Built by Hampshire and Isle of Wight Wildlife Trust, the purpose-built structure replaces a sand martin bank which has supported the colony for more than two decades but had deteriorated over time. The new bank draws on modern designs and provides a safe and secure home where these iconic migratory birds can nest, lay eggs, and raise their chicks.

Sand martins nest in natural riverbanks, quarries and sandy cliffs. However, habitat loss caused by development, riverbank reinforcement and erosion has made suitable nesting sites increasingly scarce, meaning artificial nesting banks now play an increasingly important role. 

The new moden bank contains nearly 180 nest chambers and is designed to mimic a natural sandy cliff face, reflecting the birds’ natural nesting habitat. A series of small entrance holes on the front of the bank allow the sand martins to fly directly into tunnels angled upwards, which lead to the nest chambers. Each chamber is accessible within the bank via individual wooden doors, allowing Trust staff to easily monitor the colony with minimal disturbance to the birds.

Ben Pickup, Reserves Officer for Lower Test Valley at Hampshire and Isle of Wight Wildlife Trust, said: “The new bank provides sand martins with a safe, stable nesting space to use each year. We have carefully built every tunnel at an angle so that the nests are protected from predators and the weather, while providing the birds with a familiar, natural nesting layout. Here they will be able to carry out their natural behaviours safely - from flying in and out to laying their eggs and raising their chicks.

“With the potential to support nearly 180 pairs, the bank will help secure Testwood Lakes’ colony and boost Hampshire’s sand martin population, giving these amazing little birds the best chance to thrive.”

It was built with the incredible help of the Volunteer Task Force alongside the Friends of Testwood volunteer group. It was supported by Hampshire Ornithological Society (HOS), who funded the majority of the construction costs. 

Sand martins (Riparia riparia) are one of the earliest spring migrants to reach the UK, arriving from Africa in March. They typically begin nesting from April, often raising two broods before leaving in August to return to wintering grounds in the Sahel region of Africa.

Sand martins are sociable birds and will nest together in colonies, digging burrows in steep, sandy cliffs, usually around water. Each pair of birds will create a chamber at the end of the burrow, and here four or five eggs will be laid.

Sand martins are the smallest member of the swallow, measuring around 12cm in length with a wingspan of approximately 28cm. They are brown above and white below, with a distinctive brown band across the breast and a short, forked tail. Agile and fast-flying, they are often seen skimming low over water in search of insects.

In recent years, sand martin numbers have been affected by droughts in their African wintering grounds. UK populations remain broadly stable but HOS reports that numbers in south-east England have declined. In Hampshire, the species is now almost entirely confined to sand and gravel pits, with just 318 active holes recorded.

A HOS survey in 2021 recorded just three active sand martin colonies in the county, including at Blashford Lakes Nature Reserve. The reserve, managed by Hampshire and Isle of Wight Wildlife Trust, also has an artificial sand bank. 

Ben added: “Constructing such a large structure in a remote area of the reserve was no small task. We simply could not have built this without our volunteers. Their effort, commitment and ingenuity have been extraordinary - they transported hundreds of heavy blocks and loads across difficult terrain, created the tunnel moulds by hand, and supported the build from the first row of blocks to the final render. I am also grateful to Hampshire Ornithological Society for their funding.”

Testwood Lake’s bank allows for improved drainage, secure predator protection and easier long-term maintenance. Protective measures include a sand-coloured render that reflects the natural nesting banks used by sand martins, helping the structure blend into the landscape, along with discreet bird-deterrent spikes along the top.

Visitors can view the new sand martin bank from a nearby bird hide, with peak activity anticipated in the next few weeks, when adult birds are expected to pair up and raise chicks in the nest chambers.

The sand martin colony at Testwood Lakes began more than 20 years ago when birds attempted to nest in temporary piles of sand created during the formation of the reserve’s lakes. A wooden nesting bank was installed soon after, followed by one of the first purpose-built artificial sand martin banks in the country. Testwood Lakes provides ideal habitat for sand martins, with open water, sandy substrates and a rich supply of flying insects to support breeding birds and their chicks.

With the new bank in place, the sand martin colony at Testwood Lakes, and Hampshire’s population, is well positioned to flourish for many years to come.