Jenny Tweedie, from RSPB Scotland, brings you this blog on how house sparrows are fairing in Scotland and a helpful guide on telling the different types of sparrow apart in time for this year's Big Garden Birdwatch!

Cheerful chirps and boisterous behaviour

With their cheerful chirps, and boisterous birdfeeder behaviour, house sparrows remain one of our commonest and best loved garden birds. Year after year, they rank highly in the Big Garden Birdwatch, taking the number one spot in all but the most rural of regions. And for those of us with feeders in the garden, it would be unusual not to see the local troupe at least once a day.

But for some time now, it’s been clear that all is not well with our sparrows. Although still numerous, their overall numbers have fallen sharply in recent years, with a shocking 90% decline in some urban areas. And what’s worrying is that we still don’t know exactly why.

It’s probably a combination of factors. Gardens have changed dramatically in recent times, with more patios and decking meaning a decline in the types of plants that might support sparrows by encouraging insects in the warmer months, and providing seeds in the colder ones. Fewer chunky hedges reduce available nesting sites, and with less cover around, sparrows, with their short, stubby wings, may simply have become more vulnerable to predators.

We’re still seeing them at our feeders because any remaining sparrows in an area will naturally drift towards the offer of free food, and people who feed the birds may be more likely to have a wildlife friendly garden anyway, offering lots of things that the sparrows need to survive, like good nesting sites and shelter.

But while house sparrow numbers continue to slip (though the decline may now have slowed in some areas), a rather odd thing showed up on last year’s Big Garden Birdwatch results in Scotland. Tree sparrows, a much rarer species usually associated with farmland, came in as the 16th most common bird seen. This was a jump of four places up the rankings in only a year, overtaking birds like the greenfinch and the jackdaw.

So what’s going on?

Just like house sparrows, tree sparrows recently suffered a terrible decline in numbers, with an estimated population drop of 93% between 1970 and 2008. The population is thought to be now slowly increasing, but why are they suddenly showing up in gardens? Have they figured out that bird feeders can help them survive through the worst winter weather when other food supplies are short? Are they adapting to a more urban lifestyle, or simply finding themselves more and more in our back gardens as towns and villages expand?

It’s going to take a bit more research to figure it all out. But in the meantime, this is just one of the many, many mysteries of the bird world that the Big Garden Birdwatch can help us start to unravel.

We really want to know how many sparrows (and other birds!) you have in your garden, so please do register to take part in the Birdwatch on the weekend of January 30 and 31.

And if you’re unsure whether you’re looking at a house sparrow, a tree sparrow, or indeed a hedge sparrow, here’s a quick guide to help you out.  

House sparrow:

Immature males and females can be hard to tell apart, but adult males have distinctive markings. These are still the most common sparrows in Scotland.

Tree sparrow:

With adults, the most notable feature is the cheek spot, but they’re also more chestnut-coloured than house sparrows and slightly smaller. Females look pretty much identical to males.

Hedge sparrow, commonly called a dunnock, or sometimes a hedge accentor:

Much greyer birds, with less distinct markings. You’re more likely to see dunnocks on the ground rather than on a feeder. Again, females and males are very similar.