Thanks Littlepaw and mrsD - your collective idea of a cardboard box was great
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!

I have put one in the kitchen - they have fun with it, getting into and over it, having mock fights about who has possession. They also find a piece of crunched-up newspaper good value - they chase it round for ages, sometimes arguing about who owns it
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Apart from that they are both goggle-eyed about my Brush Turkeys, who they see outside every day. I have a colony, complete with a nest-mound and they come round for food hand-outs. They are about twice the size of Blackberry and Waiwaiaa (the attached picture of the alpha male gives an idea).

I will keep them inside for a while yet and then let them explore outside.