This means the spring floods that cleared the river of vegetation no longer happen, making it difficult for the cranes to use the length of the river to roost out of range of most predators.

BBC: Nebraska��s awe-inspiring crane migration

Top of their success list is App Gear, a range of games which use augmented reality to create stunning interactive levels out of real places.

BBC: Furby, aliens and jigsaws: Top toys get techy for Christmas