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Through this fall I’ve been talking about what I tried to accomplish in my new Guide to Trees. In essence, I tried to approach tree identification in the same way that modern birders approach bird identification, to create “a tree guide for birdwatchers”. Most guides to tree identification use keys at some level, which are simple and effective, but can be frustrating because the key forces us to answer a particular series of questions, and in the real world we often notice things that are simply not mentioned in the key. We might see trees like the ones in the photo below – clearly two different species – but a key forces us to begin by answering a question such as “Are the leaves opposite or alternate?”.
First, a little history:
A hundred years ago bird identification was accomplished with keys. Ornithologists carried shotguns, and birds could then be examined at very close range (and with no time constraints). The key emphasized clues like the shapes of scales on the legs – and the bird was identified .
Now we use binoculars. We look at the whole bird – color and shape, as well as posture, behavior, voice, habitat, and more – to make an identification. I wanted to create a tree field guide that used this holistic birdwatching-style approach.
Pros and cons:
This modern style of bird identification developed because we usually can’t examine the birds at length and in detail the way early ornithologists could, so a key to birds is simply not practical. Trees are easy to approach and study, and it’s always possible to use a key, but I think the holistic approach is a more satisfying and rewarding method of study.
- It encourages you to look at the whole tree and to find clues wherever they may be, even subtle differences such as branching structure that are difficult or impossible to describe in words.
- The holistic approach allows us to take advantage of “average” differences and probability, which a key (and its “either/or” questions) does not handle well.
- By emphasizing all aspects of appearance, habitat, phenology, etc. it leads to a better understanding of all of the differences and similarities between species.
- Looking at the whole tree you will quickly develop a sense of the overall patterns of variation: which field marks are more reliable, which are affected by environment, which are most useful for you.
- Without even realizing it you will begin to recognize the gestalt of each species, subtle features and combinations of features that distinguish alders, or aspens, or maples, etc. from all other trees (see photo below).
- By simply looking for patterns that match (and humans have very well-developed pattern-recognition abilities) we will notice new things, which will lead to new discoveries.
A key is analogous to a GPS device offering turn-by-turn directions. It gets you to your destination but without giving you a sense of where you are and what might be nearby. The Sibley Guide to Trees is more like a map, and one of my primary goals was to present the big picture and help put the species of trees in context.
Where to start?
Many people enjoy the certainty and the guidance provided by a key, and feel lost when they open a book and are confronted by hundreds of species of trees. It is important to understand that the species in The Sibley Guide to Trees are organized by family, which emphasizes the fundamental similarities within groups. Learning to recognize a maple, an oak, an alder, etc. greatly simplifies the identification process. If you really need a key, there are many excellent regional botanical references in print, which include detailed keys (but beware that many of these guides do not include cultivated species).
Just as in bird identification, it can be helpful to make your own list of “confusing species” that could occur in your local area. With a small investment of time you can page through the Guide to Trees and create a list of trees found in your area that have simple oval leaves (the most common and confusing leaf shape). Once you’ve done that I predict you’ll see that most of those species have other distinctive features, and the list is not so confusing after all. In the end the quickest and surest way to identify a confusing tree is to show it to an expert, and as you gain experience those “stumpers” will become less frequent, and more interesting.