I don't know that it happens from shipping but, it seems like everyday someone mentions a bird walking backwards, or doing sommersaults, and most often it is a SILKY. Silkies are extremely popular so that may account for the sheer number of reports. I expect people will be labeling it as "silky syndrome" some day soon. It seems to be most prevalent in breeds with vaulted skulls. I recall someone posted actual xrays of a silky skull or link to it and it showed there was just the layer of skin - no boney structure covering the brain. They are very prone to head injuries from bumps or pecking. Not all silkies have this problem. Sometimes it is a cochin or other breed. It is especially sad since they are such a sweet breed.
I have zero experience with silkies so I just throw this out as a general question: Are silkies overbred as a result of their popularity resulting in a genetic predisposition to this type of injury? Kinda like how certain dog breeds end up with hip dysplasia as a result of bad breeding?