Starling

as i've mentioned before basilisk males have a pouch on each side for rearing their young; this is a trait universal to dactylopodinae, and a sort of "pseudo-ovovivipary"! a male's pouch is much more reduced until they've bred, after which the skin there will become more elastic and pronounced in time for when the female lays. after laying her egg, it is placed in the male's pouch(es) and during each summer she usually lays 2 eggs with a 1 month interval. the egg has a very delayed hatching time than birds, and only hatches by the time the next spring arrives. as u can see the gaga stays in the pouch for 2-3 months before it starts to grow a bit uncomfy in there and it climbs onto the father's back.

the first year is the quickest phase of a basilisk's growth rate, and they become able to walk on their own regularly at around 5-6 months (prior to that they CAN walk at 3ish, but its more like, pathetic hobbling where they often fall on their face), but at around 1 year the growth slows down substantially. i imagine that they remain covered in the silly down (the colour i think changes from pure white to more brownish after the first year though) up until around 9-10 years where they finally start to grow into their own juvenile plumage and their individual features become more pronounced.

puberty for basilisk usually occurs at a later age on average than humans (in their later teens) and also occurs more "all at once". as in, it tends to coincide with their first fully adult plumage moult (you can imagine how terribly hormonal their first spring season is...). but even then socially i imagine you're only considered a true adult after a few years post your first true "hormonal season", and body size does not completely stop growing until their 20s.