A Tammick egg can't exactly qualify as an egg, as its soft texture and furred surface is reminiscent of skin rather than a shell. It is round and lacks prominent shapes except for a pair of fully developed wings, with which it can fly very short distances, and a tail.
Newborn Tammicks are quite difficult to catch as they're small and can roll or fly away upon sensing another creature's presence. It's speculated that, like with normal eggs, the growing chick is provided with nutrients inside and in a short amount of time the little round ball of feathers grows legs and a head and blooms into a physically proportionate bird.
It's a heated scientific debate whether Tammicks lay eggs or are viviparous because, despite the absence of a head or any limbs, they begin actively breathing upon birth and can't be qualified as eggs but on the other hand the quick metamorphosis they undergo to reach their definite shape resembles the hatching of a bird.
Tammicks are born (or, rather, hatched) small and looking like chicken.
As they mature the stubby neck elongates elegantly, as does their beak, and they grow a tail the size of their body. They are kings of metamorphosis. Save for the tail and comb their feathers are initially a dull grey, but when cut they grow back blue and when plucked, they grow back green.
That is often a cause for maltreatment from their owners, who hurt their Tammicks with the intent of having a more colorful pet. Due to improper plucking the feathers may not grow back and this results in bald spots on the Tammick's body, so it is greatly advised to simply settle with a blue or grey-feathered Tammick instead.