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It seems to have missing branches, crows are starting to gather, and all the leaves have fallen off.

What question is hidden here?

Bonus: What "kind of tree" is this really?

enter image description here (click to view full-sized version)

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The hidden question, to which I don't have a good answer, is:

How much wood would a woodchuck chuck if a woodchuck could chuck wood?

The birds

First, the birds represent letters in the "birds on a wire" font that is popular among geocachers. From left to right, these are:

  O D H U K A M _ C L F I W

(The underscore represents the top branch without a bird. I thought it was a space character, but the words are all run together without spaces.)

The branches and the leaves

The branches and leaves form a cipher. Following the midvein in each leaf from the stem, there are veins to the left and right. Start at the bottom vein on the first leaf and at the trunk of the tree, then move simultaneously: Branch left if a vein is to the left of the midvein; branch right otherwise. If you come to a branch with a bird, write down the letter that corresponds to that bird. Keep your mental leaf marker where it was, but reset the mental tree marker to the trunk. Go through all leaves.

For example, the first three veins are left, right, right. If we go left, right, right in the tree, we come to the left-looking straddling bird that represents H.

Crypto-Dendrology

This kind of tree is called a Huffman-tree. It is a simple scheme for compressing text. Common letters get short paths through the tree, rarely used letters get long paths. (The shortest path usually is assigned to space or the letter E, but in our special case, the letter O gets that spot.)

Note that each node in the tree is either a branch (corresponding to left/right veins or to 0 and 1) or a leaf (corresponding to a letter). Unlike Morse where you must mark the end of a letter with a pause, the nature of the node itself marks the end of a sequence. That is quite economical, but it can also lead to a lot of gibberish when mis-decoding.

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