The Bobolinks of Becker West

This summer I have spent a great deal of time trying to reclaim some savannas at our Becker West wildlife area that have become dominated by multiflora rose, honey locust, and several of the other typical characters found in formerly grazed land left to its own devices.


The site is a little different from some of our other areas. About 20 acres of the property is rented out for hay production. Just east of the hay field sits a roughly 13-acre reconstructed prairie. To the west, the ridgetops of savanna make themselves known with the presence of large wolf oaks and a grassy groundcover. North of the prairie and hay field, behind a 100+ year old fence, the habitat consists of mature timber with a dense, brushy understory.


Overview of Becker West; Pink = hayfield, green = prairie, blue = savanna

In other words, the site is a rich mosaic of different habitats. By sheer happenstance, it has also become a fascinating case study in the response of grasslands to a few different treatments – mowing in the hay field, fire on the prairie, and nothing at all (at least not for many years) on the ridge tops.

We humans, at least in the modern day, have a funny sense of self-loathing when it comes to our interactions with nature. Dating back the Leopolds and Muirs of the conservation movement, the idea that nature will do best when we keep our hands off it has deep roots.

But our thinking has evolved since the early 20th century. The evidence has become overwhelming that hands-off just isn’t possible, and might not even be as beneficial as we think. It just so happens, the Becker West wildlife area provides a prime example.

As I push my walk-behind mower (with the blade shut off) through the hay field, a seemingly impossible number of birds flush out of the ankle-deep grass. About half of them have a yellow patch on the back of their heads, and they scold me with a bright see-yew as they fly over the emerald hillside and disappear again into the clover and brome.


Hay field at Becker West

Bobolinks! Dozens and dozens of them! Not necessarily a rare bird by any means, but not something I had seen at Becker despite spending a great deal of time battling a patch of Canada thistle on the prairie adjacent.

That may seem odd. A wild animal seemingly showing preference for a largely man-made habitat. An investigation into the habitat requirements of Bobolinks suggests that they like tall vegetation, but here they are flourishing in a recently-mowed hay field and seemingly absent from the dense stand of 4-6’ Bluestem and Indian grass next door.


Prairie parcel at Becker West

However, that same investigation will reveal a few other key elements. No doubt one of the major factors at Becker is size. Bobolinks demonstrate something called area sensitivity, which means even though their individual nesting territory may only be a few hundred square feet, they prefer large expanses over small ones. Even though the prairie has sufficient size to house a bobolink or two, the hay field has almost double the area.

Furthermore, they have a preference for accumulated litter, precisely the type we had eliminated during a 2019 burn of the prairie stand (don’t worry, it will come back). They also have a low tolerance for even a few scattered shrubs or trees, like the locusts that seem to spring up like bamboo between burns on the prairie.  

In contrast to the prairie's 3-5 year fire intervals, the hay field only gets mowed. That leaves a good amount of accumulated litter for nesting habitat. Additionally, the mowing keeps the woody vegetation down all year every year while it only takes a year or two without fire for the prairie to have a few errant shrubs poking above the grasses.

It speaks to the role humans can play in enhancing biodiversity when we play our cards right. Left to its own devices, the prairie will shrink. In the absence of fire and grazing animals, trees will gradually colonize the sunny expanse and the bobolink habitat will give way to forest.


Bobolink

So we apply fire to keep the trees at bay. Indeed, fire is a major reason we have prairies in the first place. Moreover, compelling evidence has piled up to suggest that the pre-settlement fire regime was, like the hay field today, a man-made phenomenon. Indigenous peoples, for thousands of years, burned off prairies to encourage the fresh growth that attracted game.


In that way, they not only practiced prescribed fire, but prescribed grazing. Large mammals like bison and elk flourished – icons of America’s “natural” landscape – in part because of a heavy-handed input from humans.

Those large grazers – with or without human encouragement – also formed a pillar of grassland ecology that has largely disappeared from public prairies in Iowa. Bison have a real taste for grasses, and thus played a key role in the dynamic equilibrium of native prairies. By grazing down the grasses – which grow quickly and spread aggressively – the bison reduced their competition with native wildflowers and balanced out the vegetation composition.


