Webcam screenshot from Liz, LK forum
The smaller can no longer stand up.
Black Stork Ciconia nigra
It all started last night, when the youngest hatchling, who probably hatched later, could not want to get up as his/her siblings. A certain sluggishness in behavior could be noticed a little earlier, but it could also be blamed on the heat.
It's sad to see the torment of a bird, but unfortunately things happen so in wild nature and we can't interfere.