The Hirundines – Swallows, House Martins and Sand Martins – are some of our earliest summer migrants to return from sub-Saharan Africa to breed in the UK. Sand Martins are often amongst the very first with birds appearing from mid-February onwards, followed by Swallows from the end of March, then House Martins from the beginning of April. Unusually House Martins were recorded on the Suffolk coast in the first week of March this year.
These birds are the background to our summers and a reminder that, despite the weather, our annual seasonal cycles are constant and reassuring. But these birds are disappearing from England! House Martins have declined in England by 14% between 1995-2010 (BTO Atlas 2011) and are now a species of conservation concern. Regional variations are striking with a 26% decline in south eastern England. Sand Martins used to nest along Riverside in Cambridge but have long since disappeared. All three species are moving north east into Wales, Scotland and Ireland. Ireland experienced a 23% increase in House Martins between 1998-2010.
Why is this? Most believe these changes are driven by temperature, humidity and therefore food availability. All three species are insect eaters, catching prey on the wing, and our drier summers combined with agricultural insecticides may have reduced food availability. The disappearance of pasture and grasslands from eastern England that support insect communities, maybe another factor. The absence of available wet mud for nest building near favoured communal nesting sites may also affect House Martin distribution.
House Martins collecting wet mud for nest building
House Martins also present another dilemma. They nest under the eaves of houses and other buildings and make a mess! In the 1960s there was a large House Martin colony under the eaves of the old Milton Road infants and junior schools at the junction of Milton and Gilbert Roads (now that’s going back!). The nests were destroyed and the birds never returned.
As delightful as these birds maybe there comes a time when property owners have to paint/repair, and may even remove nests to facilitate building maintenance. This is the issue at the Addenbrooke’s site, Cambridge, on the University buildings opposite Out-Patients. This has one of the largest House Martin nesting colonies in Cambridgeshire with over 100 nests. There are alternative to nest removal. Some nests can be retained, intact, to keep the core of the colony and encourage returning birds to rebuild breed and return again; artificial nests can be installed. Ideally, the work should have been started – and completed – in winter, well before the birds were likely to return. As a species of conservation concern House Martins have protection under the Wildlife and Countryside Act (1981). Members of the Natural History Society, alarmed by the destruction of nests at the Addenbrooke’s site have spoken to staff about their serious concerns who in their turn have undertaken to keep any nest removal to an absolute minimum.
Bob Jarman 11.3.17