Sunday September 27 2020




Village Nature Diary with Mary Green

Caterpillars and snails

Posted on March 30 2019 at 1:28:25 0 comments


Mary Green reminds us of the important role played by ‘pests’.

Following last month’s article about hedges (and the lovely reader’s letter that echoed it), I have been horrified by some of the roadside hedge cutting done this winter.

I turned off the canal down Grange Lane near Alvechurch which had hedges flailed right down like pieces of Weetabix, and the birdsong went absolutely silent.

Down Scarfield Hill, once a really old varied hedge with woodland flora underneath, it’s been chopped down square to under a metre – only a foot high in some places.

It’s set back from the road with a decent verge, so wasn’t causing any danger to traffic. Then I found the same in Cofton Church Lane, a really quiet dead-end lane.

It must be deliberate. These hedges will be useless for removing diesel particulates or hosting insects and birds and although they will grow back, the shape and structure of the trees will have been ruined.

I wrote last month about wrens, but all common birds have amazing habits and stories. The way they lay and hatch their eggs is fascinating.

For a start, why lay eggs, which are vulnerable in the wild, rather than keep them safe and warm in their bodies like mammals do?

The answer is that birds need to keep the weight low so they can fly, and they have too hot a body temperature for young.

Eggs need shells to protect them, so birds have to eat a lot of calcium. They get much of this from eating snail shells. One of the reasons that some birds are in decline is the lack of snails, killed off by our habits.

Some of our most common birds, great tits and blue tits, have complicated ways of making sure their eggs hatch and chicks grow. They can delay fertilisation for up to a week after mating.

Once the eggs are laid, they can grow or lose feathers on their breasts to warm or cool their eggs and control their hatching.

They are waiting for the hatching of the specific caterpillars their chicks feed on, the winter moth, which feed on fruit trees, whose leaves’ arrival is dependent on the warmth of the spring.

It seems strange: when the weather is cold they don’t warm their eggs so much, but when it’s warm they warm them up.

This is to delay hatching in cold weather, and speed it up when it’s warm and the caterpillars will be there.

Birds vary in how fully developed they are on hatching: blue and great tit chicks are still naked and blind when they hatch. But the parents’ clever timing means they have a good chance of survival.

Some birds are even cleverer than this. Different groups of cuckoos lay different patterned eggs to match those in the nests of the birds whose nests they lay eggs in.

In return, some potential host birds have evolved complicated patterns on their shells to stop cuckoos imitating them.

Cuckoos depend on the tiger moth caterpillar especially, so we lose them where there isn’t their preferred insect food, as well as where the host birds disappear through lack of habitat.

As April comes, think about all this going on in the hedges around you, and hope a cuckoo comes around Bittell as it has in recent years.

The mention of caterpillars and snails is a reminder of some of the wildlife we tend to destroy or at best neglect.

It has been estimated that we are losing insect species at twice the rate of birds and mammals. Yet there are campaigns to save tigers and elephants and red kites, but not for insects.

We all love insects when they are pretty, like the butterflies we see at this time of year. I look out for the first brimstone (pale yellow) – which I saw in February this year! – and orange tips, and see tortoiseshells and peacocks emerging from hibernation.

Even so, some gardeners will destroy caterpillars in their gardens and then try to attract butterflies to pollinate their flowers!

Nobody likes slugs and snails, it appears, and a particularly nasty kind of slug killer is only now being banned in this country.

The same is true of gnats and midges, flies and ants. Look in any garden centre or hardware store and it’s full of products to kill them. Yet people put up bat boxes, having destroyed their food.

There’s a lovely line in the film Nine to Five where a woman reads through her shopping list: “. . .cat food, dog food, ant spray, rat poison.”  That just about sums up our odd attitude to animals.

So, it’s not surprising that the reasons given for declining insect numbers include habitat (which we destroy usually for convenience and profit), pesticides (which we use on purpose), pollution and climate change (which we have done accidentally).

Most people only notice the lack of insects when they see that their windscreens and headlights don’t get covered with squashed flies in the summer.

Or they worry about honey bees, without realising that hundreds of other insect species also pollinate plants. Even I find it hard to love midges in Scotland!

Does it matter, since insects are a nuisance to our lives? It does. They are a crucial part of ecology, providing food for birds and small mammals as well as pollinating flowers without which we wouldn’t have vegetables and fruit.

Each insect, each type of butterfly, has its own preferred plant food, so we need the diversity of our natural habitat, not to pick and choose plants and “weeds”.

One of the problems is that we have tended to see Interlinked nature as a hierarchy.

In medieval times it was called the Great Chain of Being: starting with God and other heavenly bodies, going through humans to the higher animals (mammals and birds) then lower animals like snails and insects, then plants at the bottom.

Christians were supposed to respect the whole chain as being necessary and interdependent, but not to see the elements as equal. Noah only saved animals, not plants.

While we were only capable of killing small numbers of animals and plants, this probably worked on the surface, although even early farming methods and hunting changed habitats and led to loss of species.

Today people still seem to see nature like this. We are aware of the need to conserve wildlife, but we usually mean mammals and birds, not insects and plants.

We know that whole complex habitats are needed for health and sustainability, but we carry on using insecticides and herbicides and flailing hedges.

Really, the order should be reversed. Plants are most important as they make up the basic habitat. Then the small creatures like insects and molluscs, and the plankton and krill in the sea, build up the next layer of existence.

Only if we have them do we have the habitat for birds, red squirrels, red kites and Sumatran tigers. And us.

Intensive agriculture is the prime reason for loss of habitat. Only a small part of the planet has been built on for cities or concreted over as roads, but a lot of it is farmed.

Some methods of farming, like raising cattle and sheep on rough pasture and unsprayed meadows, are fairly sustainable: they don’t deplete the soil and they make good wildlife habitats. Too much intensive stock rearing, though, leads to pollution of air, soil and water.

Arable farming is worse, as it leads to destruction of trees and hedges, herbicides killing “weeds” (i.e. native wild plants) and pesticides killing insects. Half of our farmed land no longer provides the earthworms that thrushes need.

It worries me that people can see the issues with farming meat, but not wheat and soy beans and rice.

I must admit I haven’t given enough attention to insects and will try to learn more about them. In my pictures, some of the bees may be hoverflies!

We can start with the interesting St Mark’s fly which comes out in April – it’s large and black with trailing legs, looking a bit dangerous but quite harmless. It loves untidy flowering hedges and hangs around field gateways.

Or we can look at the lovely anthills by Scarfield Dingle (a field of old pasture, “unimproved”) and hear the green woodpeckers that feed from them.

You can help in your garden by leaving untidy piles of woody and leafy bits, planting lots of native flowering plants and some foreign ones that flower earlier and late in the season, getting rid of mown lawn and, of course, not using “pesticides.”

I wrote the poem in spring last year, in Peck Wood. I hope our lovely early spring continues this year.

Blue is not sad. Blue is the colour of joy
I stand in the middle of the wood
Blue surrounds me, my nose full of scent
My eyes a-dazzle, a-dance, alive
Under the huge oaks, golden green
Rising with life after the long winter
Branches curling, arching, embracing
Curvy, unlike the straight ash and beech
A womanly tree, not the male of legend.
The bluebells grow from its roots, the sky
Grows from its tips, the pale forget-me-nots
Mist over where the blue was lacking.
The deep valley was carved by ages but
People’s work has made this wood, kept it
Like a huge flower in their hands
Cupped and overflowing with blue
For me to stand, and claim my life back from winter.

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