Quick update. So far, and against all expectations, we've managed to nurse our little lodger to better health. He can spread his wings and move around on the floor suite quickly - although he generally just sits in the shade. He still can't fly, but I think it'll only be a couple of days. Feeding him was obviously a challenge - but we've housed him near the compost heap where there are many little insects he can eat. Regularly, we we give him a little bird bath, which he seems to enjoy and cools him down in this heat. We lock him up in a cat box and leave him outside at night (to protect him from cats) but during the day he's free to waddle about around the compost heap in search of insects (there are less cats during the day). This is the first time I've ever been a replacement parent for a bird! I only hope he'll survive just that little longer until he's big enough to fly by himself.