For the last year and a half I’ve been lucky enough to live on the edge of a smallish village, and for the last year I’ve taken part in the British Trust for Ornithology (BTO) Garden Birdwatch survey. I pay a small membership fee for the pleasure of noting down the number of birds I see visiting my garden every week. Now I’m not a numbers person, so I don’t really bother to look back over my observations, but thanks to the survey I do get a feeling for the ins and outs of my avian visitors.
We moved into this house in June, and it took a good couple of months for me to notice that we were visited by tree sparrows. At first I was mortified – how could I not have noticed? But it turns out that the sparrows in this village are on a strict rota – house sparrows dominate the garden in summer, tree sparrows in the winter. I have no idea why this should be so, but the same pattern has emerged two years in a row.
Now the winter season is starting, I’m visited by up to thirty tree sparrows every week, with only two or three house sparrows tagging along. Last winter the numbers steadily increased until I could count fifty individual birds, but I reckon the colony was at least sixty strong at its height. By comparison, the largest number of house sparrows was two. In the spring it’s all change, with the tree sparrows disappearing to their breeding sites (I have no idea where) and the house sparrows moving back into theirs.
Late summer it’s a mixed bag – all the adult birds in the neighbourhood stock up at my garden, while the youngsters join in to learn the ropes. For a couple of months house and tree sparrow numbers are about equal, and plentiful. This is also a time of high blackbird and starling numbers. They are especially appreciative of apples and sultanas.
Early autumn and everything disappears. There’s so much natural food around that my bird table offerings are ignored and neglected. This is when the sparrow populations start to shift for the winter. From low numbers of mixed sparrow flocks, over a few weeks the tree sparrow numbers go up while the house sparrows virtually disappear. I’d love to know why.
And now we’re facing winter again. The autumn so far has been pretty cold. Does this mean a bad winter ahead? The blackbirds and starlings are still shunning the garden, but I expect them to turn up soon when the berries start to run out. Cold weather will bring the winter thrushes and maybe chaffinch and bullfinch, but I expect the tree sparrows will outnumber the lot of them until it’s time once again for them to mysteriously vanish.