Wissahickon Part 1: Houston Meadows

Bumblebee on goldenrod

Last Saturday (October 15) was an absolutely perfect early autumn day, with temperatures in the upper 60s, crystal clear blue skies, and very low humidity.  I packed Kali into the car and we drove over to the north-westernmost neighborhood in Philadelphia called Roxborough for a hike in the 1,800-acre Wissahickon Valley Park, Philadelphia's largest and best-known park.  Our goal that day, in addition to just getting some exercise, was to inspect Houston Meadows, a restoration project undertaken by the city's Department of Parks and Recreation as part of an ongoing series of natural lands restorations throughout the city's larger parks.

Trail through goldenrod and little bluestem

A few aspens; there are others growing nearby at the edge of the meadow

Native little bluestem (Schizachyrium scoparium)

To my mind, the Houston Meadows project was not a straightforward "winner."  During the early part of the 20th century, the meadows had been an active farm before urbanization expanded outward to the very edges of the city limits.  When the farm was incorporated into the park, the land became fallow and quickly reverted to herbaceous old-field habitat - a "wildflower meadow" in common parlance.  This habitat was extraordinarily attractive to birds and butterflies that needed such habitat, and Houston Meadows became a birders paradise maintained by fires set periodically by neighborhood hoodlums.

Bluebird box on meadow slope

All was well until houses were built up to the very edge of the park, and then the field fires had to be suppressed.  This fire suppression allowed natural succession to kick in and trees and woody vegetation, formerly killed by the fires, began to creep into the meadows, changing the land first to a thicket and then to a young woodland.  The birds and lepidopterans could no longer find appropriate habitat and abandoned Houston "Meadows."

Goldenrod (Solidago spp.), boneset (Eupatroium perfoliatum) and native grasses

With support from a philanthropic foundation, the city decided to try to restore the meadow habitat and attract the birds back.  So, they brought in heavy equipment to clear the trees in the young woodlands, and they seeded the land with early concessional meadow species and native grasses.    

The result has been mixed in my opinion.  First, I have to admit that I don't know if the "target" birds have returned to the meadows.  If they have, they've "voted with their wings" and given the restoration their approval.  But, if the birds haven't returned, the project cannot automatically be dubbed a failure because (1) they birds may not have "found" the meadows yet, (2) the habitat may not have developed enough to interest the birds, or (3) the restored field really might not be suitable habitat.

This section of the meadows almost looks "western," with a big rock and conifers

Where the herbaceous vegetation has gotten established, the meadows are lush, productive and beautiful.  But Parks and Recreation seems (to me, anyway) to have left too many trees in the midst of the fields.  Hawks and other raptors perch in these trees and prey on the meadow-nesting birds.

In addition, the meadows are small and fragmented.  Some meadow-nesting birds seem to need 160 acres of grassland habitat to breed successfully, and these fields are nowhere near that large.  Other species, especially species that like brushy habitat, may be the first ones to recolonize the site.  To my eye, the habitat looks perfect for birds that like scrubby, brushy habitat.

Deer exclosure fencing

Parks and Recreation also included a deer exclosure as part of the project, but it is in a wooded corner of the meadows.  I don't know the motivation for excluding deer from a meadow project, but perhaps they were trying to expand a section of woodland and not develop meadow here.

Regrouping on Meadow-nesting Bird Habitat

Between a pasture and a crop circle

Since 1997, our organization 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 a 160-acre 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 invited a respected field ecologist to speak to my restoration ecology class a few weeks ago about native grasslands.  This ecologist and I are good friends, and he has visited my preserve to consult on several occasions.  He also serves on the board of directors of another land trust in the region.  He told me that "his" land trust had had Eastern Meadowlarks nesting in native grasslands this summer, and he suggested that I talk to his land manager for some guidance.  So, I rounded-up my senior stewardship staff for a field trip and we paid a visit to the other land trust on October 30.  

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

Tom, the preserve'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 I do, so my staff should be able to do as well.

Crop circle (right) and native grassland (left)

My staff drew-up plans for our grassland modifications in the car on the way back to my preserve.  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 grasslands

A New Preserve to Explore

A sweeping view of hayfields at the ChesLen Preserve

On the Sunday afternoon before Memorial Day (May 26), Kali and I took advantage of the unusually clear, cool day to visit the relatively new 1,300-acre ChesLen Preserve located in central Chester County, Pennsylvania's "horse country."  ChesLen (so named because it is located in CHESter County and was donated by a philanthropist whose surname begins with LEN) encompasses fields, woodlands, wetlands, stream valleys, and a small section of a rare plant community that developed on soils underlain by serpentinite, an unusual rock formed under the ocean and that contains near-toxic levels of chromium and other metals.

We parked in a small lot near the southern end of the preserve and began our 3-mile loop walk by entering fields that gradually transitioned into woodlands.  The woods, relatively young second-growth forest full of the invasive plants that typify all second-growth woods in the northern Piedmont, offered pleasant walking.  While the preserve's excellent trail map only showed one trail threading through the woods, Kali and I found ourselves wandering on what was actually a spiderweb of trails throughout the forest.  We finally descended straight downhill on one of the paths to reach a pleasant, wooded tributary of the West Branch of Brandywine Creek.

Brandywine Creek tributary

Polywogs in a placid channel alongside the main stream

Directly across the stream we happened upon a scenic old fieldstone culvert bearing a trail (probably the remnants of an old farm road) over a rivulet.

Fieldstone culvert

After we crossed the stream, we walked through riparian woodlands for a short distance, then ascended the other side of the stream valley through expansive, open grasslands.  With clear, blue skies, a cool breeze, and expansive views, it was glorious; we felt like breaking into a song from the Sound of Music.

Kali ascending the hill through grasslands

Prior to becoming a preserve owned by the regional Natural Lands Trust (NLT) conservancy, ChesLen had been a private working farm.  To maintain the fields and prevent invasion by the non-native pasture-snatchers (e.g., multiflora rose, autumn olive, honeysuckle), NLT plans to continue to manage the fields through agricultural leases for the foreseeable future.

Because CheLen will become one of the NLT's signature preserves (both for its size and the diversity of habitats it protects), the conservancy recently completed a new visitor contact/public events/land stewardship center on a knoll overlooking the fields.  It's a classy facility reflective of the importance of the preserve.  The new facility will be dedicated in June.

New visitor contact/public events/stewardship center

A bit "raw," but impressive nonetheless

After a close-up visit to the new facility, Kali and I continued our walk through more meadows full of buttercups (Ranunculus spp.)

Buttercups along the trail

Fleabane (Erigeron spp.) hosting two native bees

The trail finally turned away from the fields and entered the valley created by the rivulet we saw flowing under the fieldstone bridge earlier in our walk.  We quickly found ourselves back at the stream we had crossed earlier.  We crossed the stream and re-entered the woods where we had lost our way at the beginning of the hike, finally finding the elusive trail junction where we should have turned.

May-apple (Podophyllum peltatum) with fruit on the streambank

Kali picking her way across the stream on natural stepping stones

ChesLen is a nice place, even if the vast majority of it is still devoted to active agriculture.  Our walk only covered a very small part of the trail system and there's plenty of interesting habitat to explore.  I just wish it weren't such a long drive (1.25 hours) from home.