built a trap near its nest, in scorched earth just prepare some near the world scar, you'd usually need some extermination dinos to clear out the surroundings so they don't mess up your plan when building traps or trapping and knocking them out, then just lure one out and make sure to fly slightly or beyond their breath reach and you have yourself 5 wyvern milk, make sure to have preserving salts ready or just immediately place them in a tamed wyvern's inventory, unfortunately they don't get un-trapped after they wake up so you either need to unload the area to release them or just kill them so new ones spawn, though if you're playing on a server especially crowded ones it doesn't unload and escape

It is gathered by collecting it from the inventory of wild unconscious female Wyvern or dead Alpha Fire Wyvern of either sex.

Lasts 9 hours on scorched earth in a preserving bin with the addition of preserving salt.

In ragnorak milk lasts 1 hour 49 min in dino inventory

This can be stored in a tek trough to extend the timer to 2 days by putting the milk on a storage box on a platform cart

Get like 8 of this stuff and you should be good for one baby wyvern

It can only be tamed from knocking out a female wyvern at least that’s what I heard

If you knock down a female wyvern a second time, it wont give have the milk in the inventory even if you did not get it the first time.

Mil lasts around 26 minutes in the inventory. Or about 1hour and 45 minutes in a dino's inventory.

Apparently alpha wyverns give a lot of this