What happens when healthy birds shit on unhealthy birds?

May be infected with parasites.

Healthy bird droppings contain some bacteria, enzymes and other substances that are beneficial to the health of birds, but they may also carry harmful viruses, parasites and other microorganisms. Therefore, feeding healthy bird droppings to unhealthy birds may lead to the spread of diseases or parasites through feces, leading to the infection of healthy birds with diseases or parasites, and ultimately affecting the health of birds.

Different kinds of birds have different dietary tastes and habits, and the ingredients in the feces of healthy birds may not be suitable for other birds to digest or absorb, so feeding them to other birds will not have a healthy effect.