One month ago three owlets fledged from a brood of four, leaving the youngest in the nest box. It had a dislocated leg but no other apparent injury and couldn't climb out. Possibly it got caught in a tug-of-war with brood mates, as youngest siblings sometimes do. An animal rehabilitator said there was a fifty-fifty chance the leg could be mended, but I left the situation alone to learn more about wild ways. My observational approach to learning from natural history is neutral as much as possible, although my presence, let alone hands-on checking, certainly is not. I may affect a situation inadvertently but try not to take sides.
Through mid-May the male parent roosted in his customary position near the nest box and continued to feed the crippled nestling, while his mate stayed with the fledglings farther away (males typically attend remaining nestlings, and females accompany fledglings). By late May, Dad was no longer present in the daytime, as the rest of his dependents ranged ever farther afield; but the nestling was still fed, for its weight remained steady. Then, a week ago, the owlet began to decline. It died of starvation today, and I learned that triage is no snap decision but is sometimes necessary, as support of the living demands all one's time and energy.
The reason is simple according to the play's directors -- that environmental group called natural selection. Surviving offspring carry parental genes, which permit their parents' acting ability in concert with the plot. For the screech owls' part to continue, some youngsters must survive to become parents, which requires parental care that includes making choices. If roles aren't perpetuated by offspring, who may also exercise unique (genetic) abilities when stage settings change, other actors fill in and the scene shifts, or those roles and the scene disappear entirely.