大象传媒

Ravens are not the only birds that you can find in the Tower of London. Bill Oddie goes to see a house sparrow colony. Sparrows aren't doing that well at the moment - numbers have crashed - but the reason is not known. One theory is unleaded petrol, but Bill isn't convinced. There are about a dozen pairs of sparrows here. They are using a nesting hole in the wall. Sparrows are rare here, but not worldwide. Bill hopes that the UK sparrow population will increase as mysteriously as it decreased.