Owls, pellets and resilience

An owl spent the night in one of our barns this week.  I leave one barn open year round in hopes of attracting owls.  None have yet taken up residence but at least one spends the night now and then.   The one I’ve seen in that barn is the great horned owl.

OwlThe great horned is the largest Arkansas owl. It’s bulkier than a red-tailed hawk, with an even greater wingspread,  Having one swoop by you to get out of the barn is electrifying.  That’s happened to me several times and never fails to spike my adrenaline.

If you’re like most people through history you regard owls with fascination and awe–probably because they hunt at night when people can’t see and have a call many consider eerie.  In some cultures, the call fills people with foreboding and apprehension: a death is imminent or some evil is at hand.  In early Indian folklore, Owls represent wisdom and helpfulness, and have powers of prophecy. This theme recurs in Aesop’s fables and in Greek myths and beliefs. By the Middle Ages in Europe, the owl had become the associate of witches and the inhabitant of dark, lonely and profane places.  Nowadays, for most people, the owl has returned to its position as a symbol of wisdom.

Unless you have an owl barn like we do, you’re much more likely to hear a great horned owl than see one. They have a deep, soft, foghorn-like call of three to eight hoots: “Hoo, hoo-oo, hoo hoo.”

The most vocal Arkansas owl is the barred owl, most often found in bottomland forests. Its typical call is a series of eight or nine notes in two groups: “Who cooks for you … who cooks for you all.” Barred owls nest in spring and early summer in tree cavities and abandoned hawk and crow nests, feeding on small mammals, reptiles and birds. It has a large puffy head without ear tufts of the great horned, dark eyes, lengthwise streaks on the breast and crosswise streaks on the throat.

The screech owl is a favorite of many due to its quavering song that Thoreau described as “the dark and tearful side of music … the mutual consolations of suicide lovers … calling Oh-o-o-o-o that I had never been bor-or-or-or-orn!”

About the size of a plump bobwhite, the screech owl is common year-round in Arkansas, residing in open woodlands near creeks, marshes and fields. In Arkansas, destructive plant-eating insects comprise more than 80 percent of a diet that also includes crayfish, minnows, wasp larvae, spiders, frogs, birds and rodents. Screech owls vary in color from reddish to more brown to gray.

The barn owl doesn’t have much of a call (just a rasping note and a clicking sound) , but farmers like the way they rid buildings of mice.  They stockpile large numbers of small rodents, anticipating the hatching of six to 10 white eggs in the Spring. Each nestling eats two to five mice daily during the eight weeks after hatching.

With its white, heart-shaped face, dark eyes and light-colored body, the barn owl is unlikely to be mistaken for other Arkansas owls. It resides year-round in the state but is not nearly as abundant as barred, great horned and screech owls.

I didn’t see the owl in our barn this week, but I found unmistakable evidence of it: a feather and an owl pellet.

Owl pellets are fascinating.  Owls don’t have teeth so they swallow their prey whole. Their stomachs digest all of the prey they can and compact the rest into a pellet.  The pellets has bones, beaks, feathers, hair and claws from whatever they have caught.  Great horned owls feed on skunks, rabbits, birds, rodents and even bats and domestic cats.   After a meal they find a quiet place to rest and digest their meal.  Then they regurgitate the pellet.  I check the barn most mornings in the winter to see if any new owl pellets have arrived.

One winter the barn accumulated a collection of more than 20.  We used them for a nature study program with kids.  You can carefully unpack a pellet and find out what the owl has eaten.  Sometimes you can find the entire skeleton of owl pelleta small animal.  This gets most elementary students really excited.  As a result owl pellets are for sale for science classes.  We’re glad we can collect for free in our barn.

Owl pellets are also used in research.  Their content reflects the types of animals which are most abundant.  One cave in Utah has been the home of owls for 13,000 years.  The content of owl pellets on the floor of the cave tells us how animal life has changed in the region.

Researchers have been able to correlate changes in climate with changes in animal species.  When the climate was hot and dry, animals were smaller and reptiles  more prevalent.  When the climate was wetter, larger mammals predominated. Species adapted to cool climates were the main component of owl pellets around the ice ages.

High levels of diversity of the ecosystem means that different group of species are ready to expand and dominate when climate changes.  This enables the entire system to maintain productivity in the face of almost any disturbance.  The system is resiilent, even though the relative abundance of each species changes.

Since the 1800s when European agriculture arrived in Utah, really dramatic changes in owl pellets have occurred.  A foreign species, cheatgrass, has invaded and displaced native bunchgrass and desert shrub habitats, while increasing fire frequency.   This invasion has caused an observed shift in the composition and structure of the small mammal community, moving it toward small, grass-affiliated species, while larger shrub-affiliated species have declined.

Cheatgrass thrives on disturbance, and much of this region is now affected by this exotic annual grass. Many human activities have facilitated its spread, including livestock grazing, establishment of mining camps and railroads, and an increase in fires.

When cheatgrass was introduced, it increased the diversity of the region.  But now it is decreasing diversity by crowding out other plant species and the animals they feed.  The resilient owl, however, adapts to whatever prey species are present.  Through all the climate changes over the millennia, owls endure.

So owls are great for research and getting kids interested in nature.  But the best thing about them is just seeing them.  A huge mass with big wide eyes swooping down at night is sure to get your attention.

Come to Meadowcreek and you will hear some owls and, if you’re lucky, see some.

 On the seventh day, only the owl and the panther were still awake. Because they did not succumb to sleep, they were given the power to see in the dark.”
– from a Cherokee creation story


For more on diversity and its impact on resilience see Chapter 6 in our free online book available at this link.