Over the last few years, senior ecologist Dr Iain Malzer has been looking at curlew across the RSPB’s reserve network and identifying where we can create top quality habitat for this species. Today he outlines how curlew ecology changes as we approach winter, and how it is important to consider conservation management opportunities throughout the year for vulnerable species like curlew.

Curlew at rest

Temperate breeding bird species, including the curlew, often undergo noticeable and interesting changes throughout the seasons. The breeding period is regularly the main focus of conservation works as the number of offspring produced is so intrinsically linked to trends in the wider population. This means for projects like CurlewLIFE a critical focus is ensuring our curlew’s upland breeding habitats are in top condition, giving the birds the best chance to maximise the number of fledged young entering the winter months. However, as the nights begin to draw in, we also need to think about what our curlew do during their non-breeding phase, in the autumn and winter months, what pressures they face, and how we might maximise their chances of survival.

Generally, British breeding curlew leave their diverse breeding habitats around late July, though birds that have failed can leave earlier. In successful pairs, adult males tend to leave slightly later than the females, as males remain with the chicks until they can fly. The wintering locations can vary widely between different breeding populations. Scottish curlew can often move to the west coasts or Ireland, while more southern birds can move to France and further. Many birds from the continent, from places like Finland, migrate to eastern British shores to spend their winters. They can begin to disperse again around February returning to reoccupy breeding territories in March.

Coastal habitats are the main wintering locations for curlew. They will occupy rocky shores, mudflats, saltmarshes, mussel beds and fields adjacent to coastal areas, some inland wet grasslands can be important too. Prey will vary between these habitats, from marine worms captured by probing into soft, muddy substrates as the tide comes in, to crabs and molluscs in rocky areas and earthworms in more arable fields. The weather and tide cycle can have a significant impact on where birds feed. For example, when the tide is high birds may be forced into adjacent fields to forage, or conversely, when the ground is too hard to probe due to frost, intertidal zones will be vital. Foraging strategies can even vary between sexes and individuals, probably linked to bill length, with shorter billed males often feeding on terrestrial habitats where prey may be closer to the surface.

A curfew of curlew

To survive the winter, curlew must satisfy high energy demands by feeding efficiently. Any limitations in their ability to feed, caused for example by poor weather, can have significant implications for their survival and the overall population. Therefore, it is important we understand the pressures they face at their coastal wintering habitats. Some of these areas are threatened with development or changes in land use. Further pressures come from human disturbance, where birds are scared off of their feeding areas by people. Moving and finding new foraging areas is energetically demanding for birds, and it is important we undertake any recreational activities sensitively.

Some of the best areas to see large gatherings of wintering curlew can be on the Solway, Lough Foyle, Morecombe Bay and the Wash at this time of year though they can be seen on many coastlines. High tide roosts, such as those at Snettisham RSPB Reserve can be especially good. This is when birds concentrate in relatively small areas while they are forced from their intertidal feeding zones. Our latest counts show that, across the RSPB reserve network, key estuary and intertidal sites host around 10,000 wintering curlew annually. We’re making sure the most important reserves are in top condition for curlew. In field foraging areas, they like vegetation to be less than 15cm and so vegetation management is important. We can also keep ground water levels close to the surface to make prey more available. Finally, we are making sure key intertidal and roost sites are protected and free from disturbance.

Dr Iain Malzer – RSPB Senior Ecologist

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