Why does Holden care about the ducks?

Holden has a strange companionship with people and things that do not seem to be able to take care of themselves. The ducks are just one example in this story, in Chapter 12, Holden asks his taxi driver, Horwitz, "...does somebody come around in a truck or something and take them away, or do they fly away by themselves?"(81, Salinger). Holden is genuinely worried for the safety of these animals, which he feels can not take care of themselves. Unlike so many people he has met, at all the schools he has gone to and places he's been, he worries about the innocent animals and children, not the phonies who constantly surround him. Over the course of the book we find out that his brother, Allie, died at a young age. Holden, being his big brother, had tried to protect Allie because Allie was one of the only people in the world he truly liked. Allie was innocent and did not deserve to die, but still he was taken from his family. Holden may believe that if he nurtured him more, protected him more that perhaps he'd still be here, which is why, anything that can't seem to take care of itself or needs a bit of protection, Holden automatically feels it falls on him to defend, even if it is a duck.