Nature Notes

The Curlew

The Eurasian Curlew (Numenius arquata) is an iconic bird of this area (eg, see the Wharfedale Naturalists logo). They can be seen in the fields along the Wharfe valley, and small numbers seem to breed on Ilkley Moor (I’m not sure how successfully). The brown plumage of this large wader is delicately marked but not spectacular (see photograph). However, they do have two attention-grabbing characteristics. The first is a long, curved bill. This can be up to 15cm long in females (generally somewhat shorter in males) and it enables them to probe the ground for invertebrates. The second is an evocative call – “curlee”. On a cold, grey, windswept day this plaintive sound can have an eerie quality as it drifts across open ground.

The UK is an important location for curlew, having the third largest worldwide breeding population (19-27%) (Russia and Finland have more) and an estimated 150,000 over-wintering birds. However, in line with global trends, numbers of breeding birds have declined alarmingly in recent years. Consequently, the curlew has been listed as Near Threatened globally, and included on the UK Birds of Conservation Concern red list. Indeed, some have argued that it is the UK’s highest conservation priority bird species.

Low reproductive success is thought to be the problem, and possible causes have been identified. Suitable habitat has been lost. Some agricultural areas now provide grass cover that is too uniform. Curlew prefer mixed vegetation with clumps of longer grasses or rushes. Trampling of nests by livestock can also be a factor. Commercial forestry has reduced habitat, and woodlands bring ‘edge effects’ – providing refuge for predators from which to hunt neighbouring open areas.

Indeed, predation of eggs and chicks may be one of the key determinants of Curlew decline. A study of the effects of predator control on moorland reported substantially increased breeding success for Curlew and other bird species. On Ilkley Moor, over the summer, crows seemed to be taking a sustained and unwelcome interest in an area where I think Curlew and Lapwing were nesting. Management of moors for grouse shooting may be associated with a number of problems (see Nature Notes, 3/1/2019, for a discussion), but can be beneficial in this regard.

It is interesting to consider what can be done to support breeding Curlew on Ilkley Moor. I certainly wouldn’t be one to advocate the reintroduction of lethal predator control – so how can more ‘Curlew-friendly’ environmental conditions be created?