Hubbard Fellowship Post – Mother Owl

This post was written by Evan Barrientos, one of our Hubbard Fellows.  Evan is a talented writer and photographer and I encourage you to check out his personal blog.

Warning: This post contains images of fluffy, baby animals.

Along the edge of one of our prairies there is a road lined with mature cottonwood trees. Although I appreciate the wide-open prairie environment, I like to take a walk once a week in the shady security of this miniature forest. The rustling leaves are soothing, shade is a novelty, and the trees bring back memories of hiking in New York’s forests. I also happen to see a lot of interesting wildlife behavior when I go here. One morning in July I was jogging down this road when I spotted an Eastern Screech-Owl being mobbed by Baltimore Orioles and American Robins. I sprinted back to my house, grabbed my video equipment, and hurried back before the action was over.

For several minutes I filmed as the orioles and robins viciously pelted the seemingly harmless owl (click here for a previous post I wrote about this behavior). It amazed me that the owl could withstand such harassment so patiently. Despite several painful-looking beak-jabs to the back of the head, the brave little owl outlasted the assault and was finally left in peace. Only then did I realize why she had refused to leave; she had babies to look after!

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In a nearby branch I finally noticed three owl fledglings trying to sleep. In addition, there was a second adult screech-owl who seemed equally intent upon sleeping unnoticed. I don’t know which adult was which gender, but I like to imagine that it was the mother who bravely endured blows from the angry songbirds in order to let her family sleep in peace while the lazy dad took a nap. Either way, I always find it touching when I see animals put such great effort into protecting their young.

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On another subject, all three birds in this post are species that used to be much less common in Nebraska. Before Europeans arrived, trees were hard to come by in central Nebraska. Over the last century, however, trees from the East have spread into the state as people have planted them around their crops for windbreaks and around their homes for shade. With trees leading the way, many forest species from the East, such as Eastern Screech-Owls, have ventured into Nebraska and the Great Plains. The ecological effects of this tree march are more complex than I’ll go into here, but overall they’re detrimental to grassland plant and wildlife populations. Here are just a few examples:

  1. Trees provide perches for aerial predators (such as owls and hawks), which increases predation rates of prairie grouse and mammals.
  2. Tree corridors provide safehavens for woodland nest predators (such as skunks and opossums) as well as brood parasites (i.e. Brown-headed Cowbirds), who venture into the prairies for prey/hosts. Thus, wildlife in small prairies bordered by trees experience abnormally high rates of nest depredation and parasitism.
  3. If uncontrolled, trees form dense canopies that shade out prairie plants, which are adapted to full sun. This makes it harder for prairie fauna that rely on prairie plants for food and shelter to survive. The result is a positive feedback loop: the presence of trees encourages more trees to grow.
Doom on the horizon? The trees bordering this prairie are the same ones that love walking through.

Trouble on the horizon? The trees bordering this prairie are the same ones that I love walking through.

So what’s the takeaway? Our relationship to nature is complicated. Nothing is simply good or evil. On one hand, trees may seem like a existential threat to prairies, but on the other, I value them for their soothing shelter and the species they harbor. I think the key to this dilemma is diversity. Although I appreciate woodlands, I also appreciate prairies. But healthy prairies are so much more scarce in eastern Nebraska than wooded roadsides, and grassland species are generally in decline, while most woodland species are stable or even increasing.* Therefore, I would choose to cut down trees that are encroaching upon prairies. This does not mean that I think all trees in Nebraska are evil and must be destroyed, just that we need to keep them in check in order to maintain a balance between the two habitats.

*To make things even more complicated, while tree invasion is a real problem, cottonwoods are actually failing to reproduce in Nebraska. To germinate, cottonwoods need floods to scour vegetation and deposit sediment. Now that Nebraska’s rivers are regulated by dams, these floods happen much less often. As a result, we’re seeing very few young cottonwoods taking their parents’ place.

A Day in the Bluffs

We spent a long day at our Rulo Bluffs property last week.  The site is at the very southeast corner of Nebraska, and includes about 450 acres of mostly oak/hickory woodland with prairie and savanna habitat on steep ridge tops.  I’ve written before about our work to burn and thin the woodlands to open up the understory layer as a way to encourage higher plant diversity and better wildlife habitat.  Last week, Nelson, our land manager, spent the entire day in a rubber-tracked skidsteer, shredding brush along ridges because we didn’t manage to get a fire  done last fall or this spring.  I got a few overhead photos of his work with our drone.

Nelso Winkel shredding brush with a skidsteer at The Nature Conservancy's Rulo Bluffs Preserve, Nebraska.  Using fire, thinning, and shredding, we are trying to allow more light to hit the ground in the woodland, which enhances oak tree regeneration, increases plant diversity, and improves habitat quality for many wildlife species.

Nelso Winkel shredding brush with a skidsteer at The Nature Conservancy’s Rulo Bluffs Preserve, Nebraska. Using fire, thinning, and shredding, we are trying to allow more light to hit the ground in the woodland, which enhances oak tree regeneration, increases plant diversity, and improves habitat quality for many wildlife species.

