
I did a bit of research to try and find out the origins of the link with death and a lot of it seems to be about the fact that owls are nocturnal and associated with the dark and the witching hours. However I did find some interesting information relating to the Vikings who apparently used to use the hoot of an owl to let their enemies know they were coming to do battle. There is also a link to the Aztecs who used to paint their God of death sitting beside an owl.
Image http://www.deviantart.com/art/Perching-Owl-436456316