The birds have little "sub-dural space" between their brains and their skulls, so the brain does not have room to bump around as it does in humans. Also, their brains are longer top-to-bottom than front-to-back, meaning the force against the skull is spread over a larger brain area.
Close examination of the birds' movements permitted researchers to create a computer simulation. It revealed that:
Firstly, the hyoid bone's looping structure around the whole skull was found to act as a "safety belt", especially after the initial impact.
The team also found that the upper and lower halves of the birds' beaks were uneven, and as force was transmitted from the tip of the beak into the bone, this asymmetry lowered the load that made it as far as the brain.
Lastly, plate-like bones with a "spongy" structure at different points in the skull helped distribute the incoming force, thereby protecting the brain.
Link -via Nerdcore | Photo: Flickr user texas_mustang