This photo shows a ridge where we've been working for more at least 15 years to beat back brush with fire and mechanical treatments.  Nelson didn't have to shred this area this year because the brush is finally starting to give way to more herbaceous plants.

This photo shows a ridge where we’ve been working for more at least 15 years to beat back brush with fire and mechanical treatments. Nelson didn’t have to shred this area this year because the brush is finally starting to give way to more herbaceous plants.

The second image above, taken with our drone, was interesting because it and others from the day showed a surprising number of large dead trees scattered across the property.  We knew we were reducing the number of smaller diameter trees with our thinning and fire work, and that a few bigger trees were also dying, but couldn’t see the real scope of that without being in the air.  (Couldn’t see the forest for the trees…)  While we’re not trying to kill off a large number of big trees, losing some provides space for new oak trees to get started, and provides a number of other benefits – including habitat for the many species that live in standing dead timber.  So, it wasn’t a shock or disappointment to see all the dead trees, it was just an interesting observation we couldn’t have gotten without the ability to get eyes up in the air.

My main job last week was to be on site in case Nelson ran into trouble with the skidsteer.  (That makes it sound like I was there to help fix the skidsteer – nothing could be further from the truth.  Nelson has more mechanical ability in his little finger than I could dream of.  I was just there to go for help in case he rolled the thing down the hill or something.)  While he was doing the real work, I tried to stay productive by pulling garlic mustard, scouting for invasive honeysuckle, and killing small trees with herbicide.  I also managed to find a little time for some photography.  Here are a few of the photos I took.

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This is starting to look more like what we want the site to be.  A strong herbaceous (non-woody) plant community, including sedges, grasses, and wildflowers, supports better wildlife diversity and also helps facilitate fire to maintain that open woodland character.

 

These paw paw trees were top-killed in our 2014 prescribed fire. they are regrowing from the base, but aren’t yet tall enough to suppress growth of other plants beneath them.

 

A small bur oak is fighting to establish itself on a prairie ridge as older oaks near the end of their lives.  Both in the woodland and savanna portions of the site, this replacement process is critically important.

A small bur oak is fighting to establish itself on a prairie ridge as older oaks near the end of their lives. Both in the woodland and savanna portions of the site, this replacement process is critically important.

 

These beautiful metallic-looking flies were pretty abundant the day were at the site.  I saw several in the clutches of spiders, but didn't manage to photograph any of those.

These beautiful metallic-looking flies were pretty abundant the day were at the site. I saw several in the clutches of spiders, but didn’t manage to photograph any of those.

A close-up photo of bur oak leaves.

A close-up photo of bur oak leaves.

I'm not sure what species of bug (and it is a true bug) this nymph is, but it sure was striking against the green leaves it was feeding on.  I watched it repeatedly stick its long proboscis into this leaf as it moved across it.

I’m not sure what species of bug (and it is a true bug) this nymph is, but it sure was striking against the green leaves it was feeding on. I watched it repeatedly stick its long proboscis into this leaf as it moved across it.

Eastern redbud (Cercis canadensis) is a beautiful tree.  Both its pink flower and leaves are very attractive.  However, it is also one of the species we are trying to reduce the density of in the understory of the Rulo Bluffs woodland.

Eastern redbud (Cercis canadensis) is a beautiful tree. Both its pink flower and leaves are very attractive. However, it is also one of the species we are trying to reduce the density of in the understory of the Rulo Bluffs woodland.

This beautiful little brown snake was about 10 inches long.  I spotted it  as it was making its way through one of the areas Nelson had just shredded.

This beautiful little brown snake was about 10 inches long. I spotted it as it was making its way through one of the areas Nelson had just shredded.

There are a couple species of raspberries, or close relatives, at Rulo Bluffs, but I don't know what species they are.  This one was particularly beautiful the day we were there.

There are a couple species of raspberries, or close relatives, at Rulo Bluffs, but I don’t know what species they are. This one was particularly beautiful the day we were there.

Because of its long distance from our shop and field headquarters, we never feel like we spend enough time working at Rulo Bluffs.  It’s a beautiful site, and one of the best examples of oak woodland remaining in Nebraska.  As with other oak/hickory woodlands, however, it requires active management in order to survive and regenerate.  Without frequent fire, or substitutes such as thinning and shredding, the understory at Rulo Bluffs would become choked with small trees and shrubs, such as ironwood, dogwood, paw paw, and others.  Those woody understory species block light from hitting the ground, prevent the establishment of new oaks, and choke out most grasses, sedges, and wildflowers.  Eventually, if older oaks die without being replaced, these woodlands change into new communities, dominated by trees such as ash, hackberry, and others that don’t create leaf litter that can carry fire.  At that point, restoring the oak/hickory woodland community, which supports a much larger diversity of plant and animal life, is nearly impossible.

…and that is why we keep trying to find time to head down to Rulo Bluffs.  That, and it’s such a beautiful place.