despite the fact that, in terms of their tree structures, wavl trees are special cases of red–black trees, their update operations are different. the tree rotations used in wavl tree update operations may make changes that would not be permitted in a red–black tree, because they would in effect cause the recoloring of large subtrees of the red–black tree rather than making color changes only on a single path in the tree. this allows wavl trees to perform fewer tree rotations per deletion, in the worst case, than red-black trees.