Rainshadows and other Ephemeralities

Fleeting Glimpses of the Natural World

The other day I found rainshadows in downtown Seattle. I was walking in a light mist along a crowded street lined with trees when I looked down at the sidewalk and noticed the patterns of sweetgum leaves on the concrete. They had been formed by leaf tannins, the same acid that colors creeks and flavors wines, that rain leached onto the pavement. In plants, tannins aid in defense against herbivores and help regulate nutrient cycling and abiotic stress tolerance. These rainshadows, called by some ghost leaves, are a wonderful trace of life, an ephemeral sign of a plant or animal.

The rainshadow of sweetgum leaf in downtown Seattle.

I have long been interested in such evanescent evidence and the clues they provide to life around me. Subtle and short lived, they are yet another joy of being attentive. Here are some of my favorites.

Flight Maps - Fleeting and fluid, the shadows produced by birds flying overhead are always a thrill to encounter. I have seen such flight maps in the city and in the backcountry. I like to think they give me eyes in the back of my head as I am alerted to birds above and/or behind me. When I look around and try and figure out who produced this shadow, I am often rewarded seeing small birds such as juncos and robins, as well as larger ones, including crows, red-tailed hawks, and eagles. But sometimes I am too late and the shadow producer has vanished, leaving behind no trace of his/her existence.

Fin Trails - Recently, I was crossing a bridge over the Pilchuck River on the Centennial Trail with my friend Scott, when he pointed out fish below. I didn’t see them at first but eventually saw their V-shaped ripples headed upstream. Formed by the fish’s dorsal fins, these fin trails allowed me to track the fish into shallower water, where I could see them clearly. Dozens, many at least two feet long, swam below, following their primal urge to return and spawn in their natal stream. State and tribal biologists told me that we were seeing Chinook salmon (they had counted more than a 100 in the river) and that their numbers were going up because of the removal of a dam upstream. A couple of weeks earlier we had seen hundreds of rainbow trout plying the Stillaguamish River, carrying hope for future generations of more fish and more fin trails.

Mob Swoops - My most consistent ephemerality is crows dive bombing a predator. They usually start 10 to 15 feet above their perceived risk, drop down just above the other bird, and slingshot out of attack range. I have seen crows mob swoop red-tailed hawks, bald eagles, and barred owls, all known to find a good meal in a baby crow, as well as the parents. Better known simply as mobbing, this behavior has a long definition basically to the effect of “Even though you are bigger and badder than my gang, we are still going to harass you just so you know that we know about you and your ilk.” Mobbing is often a taught from one generation to the next and between unrelated birds.

I have long liked this image by my friend Tony Angell, from his book “Ravens Crows Magpies and Jays.”

Each of these fleeting signs is a testimony to life and a clue to the complex and intertwined world we inhabit. What further makes them pleasurable and fascinating is that most can be encountered in the urban setting. Please let me know if you see any of these signs yourself and/or have additional types of evanescent evidence to be aware of.

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Writing of crows, two days ago I watched crows dropping horse chestnuts in the street. Similar to what gulls do with clams, crows hope to marry gravity and concrete to crack open the hard nut, and if gravity doesn’t work, there’s always the chance that a car will crush the chestnut and reveal the food within.