It’s that time of year again and, on a dead branch of a cherry tree (just outside my kitchen window), sit four dumpy, newly fledged sparrows. With their large yellow gapes and fluffed-up feathers they look as if they’d be more at home in a Disney movie rather than a suburban garden. With quivering wings they beg incessantly to be fed by their smart chestnut-brown father. Watching them and listening to their ‘chirrup-chirrup’ calls transports me away from Dorset and back to the late 1970s and my Nan’s garden in Tottenham, North London.

I would spend nearly every weekend with my Nan who lived on a smart council estate – one of the first created in the country. The estate consisted of small, cottage-style semi-detached houses each sitting on a decent-sized plot and surrounded by neatly trimmed privet and box hedges.

I used to love going there. With its wide roads and cherry tree-covered roundabouts, it had more of an open, country-like feel about it than the crowded dusty Victorian terraces of Edmonton (where I lived with my parents).

One of my fondest memories of the times spent with my Nan was of her ‘feeding the birds’. To this day I can hardly watch that scene in “Mary Poppins” of the old lady in the shadow of St Paul’s with a dry eye.

Nan always seemed to have some stale bread or sponge cake left over to scatter over the lawn. We would then retire to the kitchen and, from the window, I’d watch in amazement as, in a flash, the green sward would disappear under a seething carpet of black and brown feathered bodies. It would be no exaggeration to say that every inch of that lawn would be covered by starlings and house sparrows noisily battling for every last crumb.

All too soon, the avian spectacle would be over and, while the starlings would fly up to the rooftops and telegraph lines, the sparrows would retire to the safety of the large hawthorn bushes that ran down one side of the garden to continue their noisy bickering and squabbles.

I don’t remember seeing any other species in her garden (aside from the odd blackbird and feral pigeon); the only two species that were present were sparrows and starlings but they existed in vast numbers.

In Spring it was a common occurrence to find a blue starling’s egg in the garden usually left in the middle of the lawn as if the bird had been completely taken by surprise! The pavements at this time were often splattered with the pink, naked corpses of newly hatched house sparrow chicks. I often wondered if they’d got accidentally caught up in their parent’s claws as they entered and left the nests. The amount of corpses certainly proved how many young were being hatched on these city streets.

It’s now difficult to imagine just how common these birds were just thirty years ago. On a recent trip to London I didn’t see one ‘cheeky cockney sparrah’ – not even in St James’ Park where I vividly remember buying bird seed from a man and standing on one of the bridges with the seed in my cupped hands and finding myself smothered in a swarm of bold, little birds.

So, what has happened to the population of this once all-too-familiar bird – a bird that has for hundreds (or maybe thousands) of years been so closely bonded to man? We’re even talking about a bird so loved its even been given its own day – World Sparrow Day. As we’ve moved across the globe, the little house sparrow joined us in our travels and conquests. I’ve watched them on bird tables in Melbourne holding their own against the native rosellas and cockatoos and I’ve watched them being fed in Central Park, New York. They are an amazingly hardy and versatile species so just what has gone so catastrophically wrong for them?

It’s a question that has certainly puzzled a lot of the experts and everything has been offered up as an explanation: climate change, competition from ring-necked parakeets, mobile phone masts and sparrowhawk population increase.

I have my own theory to add to the mix.

If one could time travel back to the late 1970s and visit the council estate where my Nan lived, he would be struck by the profusion of colour for, nearly each and every one of the little front gardens grew a profusion of shrubs and flowers.

Most had a number of rose bushes, garishly coloured hybrid tea and floribunda roses probably planted in the 1960s. Lining the path to the front door were often standard roses and clambering over fences and walls were climbing roses.

My grandfather was a keen gardener (as were most of his neighbours) – in fact there were often keenly fought gardening competitions held between the various estates (which he often won) and, to achieve these beautiful displays, many of the householders resorted to chemical assistance. A war was waged against the greenfly/aphid – a battle bravely continued by my Nan when my grandfather died. Out she would go most summer mornings brandishing her spray, squirting it over the precious roses and, once again, all her neighbours did the same. I’d imagine it was no different in the parks most of which had stunning floral displays and rose beds.

Few knew of the dangers of organochlorine pesticides and these were the first group of synthetic insecticides to come into widespread use after the Second World War. They have very stable compounds that persist long after use. These degrade slowly and are fat-soluble which means they can accumulate in plants, animals and humans.

The garden lawn was also a major source of pride in those far off days. A scruffy lawn or front garden would have been a major talking point for the local neighbourhood gossips so, to help attain the much valued green, moss free look, it too was liberally dosed with chemicals to control pests (such as the cranefly (’daddylonglegs’) larvae (leatherjackets) – so loved by starlings and loathed by gardeners – and it often received top-ups of fertiliser to improve the soil quality.

I well remember groups of sparrows enthusiastically dust bathing in the earth surrounding the lawn and creating little bowls in the powdery soil beneath the rose bushes, covering their feathers in earth that must have contained residual pesticides.

I have kept and bred house sparrows in captivity and was stunned by the amount of live-food provided to newly hatched nestlings. In the early days after hatching the young are almost exclusively feed upon insects. One can often see the parent birds clambering through rose bushes searching for them.

So, were these avid city gardeners unknowingly sealing the sparrow’s and starling’s ultimate demise?

I certainly believe they contributed to the decline and after that ‘knock back’ on numbers the survivors simply couldn’t compete with the rate of change our cities went through. When I was growing up there was (even in the centre of town) numerous derelict/vacant sites and these were often overgrown with nettles, ivy and bindweed. One such site was a derelict Victorian school – it’s now a housing estate. Similar fates have befallen most of the other once-disused sites in London as pressures from an increasing population demand that they are developed. A number of allotments (green lungs in a concrete jungle) have gone the same way.

People don’t seem to have the pride or time to work on a garden. So, most of the neatly trimmed privet hedges have been grubbed up and the turf and flower filled front gardens have been lost to a relentless tide of tarmac and crazy paving. The rear gardens have often suffered the same fate leaving no bushes for newly fledged young sparrows to hide or lawns for starlings to probe. The very houses themselves that used to provide nesting places have drastically changed too. The old wooded fascia and soffit boards have now given way to labour saving UPVC. These don’t rot so of course do not provide the coveted nooks and crannies that starlings and sparrows need to nest in. These are cavity nesting species so such change is going to be disastrous.

I don’t believe we’ll see the vast numbers of these species in our cities ever again and a number of people will no doubt be glad of that – seeing them as nothing more than dirty pests and nuisances. However, their swift disappearance should act as a very important wake up call for us all. Something is very wrong in our environment – something that needs to be put right urgently.

There are so many valuable lessons to be learnt from the decline of the humble house sparrow, not least is the importance of gardens, allotments and open spaces in the urban environment. We must stop building on every available site. These open spaces are just as vital to the wellbeing of every community as is the provision of decent housing and our valuable open spaces need to be managed correctly and with respect they cannot be ‘all things for all men’. They can’t all be sports fields, children’s playgrounds and dog exercising areas; wildlife has to have its own designated areas within our cities that are simply the preserve of nature.

Far too often mankind sees itself as being ‘apart’ from or standing outside of the natural world. It isn’t; it’s just another cog in a very big and complex wheel and when we all learn that we will be on the road to righting so many wrongs.