Wednesday, 14 March 2018

All Creatures Great and Small, Tawny Owl and Orb Spider - Devon Wildlife

Often heard but rarely seen, the Tawny Owl or Brown Owl is common to Devon and the rest of the UK, but interestingly, not found in Ireland.

This beautiful Owl, Latin name, Strix aluco, is most often heard on an Autumn evening as the light starts to fade and frequents woodland and urban copses, feeding on insects and small mammals.

You can hear the sound of the owl hooting on this link

Tawny Owl

As a young lad I would very often find pellets deposited by these birds, little grey fur sacks of regurgitated skin and bone all neatly wrapped up and left on the ground after the bird had enjoyed a feast of vole or field-mouse.

Taking a razor blade to the pellet would reveal the grizzly remains of the poor creature feasted upon.

These birds are perfected for hunting at night with their eyes so positioned to give a forward arc monocular view of the world below rather than the typical restricted binocular view of most other birds.

That disc shaped face, typical of all owls, is designed to act as a sound director, just like the WWII bomber sound directors, reflecting the slightest sound of a creature scrabbling around on the ground into the ears at each side of the facial disc.

Finally the feathers on owls are very soft and downy designed to minimise the noise of their flight and thus allow them to stealthily attack prey on the ground without any warning sound of their approach.

This particular bird was on the glove of a local enthusiast who rescues injured birds for release back into the wild as well as organising bird handling experiences for interested people and happened to be out on my favourite cycling route flying this hand reared young male bird.

On my way back from my regular cycling expedition I couldn't help noticing a somewhat frantic buzzing sound as I looked for my door key only to eventually find the source coming from a struggling large house-fly or stable-fly snared on the typical sticky capture spiral associated with the web of the British Garden Orb Spider.

The fly in its death struggle as the Garden Orb Spider maintains a firm grip with its fangs

Apparently the family of Orb spiders is the third largest genus of spider in the world with varieties in many countries, some a lot more fearsome than our British varieties, which are only about 2 cms in length and are harmless creatures except to flies.

Only the female builds the classic spider web for catching flying insects and the abdomen seen in the picture shows how this species got such an apt name with its orb shaped body.

When I took this picture the spider had a firm grip on its prey that was putting up a tremendous fight by attempting to break free with frantic buzzing of its wings, gradually becoming less animated as the spider venom took effect to subdue it - nature red in tooth and claw as they say.

Here in my garden in Devon, these spiders are a common site particularly in the autumn when they are mating and laying eggs but also erecting their webs in the most unlikely places such as the gap between wing mirror and car door, finding the space behind a heated wing mirror a great place to set up home.

The appearance in numbers of these creatures in autumn also corresponds to the annual hatching of Crane Flies from the garden lawn which mate and die rapidly but provide a bonanza feast for spiders and birds alike.

I have a strong affection for the Orb Spider as I recollect a presentation, I attended, years ago, talking about the hazards of using certain old drugs in paediatric medicine. During the talk the speaker referred, light heartedly, to the drug experiments carried out by NASA in the 70's in space on the Space-lab to look at various drug effects on concentration, this being a major concern in children of school age.

What better creature to use to model concentration than the Orb Spider and to remind everyone how a concentrating spider builds its classic web, we had a picture to look at.

Then followed a series of pictures illustrating various drugs from LSD, marijuana to caffeine and the effects on web building for these unfortunate spiders, posing the question, what likely effects, if any, on human concentration?

Spider on caffeine to the right
All a bit tongue in cheek stuff with the usual caveats about animal to human modelling, but interesting none the less.

Anyway I really appreciate the Orb Web Spider in helping to keep my kitchen clear of flies and long may they go on concentrating.

I hope you enjoyed this little diversion from military history into natural history. We will be back to the military stuff in the next post.

No comments:

Post a Comment