TEN YEARS ago, one of the most important yardsticks to the health of the British countryside came into being: the annual Breeding Bird Survey (BBS) conducted by some 2,000 amateur ornithologists whose findings are collated by some of the best-informed scientists and conservationists in the land.
For those who consider bird-watchers akin to train-spotting anoraks – cynics know them by the derogatory name of "twitchers" because of the way they rush around the countryside when rare species are spotted – think again.
The rise and fall in bird populations can sound alarm bells not just for the sake of wildlife but for humans too. Back in the 1960s, when birds of prey seemed on the verge of dying out because they were laying sterile eggs, it was discovered they were being poisoned by concentrations of pesticides that had built up in the song birds they preyed upon.
Those pesticides had been sprayed by unwitting farmers onto their cereal crops. Had they found their way into the human food chain, who knows what effect they may have had on human reproduction? As it was, dying hawks set the alarm bells ringing, just as dead canaries warned of methane gas in 19th Century coal mines.
That, I admit was an extreme case and, thankfully, there has been nothing so severe since, but there have been other warnings from the bird populations which show us that something serious is amiss in the rural environment.
For many years, a handful of ornithologists did their best to keep a track of the ups and downs of bird numbers but it was not until 1994 that the British Trust for Ornithology had the idea of getting amateurs involved and set up the BBS with the Royal Society for the Protection of Birds and Government-funded Joint Nature Conservation Committee.
Some 2,000 people volunteered and each was given a square kilometre of countryside to visit three times a year to survey the bird population. The results have been intriguing, some good, some bad, some completely mysterious.
Since the surveys began, 26 species have declined significantly, some for reasons not yet fully understood. Some of those in decline, like the sky lark (down 14%) and the grey partridge (down 39%) are ground nesters and their slump was blamed on intensive farming.
However, some experts believe that it is more connected with a growth in predatory species of both mammals – foxes, rats and escaped mink – and birds like magpies for which ground nests are easy targets.
At the same time, 44 species have grown in number and that may well be connected with global warming, which has made harsh winters virtually a thing of the past. I find it almost impossible to believe that, according to the latest survey figures, Jenny wren is the most common bird in the country.
With their tiny bodies, wrens were always at risk in long, harsh colds spells because they didn't have the body fats to see them through when food was scarce. One of my favourite birds – strange, for an angler I suppose – the heron has prospered, too, because in hard winters, when streams and pools were frozen over for long periods, it could not fish.
So, it would appear, global warming can be good for you – if you are a bird, that is. Combined with changes in farming practice, of which many more are on the way, almost twice as many birds species have prospered compared to those that have gone into decline. So, at last, the no gloom and doom nature story …
Pictures courtesy of the Hamlyn Guide 'Birds of Britain and Europe'