youtube chat info - big thx again and again to @СветланаКлюева-н6у 
English translation only from now on – assisted by Gemini
I hope our little "Bonus 2" gets a good feeding.
At 09:48:45, Bonus defecated and is flapping its wings. All the chicks look great.
I hope Bonus 2 adapts soon.
At 10:29, a parent arrived. It is feeding time and three of the chicks are begging.
Bonus 2 is not reacting or begging for food.
However, it seems Bonus 2 did eat during the parent's second regurgitation.
At 10:29:40, the male arrived. It brought fish for feeding. All four chicks ate. At 10:31:29, the male flew away. There were plenty of small fish.
Bonus was in a defensive mode and is hiding from the parent. Its head is tucked under a sibling.
Nevertheless, it has eaten. We could see it at 10:31:00.
The parents accepted the foster chick without any issues.
It will take two or three feedings for everything to return to normal.
At 10:37, our Bonus 2 has a nice, full crop.
Bonus 2 eats quickly and keeps up with the other storklets. Perhaps it was not raised by humans for very long.
Does anyone know what happened to the little stork previously and why it was placed here? There is no information about the extra chick on the forum yet.
It was ringed a bit early. It is still growing. Perhaps the rings will be swapped when the remaining chicks are banded and tagged.
I believe it was ringed at a rehabilitation centre after its original nest was destroyed.
The original nest must have collapsed, and this chick is the only survivor, but this has not been confirmed yet. We have to wait for official information from the Eagle Club (Kotkaklubi).
In a day or two, it will adapt fully and we will see a happy Bonus 2. Everything is new for the chick: the nest, the siblings, the parents, and the noises. It takes time.
At 10:50, the siblings are cuddling.
Give them all some time. It is the first day for the family. Storks cannot count. The only one facing difficulties is the little one, as everything is new to it, and it is old enough to realise the change.
continuation:
? (from 2:18 PM i the chat visible now)
Some viewers worry that its plastic leg ring is disturbing it when it tries to stand up, while others think it is just too young and only starting to walk.
14:07 – Feeding. It was the same as the next feeding at 15:03.
15:03 – The bonus chick did not eat. It only hid among its siblings. (Note: One viewer thinks the chick might be afraid of the new female and prefers only one parent).
15:36 – The bonus chick got up on its feet.
15:36:50 – The chick has problems getting up.
15:39 – The chick is standing for a short time to do a "ps" (poop). This means it has eaten well before.
15:40 – The chick is standing and exercising its wings.
