What is the theme of "The Scarlet Ibis"?

The main theme of "The Scarlet Ibis" is that of pride.

The brother of Doodle, who is also the narrator, observes in the early part of the story that

...pride is a wonderful, terrible thing, a seed that bears two vines, life and death.

Pride drives the brother to mold Doodle into normalcy as much as he can, by encouraging Doodle to walk and to become a companion to him, to be able to row a boat and to swim with him. This desire for Doodle to participate in boyhood is the "vine of life." But, in so doing, the brother also acts out of selfish pride because he does not wish for Doodle to be an embarrassment to him. Moreover, the brother desires that Doodle believe, as he does, in his own infallibility. This prideful belief in his infallibility is the vine of death because he coerces Doodle into trying to row and to swim beyond his capabilities.

We decided to double our efforts, to make that last drive and reach our pot of gold. I made him swim until he turned blue and row until he couldn't lift an oar....
We had wandered too far into a net of expectations and had left no crumbs behind.

Indeed, there are no crumbs to follow back to a safe time for Doodle, and "the vine of death" of the brother's selfish pride overtakes this delicate boy, so like the exquisite and fine scarlet ibis hurled into a world that is not his own. Certainly, then, pride is thematic in James Hurst's narrative, "a wonderful, terrible thing."