Chances of a world not spawning mandrakes/tallbirds?

[Jack]

So yeah i just went to my third check for mandrakes in all the grass patchs of my world, and not a single mandrake :UFirst i saw the perfect place for a base, near everything i could want. Then I made my base and went exploring...I havent found any mandrakes AND any tallbirds nests, I have the map 100% explored and i'm always checking for mandrakes in all the angles, but i havent found any... pfffI've got 4 walruses camps and lots of spider dens, 2 pig villages and a pig king, I just cant find mandrakes and tallbirdsffffAlso, does anybody now if i get a smallbird to grow into a tallbird, will it make a new nest? or it will just leave you and start wander around? :U

[Kittiko]

I have seen maps with no mandrakes, no pig king and no tallbirds. I asked the very same question about the smallbird growing into a tallbird and making a nest here http://forums.kleientertainment.com/showthread.php?10258-Hatching-smallbirds but no one was able to answer my question. Every attempt I have made to raise a smallbird ended with it dying, save one which grew into a smallish tallbird and that was killed by an angry horde of spiders because the smallish tallbirds attack whatever mob is near them.

[Jack]

Yeah i once hatched 5 tallbirds eggs and only one survived to be a tallbird, but when he grew from a smallish tallbird, i wasnt with him, so i'm not sure where he went DD: