Life in the silver birch trees

Silver birch trees

Silver birch trees

I love silver birch trees – the white peeling parchment bark, and the long flowing branches thick with catkins are like trusses of beaded hair waving in the wind. Edith Nesbit described them in her poem ‘Child’s Song In Spring‘ as: ‘The silver birch is a dainty lady, She wears a satin gown;’ Poetic indeed. They are the iconic tree of Russia, where the sap is revered as a wholesome elixir that can be taken as a spring tonic and the twigs are used as veniks in Russian banyas. Known as the tree of Venus, the silver birch symbolises love and fertility and in English folklore is said to ward off evil spirits. They are also amazing habitats for invertebrates.

Birch catkin bug, Birch shield bug and Red-legged shield bug

Birch catkin bug, Birch shield bug and Red-legged shield bug

There are four silver birch trees in Warwick Gardens, standing majestically near the railway line and flanked by a hornbeam and a red horse chestnut tree. The distinctive white bark punctuated with lichen clad fissures provide an assault course for insects, complete with nooks and crannies to hide in. Ants run up and down the trunks looking for aphids, deftly sidestepping the red velvet mites, and ladybirds trundle over the bark on the long climb up to a branch junction. There are two bugs that feed on, and lend their name to, the birch tree – the Birch shield bug and the Birch catkin bug. Both are common in Warwick Gardens and can be found chilling out on the catkins or posing on a leaf. Other shield bugs which enjoy living in these trees are Parent bugs and Red-legged shield bugs.

Running crab spider

Lichen running-spider

Evidence of spiders are visible with scanty webs draped across holes in the trunk. Last year something caught my eye when I was walking past a tree – a very camouflaged spider. I just managed to take a photo before it scooted away rather quickly. I uploaded it to Flickr and within minutes had offers of identification by excited arachnologists – a Lichen running-spider Philodromus margaritatus. Now this is a rare sighting of one of these spiders – the last sighting was in the south of England. It feeds on lichen, hence the name, especially that which grows on silver birch trees. The habitat is perfect – our trees are swathed in lichen. As a migrant from Europe chances are it was swept into Peckham by a passing train. I was asked to catch a live specimen to send to the British Arachnological Society for formal identification. Unfortunately daily excursions to the park and several night-time trips clad in dark clothes and a head torch armed with a pot, I was unable to find it. So I still don’t know if we have a rare spider in the park – but I like to think it is living somewhere in the trees.

Oncopsis flavicollis nymph and adult

Oncopsis flavicollis nymph and adult

The Buff-tip moth (though yet to be seen in Warwick Gardens) is a classic example of an insect using camouflage to blend into its environment as it looks identical to a twig of the silver birch tree. The leafhopper Oncopsis flavicollis can be found amongst the leaves and another invertebrate using this tree is the Nettle weevil. So next time you pass a silver birch tree it is worth taking a few moments to look closely at it. You never know what you will find.

Yummy mummy

Warwick Gardens is the perfect place for children – it has a safe playground, a dog free zone, and the log seating nestling amongst the long grass makes playtime for small kids seem like a day out in a meadow. A chance for mums to let them run around. Though sometimes I wish they would exercise constraint over their little ones when they run roughshod over the flowers and scattering the grasshoppers! On the other side of the park hanging tightly onto a leaf high up in the silver birch tree, and keeping her young nymphs close to her, is the ultimate mummy – the Parent bug.

Adult Parent bug, and sitting on her newly hatched nymphs

Adult Parent bug, and sitting on her newly hatched nymphs

Of the ten species of shield bug living in the park the Parent bug has to be one of my favourites. Looking very similar to the Birch shield bug, and sharing the same habitat, the Parent bug can be easily identified on the basis she sits on her eggs. This is very unusual in the bug world. They are reasonably easy to find… it just takes a keen eye and a thorough search through the leaves of the Silver birch tree. These trees have long flowing branches and in high winds wave around quite fiercely. Our bug lays her eggs in a tight cluster on the underside of a birch leaf and hangs on, bearing the brunt of the English weather. She then broods her clutch, sitting protectively over the eggs until they hatch.

Brooding her 2nd and 3rd instar nymphs, and 4th and 5th instar nymphs

Brooding her 2nd and 3rd instar nymphs, and 4th and 5th instar nymphs

Like all good mums the female Parent bug looks after her family until the young finally become adults. As with all bugs, shield bugs undergo an ‘incomplete metamorphosis’ which means they do not possess larval and pupal stages. The adults develop from several stages (instars) of nymphs (up to five) through successive moultings. Nymphs resemble the adults except for size and the absence of wings and they usually have different colouration or patterns. They feed on the sap of leaves.

Update 2nd October

Parent bug nymphs and adults, and a moult

Parent bug nymphs and adults, nymphs on the move and a moult

One month on and I have been watching 6 families of Parent bugs. They are living on separate parts of a silver birch tree branch. I have been fascinated with how they live: bunched together as nymphs as if scared to go out into the wide world, though a few have ventured off and spend their day alone on a leaf. One family insists on walking up a branch to visit a catkin, and later in the day I find them back on the leaf they started from. I have witnessed the moult into adulthood, the lone parent standing by the final nymph, adults waiting for their kin to moult, even a whole family finally becoming adults but still insisting staying together … but today I went to look and all my families had dispersed. I wish them love and luck – it has been a joy.