One of the stranger natural mysteries of past decades has been the sudden decline of one of the most numerous, if least glamorous, of our British birds: the ubiquitous house sparrow.

Once everywhere, from city centre to village green, it had suffered one of the biggest avian slump ever recorded, it numbers slashed by almost half, from 24 million in the 1970s to between 12 and 13 million a couple of years ago. And no-one – not even top ornithologists – know why.

There has been many theories advanced: one was that our urban areas were getting cleaner so there was less food lying about in our streets, not something I recognise from the fast-good litter that defaces our towns at the weekends; another suggested that DIY enthusiasts were filling in holes under house eaves where the birds could nest.

I have always thought it was down to the growth in the domestic cat population, which has grown rapidly since “poop scoop” laws have made walking the dog a more demanding and much less pleasant pursuit.

The Royal Society for the Protection of Birds has always shied away from this theory, possible wary of upsetting the vast number of cat owners in their membership.

But now the good news: according the highly respected British Trust for Ornithology, a science based operation, the fall in house sparrow numbers is levelling off, particularly in our gardens. And one of the reasons for that is the ever growing numbers of gardens with bird feeding stations.

On of the more pleasing statistics is that major supermarkets like Tesco have reported booming sales in bird food. The BTO offers advice on how best to feed your wild birds as winter approaches.

One of the most important actions is to keep your feeders and bird tables clean to prevent to spread of disease.