Thursday, August 29, 2013

Of Birds and Men

Yours truly (left) with Pennsylvania Game Commission grassland bird expert Dan Mummert
For the last thirteen years, my land stewardship staff and I have been working to convert a 160-acre hay farm into native "warm season" grasslands.  Our goal has been to create habitat that will support breeding populations of "grassland obligate" birds - birds that nest in grasslands and in no other habitat.  Good examples in our area include Bobolinks; Eastern Meadowlarks; Savannah, Grasshopper and Vesper Sparrows; and Upland Sandpipers (admittedly a real long shot).

When we bought the property in 1997, the land was used to grow non-native "cool season" grasses that were harvested for hay.  We started small with our conversion; each year, we would herbicide a 10- or 25-acre patch of the pasture grasses, and then reseed the area with native grass seed.  In 2008 we finally finished the conversion by reseeding the final 50-acre patch.
The grasses have performed well, and our farm now looks much like a tallgrass prairie in the Midwest.  Though the grassland conversion has been very successful, none of the target birds have chosen to nest in the fields yet (with the notable exception of one very rare species that occurs in only a few very scattered locations in Pennsylvania - our resounding success to date).  We routinely observe Bobolinks and Eastern Meadowlarks stopping for a few days in the fields during spring and autumn migration, and each year we hope they'll linger to raise a brood, but inevitably they move on.
We have our suspicions about why they don't nest here.  The largest contributor to their decision may be that the fields are just too dense with grasses, and they can't find suitable small open patches in which to build their nests.  We know this is an issue, but there's a good reason why there aren't many openings in the fields:  we have an absolutely horrendous problem with non-native invasive plants. Any openings in the dense grass cover are quickly colonized by invasive plants, which then begin to spread and take over the grasslands.  So, we use herbicides to control the broad-leaved invasive weeds, which reduces competition for the grasses, and the grasses grow in to fill the openings.  Result: no nesting sites.
Grasslands with desirably diversity
Furthermore, the grasslands are not diverse and don't contain many meadow plants that would attract insects and pollinators on which the birds could feed.  Again, most of the good native wildflowers that we could seed into the grasslands would be killed by the broad-leaf herbicides we use to control the pernicious invasive plants, so we can't create a diverse meadow with a mixture of grasses and broad-leaved native wildflowers.  A 60:40 grass:wildflower mix is ideal; we probably have 90:10.      

Oh, and another thing.  Our natural area is in the middle of the suburbs.  We're largely surrounded by houses, roads, and businesses.  So our grassland is an island in a suburban sea, and it simply may not appeal to these grassland obligates that are used to wide open expanses of grassland in an agricultural matrix.
So, long and short, we may never be successful in getting grassland obligate birds to nest in our grasslands, but it doesn't stop us from trying.  One of our premier birders, Harris, called the Pennsylvania Game Commission when he learned that the commission employs a consulting grassland expert who would be willing to visit and share his knowledge and recommendations with us.  The expert, Dan Mummert, visited the natural area on Tuesday, August 27 and Harris and the staff escorted Dan on a tour through the fields.
From left:  Staff members Brad, Christopher, and yours truly; volunteer Harris; and Dan Mummert
Dan commended us for our success in establishing our grasslands in light of the nearly overwhelming pressure of invasive plants, and considering that we cannot use the two tools best suited to managing grasslands: prescribed burning and disking.  (We can't burn because of air pollution regulations and because the local fire marshals are terrified that we'll burn down million-dollar mansions on our periphery.  We can't disk the fields because we'd open up bare ground that would be colonized by invasives.)  
He did note that some of the grasslands contained wildflowers and that not all of the fields were grass monocultures; he encouraged us to try to create similar diversity in fields that were dominated solely by grasses.  He also recommended that we remove trees that had become established in fence-rows; the trees serve as perches from which raptors can survey the fields for prey, and the trees interrupt the "flow" of the broad grassy expanses the birds are seeking.  And last, but not least, he recommended that we consider closing some of our trails through the center of the grasslands during the birds' breeding season (May to mid-July) to limit disturbance by human activity.
None of these recommendations was new.  We'd had other wildlife biologists make similar suggestions in the past, but it's good to hear that everyone is "singing from the same hymnal."  We'll have to give all of these suggestions some thought since we have to weigh aesthetics, land management, and public use in our preserve.

8 comments:

packrat said...

Another really fascinating post, Scott. What an interesting dilemma. It even prompted me to begin thinking about what other options might exist to encourage nesting. Since I know nothing of these things I doubt I'll come up with anything.

Mark P said...

That's a pretty cool project. It's great that you try, despite the many obstacles. In some ways it's similar to the longleaf pine projects going on near us at Berry College. Our own, extremely tiny project -- our single little longleaf baby -- pales by comparison.

Scott said...

Packrat: The landscape around us "wants" to be forest. Grassland openings in the forest cover only occurred historically here when Native Americans burned, and later, after colonists arrived, when they kept an area open through agriculture and pasturing animals. We're really fighting a losing battle to try to keep this expanse open like this; we ought to just give in to Mother Nature's imperatives and let the area become wooded again. But, aesthetically, the land in native grasses is very appealing. And, then there's that (seemingly increasingly) off chance that we'll actually be successful, so we persevere.

Scott said...

Mark: You're pretty high up on your mountain, aren't you? At least that's the impression I've gotten from following your posts. All the longleaf pine woodlands that I'd seen (and, admittedly there weren't many) when I lived in Florida were on flat, sandy plains in the northern part of the state and in the Panhandle. Does your little guy have a chance there?

Mark P said...

We are at the top of our mountain, but that's not extremely high altitude. It turns out that around NW Georgia almost the only longleaf pines left are the ones on mountain ridges. I do think, though, that if you get much higher than this, it's too high for the longleaf.

Scott said...

Thanks, Mark. It sounds like prime longleaf habitat in the lowlands has been converted to other uses, and the trees only survive in refugia on the less fertile ridgetops.

Doug Marcum said...

Hey Scott, first of all, congratulations on completely restoring this habitat to native warm seasons grasses etc. While reading this all I could think about though is how fire is the key. You know this as well as I do - grasslands (especially in PA) are early succession habitats and the only way that they can be maintained as such is by continued disturbance. Seems like such a shame that you guys are forced to control woody succession by any means other than fire.

I don't know all the ins and outs of the grassland habitat management for purposes of grassland obligate species, but we have a large grassland in Cuyahoga Valley National Park which hosts all of the breeding grassland birds that you mentioned (besides Upland Sandpiper that I'm aware of). Funny thing is, we don't have many typical warm season prairie plants out there...just a lot of "weeds" and some nicer species mixed in really. There sure are plenty of Orthopterans for the birds to eat though!

We haven't burned this 100 plus acre tract yet, but that will happen soon. The plan is to burn it in thirds, rotating sections each year. I'm excited to observe the changes once we begin.

Anyway, just wanted to share some thoughts. Please keep us posted on this project!

Scott said...

Doug, I know the CVNP grasslands of which you speak. They replaced the Richfield Coliseum, didn't they? And, I knew they were attracting the grassland obligates, too! I'm so jealous!

Most of the forbs in our grasslands are also "weeds", too--mostly native ones, though, like goldenrods, asters, Indian hemp, and horseweed. As I mentioned, we've got to use broad-leaf herbicides to keep the invasives under control (especially Canada thistle), and there aren't many forbs that are resistant to Plateau. Black-eyed Susans, purple coneflower, and Illinois bundleflower seem to stand up to the herbicide pretty well, though.

And, our grasslands are full of Orthopertans, too!