A furry stranger arrived in our garden this evening; he was found clinging upside down to a shrub. We watched as he began to scramble from twig to twig. Now and then, he would flutter a couple of feet, but couldn't quite get into the air.
A quick look at the small ears and nose and some leafing through my wildlife guides, I had him down as a Pippistrelle (Latin for "I squeak" - and I can confirm first-hand that they do). These little guys eat maybe two or three thousand insects in their nightly four-hour hunts, finding their prey with FM sonar - catching a fresh victim as often as every 4 seconds.
The trailing edge of his last wing seemed a little damaged; I took him from our cat-haunted garden, and left him hanging upside-down (the right way up, for a bat) from a tree.