It's not deep. The refrain you mention is a simple child-like fable narrative (I'm not sure if Sachar wrote that himself or if it has an actual folk background but whatever).
If the bark of the trees was as soft as the skies, then the woodpecker wouldn't have to work so hard to get his food (he can easily fly through the sky whereas the bark on the trees is hard). Similarly, the wolf on the ground wishes for that same "soft bark" because then the woodpecker would slip down for him to eat. The theme is ridiculously simple: the desire for an easier life always has a tragic end. The degree to which something is hard to accomplish (like in the novel when the protagonist has to journey through the waste land) makes it worthwhile and productive.
It's not deep. The refrain you mention is a simple child-like fable narrative (I'm not sure if Sachar wrote that himself or if it has an actual folk background but whatever).
If the bark of the trees was as soft as the skies, then the woodpecker wouldn't have to work so hard to get his food (he can easily fly through the sky whereas the bark on the trees is hard). Similarly, the wolf on the ground wishes for that same "soft bark" because then the woodpecker would slip down for him to eat. The theme is ridiculously simple: the desire for an easier life always has a tragic end. The degree to which something is hard to accomplish (like in the novel when the protagonist has to journey through the waste land) makes it worthwhile and productive.