Initially I thought this currawong was unwell, splayed as it was and panting heavily. However, after a few minutes in the sun it got up and walked away. It returned to the same spot and repeated the behaviour (lying down, wings spread, tail fanned) another 4 times in the next half hour.
Some interesting reading on this sunning behaviour here: http://birdlife.org.au/australian-birdlife/detail/sunny-side-up