Yew seeds have very long dormancy when artificially planted.
They are also adapted to passage through digestive systems of animals that eat/transport them.
But could the dormancy be shorter (or the viability higher) if the seed passes through a birds digestive tract first? (An explanation: the seed's outer layers can get worn down that way, signalling that it is ready to start the process leading to germination.)
That would imply that the dormancy could also be artificially shortened by eg. dipping the seeds in acid and then alkaline solutions, which would be great.