Stewart,I have collected many samples from the feeder tray in my garden and would describe them as multi-coloured when absolutely fresh (reflects what has been eaten, ripe blackberries at present) but they shrink and darken within a few hours.When fresh, they tend to be deposited in clusters or sections, often blunt at either end. Much softer than wood mouse droppings and not so dense; coarser material suspended in jelly..... No smell unless they have fed on apple (cidery) or conifer buds, seeds (pine). And yes, juvenile faeces are much smaller than adults.They dissolve quickly in rain whereas mouse droppings go pale but tend to keep their shape.See attached picture.The ones found in nest tubes are usually outside the actual nest but we've found quite large deposits on top of nests in boxes. By the time we find these, they are dark in colour and dry.Jen B