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The Right Way to Roof a House? The Case of the Upper Stanmore Swifts

In Hampshire traditional swift nest sites in our roofs and eaves have vanished in their thousands as houses are demolished or renovated or have uPVC eaves and soffits installed. But in Upper Stanmore, Winchester, due to a serendipitous combination of roof design and roofer oversight, a remarkable Swift colony in just three streets has survived and flourished.

The Stanmore Estate was built as public housing by Winchester City Council, primarily in the inter-war and post-war periods. Building of the Upper Stanmore houses began in 1946. Most houses were of traditional brick-built construction, but as permanent prefabricated housing was seen as a quick way to provide homes, 50 timber Scottwood houses and 50 steel BISF (British Iron and Steel Federation) houses were erected.

The Stanmore Estate in 1952.  Upper Stanmore is on the bottom left.
The Stanmore Estate in 1952. Upper Stanmore is on the bottom left.

When Hampshire Swifts carried out a survey of Winchester in 2018, we were struck by the fact that almost all of Stanmore seemed to be devoid of Swift nest sites. None were found in Lower Stanmore, and in Upper Stanmore Swifts were found nesting in only 30 houses: 11 in Minden Way, 6 in Wolfe Close and 13 in Sheridan Close. Given that nearly all the houses in Stanmore were built prior to the 1960s, it is likely that they would have had gaps or crevices under the eaves or under roof tiles where Swifts could access a place to nest. However, by 2018 hundreds of houses – many still owned by the City Council – had been re-roofed and had uPVC soffits and fascias installed in place of the timber originals. That process has continued as part of the Council’s ongoing maintenance programme of its properties, or as privately-owned houses are sold and renovated. But to my delight and relief when I started surveying Upper Stanmore this summer, Swifts continue to nest there, still it seems in just three streets.

Minden Way houses, all currently with nesting Swifts
Minden Way houses, all currently with nesting Swifts

So, how is it that Swifts have been able to nest in this small area of Upper Stanmore? All the houses where the Swifts nest were originally permanent prefabricated houses, largely Scottwood houses, erected in around 1948. At some point, their walls were covered in plastic cladding. Three of these houses still have roofs and gable-end wall tile panels made of asbestos, but the remainder were re-roofed at least 23 years ago with sheets of Decra, a product that looks like tiles but is made of steel. Some of the nests are accessed via gaps in the asbestos tile panels on gable end walls, but in most cases, Swifts access their nests via the openings at the front edge of the roof.

Asbestos tile panels on a gable end wall.  Several pairs of Swifts access their nests via gaps in these panels
Asbestos tile panels on a gable end wall. Several pairs of Swifts access their nests via gaps in these panels

Close up view of Swift nest entrance in a Decra metal roof, designed to look like tiles
Close up view of Swift nest entrance in a Decra metal roof, designed to look like tiles

The design of the Decra roof with its many ‘channels’ leading up underneath it means that each semi-detached house could potentially host multiple pairs of Swifts, or indeed House Sparrows. The largest number of Swift nests we think we have found in any one of these houses is four, but that may be an underestimate of the true figure. Determining the exact number of nests is challenging because the nest entrances are often very close together and the nest owners enter at great speed. The size of the Swift screaming parties hurtling past these roofs – currently often more than 25 birds – is a thrilling spectacle and evidence of the importance of these Upper Stanmore houses for breeding Swifts.

Despite their evident popularity with Swifts, we have some concerns about how safe these roofs are as nest sites. As a Decra roof is made of metal, the temperature underneath it must often get very hot. With the climate crisis leading to increasingly hot summers, the fledging rate of Swift chicks reared in such circumstances may plummet.

Another concern that Tim Norriss raised was whether the fledging Swift chicks could successfully negotiate the gutter below the nest entrances in these Decra roofs. To answer this question, Tim, Roger Maynard and I visited Upper Stanmore with one of Roger’s ladders. With the kind agreement of Glen, a long-term resident who has had Swifts nesting under his roof for many years, Roger and Tim inspected the nest entrances and the gutter at close quarters. This was reassuring as it was evident that the nest entrances are some distance above the gutter – a fact not apparent when viewed from the ground – so it seems highly likely that Swift chicks can clear it with ease when they take their first flight.

View of Swift nest entrances with the gutter below
View of Swift nest entrances with the gutter below

Apart from the 30 houses in Minden Way, Sheridan Close and Wolfe Close, we have never found Swifts nesting in the other 60 houses in Upper Stanmore with the same Decra roof. When I talked to residents of the two other roads which have houses with Decra roofs – Walpole Road and Addison Close – they were aware of Swifts flying overhead but they told me that they had never seen signs of Swifts nesting there. But one long-term resident told me that there used to be lots of birds nesting under the roofs until the City Council replaced the old asbestos roofs with Decra. Since then, she said, no birds can get in.

When I looked through binoculars at the Decra roof edge of some of the houses in Walpole Road, it was clear that they had been fitted with a bird stop or eaves closure. This piece of roofing equipment is used to block the convex opening below the eaves course of roof tiles to prevent birds and other wildlife entering under the roof. Due probably to an oversight by roofers, no such bird stops were fitted when the houses in Minden Way, Sheridan Close and Wolfe Close were re-roofed. As a result, the Swift colony has survived, for now.

Birds have nested in our homes for centuries. The widespread intolerance to their presence under our roofs is shameful. It not only prevents them nesting, hastening their decline, but also deprives us of a source of joy and wellbeing. Imagine how thrilling the spectacle of the Upper Stanmore Swift colony with its screaming parties would be now if no bird stops had been installed and all 90 roofs originally fitted with Decra sheeting were still available for birds to nest in.

Catharine Gale, Hampshire Swifts

We are grateful to Glen Sumner of Sheridan Close for allowing us to examine his roof at close quarters and to all the Upper Stanmore residents who talked to us about the Swifts and the roofs.

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