatching occurring in May-June. When the chicks hatch, their eyes are open and they are mobile. They and the adults quickly leave the nest, and roam freely thereafter.
Chicks’ beaks are small and straight, so they forage for invertebrates on the ground surface at first, which is why breeding areas need to have a good food source. The adult female tends to leave shortly after the chicks hatch, leaving the male to rear them until they fledge (fly), which happens around five weeks after hatching.
Come July/August, the curlews have all migrated away again, and the fields again fall silent. Hopefully that beautiful song returns the following year but, these days, things are rather precarious.
Decline
As familiar as the curlew’s song might be, for many people in the UK it’s something that is familiar only through nostalgia – it’s a sound from their childhood, rather than being a sound from their present.
It’s quite normal, when folk are discussing curlew on a social media post, to see comments like “love this sound. Used to hear it where I grew up”.
“I remember hearing curlew in the fields behind the house. But they’ve not been there for years now”.
The UK is a global hotspot for the curlew. 140,000 of them spend winter here, and 28% of the global population breed here. And yet, many of the curlew’s traditional breeding haunts have long since fallen silent.
It’s estimated that 59,000 pairs of the Eurasian Curlew (to us, it’s just ‘curlew’) breed in the UK. Half of those breed in Scotland, and 10% of the Scottish total breed on Orkney alone.
Doubtless that sounds like a lot, but 59,000 represents a 50% decline between 1995 and 2022. The Scottish breeding population has fared worse, declining by 60% in that time.
We’re used to creatures being endangered here in the UK but otherwise listed by IUCN (International Union for Conservation of Nature) as species of ‘least concern’ globally, on account of them doing fine beyond these shores. But for once, the decline isn’t limited to just the UK. Population declines have been seen elsewhere across the curlew’s range – in Scandinavia, the Netherlands, Germany, Estonia, Russia, Belarus.
As a result, IUCN now lists the Eurasian Curlew as ‘Near Threatened’, and in 2015 it was also added to the UK Red List of Birds of Most Concern, meaning it needs urgent action to ensure its long term survival.
For many threatened species, it’s common to immediately point towards climate change as being to blame. Certainly, curlew decline has been found to be more pronounced where warmth and dryness are both on the rise, which isn’t really surprising given that, during periods of drought, soil-dwelling invertebrates descend lower in the ground to where it’s wetter. This potentially puts food out of reach of the curlew’s long beak, or there being less food on the surface for the chicks.
Sea level rise is also likely to put pressure on the coastal habitats the curlew favours.
However, the survival rate of juvenile and adult curlew is considered to be both high and stable, in spite of the backdrop of climate change, so there’s something else going on.
Curlew are long-lived birds, typically living to between 5 and 10 years but they can live as long as 20 years, and the oldest ringed curlew was more than 32 years old! So it’s not that we’re losing adult birds, rather it’s the productivity of nests / chicks that is falling short. There’s just not enough of the new generations of curlew surviving long enough to be successfully recruited into the wider population.
What’s going on?
There’s a wealth of information online about what the possible drivers of this decline in productivity are. You’ll see all sorts: human disturbance, dogs off leads, previously boggy fields being drained, inappropriate developments on or near breeding sites, even trampling or egg-eating by livestock. But there does seem to be general agreement that decline in productivity can, in large part, be put down to just a few key things.
Habitat change or loss is a biggie, such as moving from traditional farming methods and rotation to intensive agricultural practices. Silage production can demand more cuts of a field, which can disrupt curlew breeding if it’s done too early or too often.
Afforestation is another major concern. Historically, the kind of marginal wet grassland that curlews favour has often been the habitat seen as easy pickings for forestry plantation schemes. Especially of densely planted, non-native species.
But even where trees aren’t planted, the modern pressure to reduce grazing levels means some curlew habitat can become too overgrown, or see naturally regenerating tree and shrub encroachment, which curlews don’t like. Conversely, too much grazing can also have a negative impact.
Trees themselves aren’t necessarily bad, it’s more the effect that trees and woodland have on predator presence and behaviour. Tall trees can obstruct a curlew’s clear view of approaching predators, but can also harbour them too. Crows, for example.
Curlews tend to avoid landscapes where trees are present, but even if the curlew’s breeding ground still has a mostly open structure, the mere proximity of woodland can adversely affect the curlew’s breeding chances, because woodland also affords shelter or cover to predators. It’s interesting to read that even woodland as far away as 0.5km to 1km from a nest, can in some situations exert a negative impact on breeding success.
Predation plays a big part in curlew decline, and there’s no getting away from that fact. Meso-(meaning ‘middle’)-predators like foxes and crows (and other corvids) are observed as having the biggest impact, but predation can come from gulls, badgers, pine martens, stoats etc.
It’s no coincidence that curlew tend to have more breeding success on or near land where predator control is undertaken as part of land management practices. An 8-year experimental study in Northumberland, where legal control of foxes, crows, stoats and weasels was undertaken, resulted in a three-fold increase in curlew nesting success.
What to do?
Curlew conservation and recovery efforts are focusing on helping more chicks survive to adulthood. There’s no one solution for this, no quick fix, and because every site is different, it’s not wise to generalise about what the causes of decline in any one location might be.
Management options therefore include a whole suite of interventions and mitigations, each of which can help improve a curlew’s chances of breeding success.
With some landscapes increasingly drying out, it can be beneficial to help some ground to get wetter, or keep water in the landscape for longer. Peatland restoration is a part of this, as is restoring floodplains and installing artificial scrapes (shallow depressions in the landscape that stay wetter than the surrounding land).
Removal of scrub/trees/shelter-belts etc might be warranted if they’re shown to be impacting upon curlew success, and if doing so doesn’t come into conflict with other conservation objectives. But clearly it’s also vital that curlew habitat is identified in the planning process, and that development or forestry planting schemes explicitly take this into account.
On farms, cutting grass later will help curlew, and certainly lots of farmers avoid doing this between April and July. If the cut has to be made regardless, one option is to leave large areas around nests uncut.
Grazing (with cattle), or machine-cutting of densely vegetated areas or rushes, can stop open ground from becoming too overgrown, and helps creates a mosaic of varied sward lengths.
Getting to the more extreme end of the scale, some conservation initiatives are using temporary electric fencing around individual nests, with some success. But the last resorts appear to be lethal control of predators, which can be controversial, and the practice known as ‘headstarting’. The latter is where eggs are taken from nests, under licence, hatched/reared elsewhere, before releasing the juveniles back into the wild. This has been successful down south, but one hopes it won’t be needed in the longer term.
Arresting the curlew’s slide is quite the task, but the bird is fortunate to have a lot of research being done in its name, and some high-profile advocates keeping it in the spotlight.
Writer, TV producer and environmentalist, Mary Colwell, is arguably the curlew’s most energised supporter these days. In 2016 she walked 500 miles from Northern Ireland to Lincolnshire to investigate and highlight the plight of the curlew. Thereafter she founded the charity, Curlew Action, which has championed the bird’s conservation and recovery across these isles and beyond.
In 2017 she also started World Curlew Day, which, appropriately, is coming up on 21st April, Easter Monday. So while you’re chomping on those chocolate eggs this Easter, or taking the kids on an egg hunt, spare a thought for the real thing – those precious speckled eggs out in those fields, recently laid and hidden from sight, and about to become the curlew’s next big hope for long-term survival.