Today, many prairie reconstructions in Iowa suffer from a dominance of grasses. We can set some of them back for a year or two with a well-timed burn, but they continue to come back and overwhelm the floral diversity.

It’s unlikely that any time in the near future will see bison roaming Iowa freely once again. But we do have a pretty abundant analogue in cattle. A lot of prairie managers have reservations about cattle, and with fair reason.

Cattle tend to travel single-file, creating trails while bison meander a bit more randomly. Cattle also congregate under shade trees and in water sources, concentrating their impact in a small area trampling tree roots and streamside vegetation.

Last but not least, many prairie enthusiasts harbor the opinion that cattle have a less discriminating diet than their bison counterparts. They fear that cattle will preferentially target wildflowers, thereby having the opposite of the desired effect of prescribed grazing.

More recent research has shown cattle diets to be remarkably similar to bison, all else being equal. Like with bobolinks, size matters. Cattle have a reputation as wildflower-eaters because they typically don't have enough space to be picky. Bison tend to have much larger territories, either naturally or artificially. Give cattle enough space and they, too, will demonstrate a preference for grasses that lets the forbs thrive.


Cattle grazing natives in Iowa

Surrounding states like Minnesota, Wisconsin, and Nebraska all have public land grazing programs. Resource managers for those programs tout their success in improving biodiversity and lowering maintenance requirements while providing additional acres for meat and dairy production.

But Iowa has comparatively little in the way of prescribed grazing on public land. Part of it stems from the paucity of public land - and the fact that most livestock operations have adequate acreage on their own. But some of it comes from that deep-seated reservation we have to actively engage with natural areas; that belief that generally, as humans, we just make things worse when we try to help.

That type of thinking causes us to forego useful tools instead of using them wisely. Doing nothing is a choice, too. We can't eliminate our impact entirely, and in many cases Pandora's box was already opened generations ago. Becker West demonstrates beautifully the fact that humans can help. We just have to show a commitment to understanding the dynamics and our place within the complex machinery that drives healthy habitat.


Timber stand improvement (TSI) at a Becker West savanna

Looking Back

The CCCB found many opportunities last month to celebrate one of the finest leaf seasons of the last several years. On October 10th and 11th, in lieu of Heritage Days, the Osborne Open Air Market saw dozens of vendors and hundreds of visitors squeeze the last of the marrow out of fall festival season.


On October 23rd, 12 people had the opportunity to create a beautiful work of art with the first in our Nature All Around Us art series. Painting with Abbey was a huge success! Stay tuned for future events on this website and our facebook page, as registrations are limited.


On October 24th, the 2nd-annual Pony Hollow Trail 15K saw runners from all over the state come and test their mettle on the flat, fast 9.3 mile course. We had two new course records set when Kyle Wagner won the men's division in a time of 55:41.1, and Olivia Dietzel broke the tape for the women in a time of 59:36.3. Find the full results here.


PHT15K champ Kyle Wagner leaving the pack behind

Looking Forward

November will also provide ample opportunities to get out of the house with CCCB events. First up, the harrowing tale of the Armistice Day Blizzard will be told on November 12th at the Osborne Nature Center. Registration is limited so call today to secure a free spot!


The first in our "Building Better Birders" workshop series, Kelly McKay of the Bio Eco Research & Monitoring Center will tell the story of his Christmas Bird Count Marathon on November 14th. Kelly has become a legend in the ornithological community for his commitment to birding, and you won't want to miss this deep dive into his life's work. Again, space is limited, so call ahead to reserve a spot.


On Saturday, November 21st, at 5:00 PM the Motor Mill Bridge Lighting will again see the fabled bridge adorned in holiday lights. Come on down to see the beautiful display and get in the spirit!


Finally, with Thanksgiving in the rear view, it will be time to think of the next holiday celebrations. We can help, and you can help us at the same time with Cedars for Celebration on November 28th, from 9:00-1:00 PM at the Osborne Pond. Eastern red cedars can quickly overwhelm grassland habitats, but they do make excellent pick-your-own holiday trees. Staff will be on hand with hand saws to help you locate and haul trees, but you'll want your own gloves and lashing material to get the tree back home. Trees are free but a suggested $10 donation to help with further habitat restoration efforts is appreciated.



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