I have two cockatoos one is 5months and the other 4months old. The younger one eates on his own no problems but the older one wont eat unless he is spoon fed. He has this pathetic cry almost constantly as if he's asking to be fed. How can I encourage him to eat on his own? How can I stop him from crying?

He is very dependent and wants the close interaction with you and has found that he needs to cry to get you to feed him . Myself , I would find that great when he still wants to be hand fed , that means he will become a well bonded pet bird . Spoon feed him food like nutra-berries .
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spoon feed him the pellets and he will get the idea .
Parrent birds will actually push young out of the nest when it is time and have been known to attack the young . I am not saying to do that but it can some times take a while . I knew a man that hand fed his Cockatoo for 15 years once a day . and only stopped then the man ( Gary) got sick and was taken away fromthe bird for 2 months .

Raised many birds and have 7 parrots now
Icarus - Fischer Lovebird, Ruby-Fischer Lovebird, Charles Dickens-Quaker Parrot, Linus-Green Cheek Conure, Giggles-Peach face Lovebird, the twins-Fischers Lovebirds

it may be sick.