Silchester Wildlife Diary: September Highlights

Pipistrelle Bat

September is one of those change or “shoulder” months. At the start of the month it can still be warm and sunny and the Common still looks beautiful with its blaze of pink and purple heather, interspersed with the golden yellow of the gorse. By the end of the month things will look very different as Autumn will be upon us.

September is the month in which many of our summer birds will fly back to their feeding grounds in Southern Africa. The nightjars will already have returned south at the end of August but look out in early September for groups of Swallows, House Martins and Swifts gathering together into groups on telegraph wires or the side of buildings as they prepare for the start of their long migrations back south.

September is also the month in which the bat roosts will break up in preparation for the winter and so I thought I’d concentrate on these creatures for this month’s diary.

Silchester is home to a number of bat species but one of my favourites is the Pipistrelle bats. This is because they often choose to make their home in and around human habitation and so they are a common sight on summer evenings. As twilight descends they can often be seen in amazing acrobatic displays as they leave their roost to start their hunting for the night. I love watching these creatures from the comfort of my living room window!

The little pipistrelles are so small you can fit them into a matchbox – but they can still eat as many as 3,000 insects in one night!

Pipistrelle Bat

During the summer female pipistrelles come together to form maternal roosts. Each female has only one pup but by banding together they provide each other with warmth and security. You can get as many as one hundred bats in such maternal roosts and in September, when the pups have weaned (from their mother’s milk) and eat insects, you can see them emerging with their mothers in big clouds of bats. This is a really special sight to behold and is unique to September. Once we get into October these maternal roosts will all have broken up and the bats will move away to find their individual roosting spots.  

Finally, a fun fact about pipistrelles – it was only discovered in the late 1990s that there are actually two very closely related species of pipistrelle bat – common and soprano. They are distinguished by the different frequency of their echolocation calls (the soprano, not surprisingly, has a slightly higher frequency). So, you need a bat detector (yes, that’s what it’s called) to tell the difference between these two sub species. A third species of pipistrelle, a slightly larger bat called Nathusius’ pipistrelle, is also found in the UK.

Happy bat watching

Stephen