Birds rate of death never changes. With humans, the older you get, the more likely you are to die. With birds, an equal number of old birds die to the number of younger birds. They just don't die of old age. So Tobias is either living forever or going to be killed by some predator. Also, when did Rachel start to come onto Tobias. Sometimes I think she treats him like her doll or something. She fell for the bullied kid Tobias, not the hunter call of the wild Tobias.