Harrow BioBlitz – part 2

My last post described listening for – and watching the bats at the Harrow Beekeepers’ Association apiary, and setting the small mammal traps on the Friday evening. A group of us re-convened on the Saturday, and first task was to collect and open the mammal traps.

Out of 12 traps, we found a number had been sprung, though in several cases the only inhabitants were slugs (it had rained the evening before). However 3 were more productive, each containing a single short-tailed (or bank) vole. Two adults and a juvenile, these little herbivores are among the most common mammals in Europe. All were unharmed by their overnight adventure and were let go to scamper off into the grass around the apiary.

Short-tailed vole

Taking a close look

Next, we set off – singly and in pairs and threes – to every corner of the apiary, noting anything and everything as we went – trees, shrubs, birds, insects and more. Personally, I was surprised at the wide variety of shrubs and trees on the site. A survey like this, whilst not ignoring anything, barely scratches the surface (especially as none of us were expert plant-hunters/identifiers) yet we found easily more than 40 species on what’s really quite a small patch. Of course there were plenty of insects (although only one of the participants actually noted Apis mellifera – the honey bee!). We did find, however, a nest of Yellow Meadow ants (Lasius flavus). These are significant as they are a species that takes the caterpillars of endangered chalk hill blue butterflies into their nests, affording them protection and helping the butterflies to thrive.  Other interesting finds included galls of the Acorn Gall wasp (Andricus quercuscalicis). These wasps are relative newcomers to the UK, arriving in the 1960s, and reduce the ability of the oaks to reproduce.

Sampling the River PinnAfter a tea-break mid-morning, our bat guide from the previous evening led us in a river-dipping exercise. Some of the HBKA members were surprisingly keen to get the wellies on and poke about in the River Pinn (which runs right through the apiary). Examination of the results indicated the river was surprisingly healthy and had a rich abundance of wildlife. Observations of the river have shown that it periodically gets polluted, but at least on this occasion it was supporting a lot of life. This included lots of freshwater shrimps, cadis flies, water hoglouse, mayfly larvae, leeches and quite a few small stickleback fish.

Checking the river finds

Other finds included a wide variety of slugs, but including the carnivorous Leopard slug (Limax maximus) – a gardener’s friend, this one, as it eats other slugs! Spotted flying over the apiary, along with the expected pigeons, magpies and blackbirds, were a couple of ring-necked parakeets (Psittacula krameri). First recorded in the UK in 1855, these exotic birds (presumably descended from escaped pets) are becoming more common across the south-east and are commonly seen around Harrow.

We wound up the morning around 12:30 as planned. We’d found a rich and seemingly healthy habitat in the apiary, with a few surprises thrown in. In due course we’ll be publishing a full list of species identified, and there’s always scope for follow-up in the form of another bio-blitz or a more detailed and thorough survey. It seems everyone enjoyed the event and hopefully we all learned a little too. Many thanks to all who came and participated, and especially to Rowena for organising loan of traps, bat detector, nets and other paraphernalia, and for her help in identifying and understanding our finds!

Thanks to everyone!
Thanks everyone!

Harrow BioBlitz – part 1

Last Friday, 2nd September, we organised a mini “BioBlitz” at the Harrow Beekeepers’ apiary site, in Hatch End. The apiary is quite a small but diverse site – if you’ve taken the train north from Harrow you may well have seen it, tucked away behind Morrison’s car park. It’s bordered not only by the railway line, but by playing fields, gardens and the River Pinn (which gives Pinner its name). It has small grassy areas, mature trees, river banks, hedges and shrubs.   But we’ve often wondered just exactly what lives there besides the bees.

So a BioBlitz was planned – getting lots of people involved, looking really closely at the full biodiversity of the site, and recording as much nature as they could in just a quick snapshot. We decided that in order to get a picture of the mammals on site, we’d need to be sneaky and set some traps overnight. So on Friday evening a small group of us convened to lay a dozen small mammal traps – very kindly loaned for the weekend by the Field Studies Council. One of their field studies tutors, our very own Rowena, came along and explained in detail what sort of creatures we might find and how the traps worked. They’re humane traps that leave the animals unharmed to be released the next day – seems at the FSC some animals get “trap happy” – they offer free food and dry bedding! Then everyone placed a trap in spot they thought might be popular with our furry friends.

But that was just part one of the evening. Rowena went on to give us a really interesting introduction to bats…  we know there are bats around, people have caught glimpses of them recently. We learned that around 1 in every 4 mammals on earth is a bat – quite amazing for these creatures of the night that we barely interact with. We learned about bats’ echo-locating senses, and about the bat detector devices that allow us to hear the bats’ squeaks even though they’re above our hearing range. (Rowena also demonstrated a range of high pitch sounds to put our ears to the test). Then, with the detector on, we very quickly picked up their sounds. Heading just outside the apiary, we could hear their calls as they navigated, found and homed in on their flying insect prey. We could see, in the very last of the daylight, a couple of bats flying around very low over us, and by the frequency of their calls learned that they were “Soprano” Pipistrellus pygmaeus (so-called because their call frequency is somewhat higher than the slightly more common Pipistrellus pipistrellus). The pipistrelles are Britain’s smallest bat.

As the last of the light faded, the rain came down – but we’d set our traps, seen our bats and it was time to go anyway.

Huge thanks to Rowena and the Field Studies Council for loan of equipment. It was obviously much enjoyed because one of the BioBlitzers purchased their own bat detector that very night…!

Preparing the mammal traps

Rowena explains to the group how the traps are baited and triggered, and what types of animal we might catch in them

More to come, including what we found in the traps next day, in the next post!