On Owls and Pussy Willows

By Boak Wiesner

With little snow on the ground and barely any vegetation out yet, it’s easy to wander about aimlessly, happening upon whatever presents itself. A sound strategy, too, for finding food for predators of our area. Coming across two feathers of an owl (most likely Bubo virginianus, the Great Horned), got me wondering if they had fallen out as the owl swooped down on some exposed rodent, perhaps a meadow vole or a white-footed mouse, which got me thinking about how easy it has been during this winter of little snow for owls to find the rodents that make up the bulk of their diet. Usually, the rodents have a nice blanket of snow to cover them and let them move about unseen by predators – though not from owls with their remarkable hearing.

This made me recall an old cartoon showing a patchwork of farm fields covered with snow that was making up a quilt for a sleeping giant. An apt metaphor for the real thing! When the snow covers the ground, it provides an insulating layer on it, especially if the snow is light and fluffy. Heat “stored” in the earth from the previous summer warms up the surrounding soil, even up to the freezing point of water. While this doesn’t melt the snow into liquid, it does cause some of it next to the ground to evaporate, only to become refrozen somewhat higher up in the snow pack. This is called the depth hoar. An open layer forms in which small animals can move about. What an incredibly good insulator snow is was a point driven home to me a few winters back when my students and I measured a temperature profile for a snow pack that was about two feet thick. At the top: -34°F, at the bottom +32°F: a 66 degree differential! Not much of that happening this winter, though.

So owls eat mice and the mice eat seeds and other parts of plants and the plants – well, what do the plants “eat”? They make themselves, literally, out of the thin air, as they absorb condensed and precipitated water through their roots and carbon dioxide into their leaves. But they also need a smidgen of other elements, too. One of their main needs is for nitrogen to make amino acids and proteins. Most plants need to have nitrogen already “fixed” for them but some plants can do this on their own.

Some of these are the willows. How nice that pussy willows are out already! Their name coined for their appearance, of course, they are the “cat”kins of the willow plant, the male flowers. Several species of trees produce catkins which are quite nutritious, the outside covering of the pollen grains providing both carbohydrates and proteins. As willows grow, die, and get decomposed, the nitrogen compounds in them become a source for other plants. Willows come early in the succession of communities because of this neat trick.

Boak Wiesner is a Minnesota Naturalist volunteer.

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One Response to On Owls and Pussy Willows

  1. JNe Larter says:

    I love the pussy willows. Where can they be found at the arboretum? Jane Larter

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