Sparrows are often considered familiar to the point of invisibility, but the recent steep decline in numbers of both native British species is a reminder that these unassuming chatterboxes deserve a little more attention. Of all the true sparrow species found worldwide, only two occur in the British Isles. Globally, the story of the House Sparrow is one of dramatic expansion: from humble origins in the Middle East where they spread, along with agriculture, to become the most widely distributed bird on the planet. The smaller, more active Tree Sparrow has also spread extensively,...