Reassessing the Raytharn Farm Grasslands

Between a pasture and a crop circle

Since 1997, the Pennypack Trust has been working diligently to create habitat for meadow-nesting birds which, as a group, are the most endangered suite of birds on the East Coast because of habitat loss.  Our strategy has been to establish native, warm-season grasses on the 160-acre Raytharn Farm we purchased that year.  Now nearly two decades into the project, we have a fairly respectable stand of native "prairie" grasses cloaking the land.  The grasses are beautiful (especially this time of year), resilient, and very popular with our visitors - but not with the birds we are trying to attract.  Eastern Meadowlarks, Bobolinks, and several species of sparrows stop in the grasslands during migration, but they never stay to breed.  What's wrong?  Didn't we do everything right?

Well, it turns out we didn't do everything right.  Grassland managers all along the East Coast have come to realize that the birds are seeking diversity - diversity in height and diversity in plant composition.  To the birds, our grasslands are too dense, too tall, and too monotonous, and they don't provide food (i.e., insects) in sufficient quantities for nestlings.

So, you might recommend that we diversify the grasslands, and you'd be right.  However, we also have a terrible problem with invasive plants.  The grasses can be treated with special herbicides that kill all invasive plants except the grasses, but there's no such "magic bullet" for diverse combinations of plants.  Once invasive plants colonize a mixed-vegetation meadow, control becomes much more time consuming and costly because the invasive plants have to be removed "surgically" without disturbing the desirable plants.  We've resisted trying to diversify our grasslands for that reason.

But, we've finally come to the realization that (1) we're not going to attract meadow-nesting birds if we don't do something different, and (2) if we can't attract meadow-nesting birds, why have the grasses at all because our landscape really wants to be a forest and we have to fight Mother Nature (i.e., natural succession) to keep it in grassland.

Fortuitously, I recently ran into Roger Latham, a respected field ecologist.  Roger and I are good friends, and he has visited Pennypack to consult on several occasions.  He also served on the board of directors of the Natural Lands Trust (NLT), which has preserves all over southeastern Pennsylvania and southern New Jersey.  He told me that NLT's Gwynedd Wildlife Preserve near Ambler had had Eastern Meadowlarks nesting in its native grasslands this summer, and he suggested that I talk to Gwynedd's land manager for some guidance.  So, I rounded-up Pennypack's senior stewardship staff for a field trip and we paid a visit to Gwynedd on October 30.  

Edge of the "crop circle" (darker foreground), native grassland (tawny center) and pasture (green, far left)

Tom, Gwynedd 's land manager had successfully created native grasslands like we had, but had also failed to attract meadow-nesting birds.  Then, he decided to create "crop circles" - round meadows within the grasslands that he seeded with a mixture of 16 different species of low-growing flowering plants (i.e., wildflowers).  Three years ago, he established about 10 such circles ranging in size from 0.25-acre to over 4 acres.  And, this summer, Eastern Meadowlarks nested in his preserve - not in the crop circles (and not in the native grasses), but in a pasture composed of non-native grasses immediately adjacent to the largest crop circle.  

Diverse crop circle vegetation (foreground)

Tom watched the meadowlarks build nests in the pasture (which is just as monotonous a monoculture as the native grasslands, but lower in height).  Then he watched the adult birds fly into the crop circle to catch insects that were using the wildflowers.  Success!

Crop circle (foreground), native grasslands (mid-ground), and woodland (background)

Tom's crop circles get colonized by the same invasive plant species with which we have to contend, but he told us that he is able to control the invasives before they become problematic with a combination of mowing before the invaders set seed, spot application of herbicide, and the judicious use of a string trimmer.  He's got a smaller land stewardship staff than Pennypack does, so Pennypack's staff should be able to do as well.

Crop circle (right) and native grassland (left)

Pennypack's staff drew-up plans for the Raytharn Farm grassland modifications in the car on the way back to Pennypack.  Stay tuned; it may be a year or two before we're successful, but at least we now have a plan!

 

Autumn color in the Gwynedd grasslands

 Submitted by David Robertson

 Executive Director