August Bird Disappearance Solved

Two weeks ago, I received an email with the news that the water birds had disappeared from Mountain Lakes Preserve. Might something have been applied to the water to remove algae, with unexpected results, or were geese, ducks and herons simply imitating the general human exodus from Princeton in August? My contacts at town engineering and Friends of Princeton Open Space knew of no chemical applications.

Carnegie Lake, too, was empty of waterfowl, other than a couple great blue herons. One heron flew across the lake, flushed another near the opposite shore, chased it a short distance, then returned across the lake, flying low, its wingtips touching the water.

Smoyer Park's pond also was clear of geese. Had they finally taken note of the signage?

Maybe the fisherman's dog had scared the geese away.

The dog, upon closer inspection, turned out to be 2-dimensional, a metal dog profile placed there by the company contracted to periodically (futily?) scare the geese away. The fake dog looked to be faking out the geese, but the fisherman was skeptical, and told me the geese will soon be back.

Some responses from people in the know, plus some internet research, helped make sense of it all.

Plainsboro Preserve director Nancy Fiske forwarded a response from Scott Barnes, head of New Jersey Audubon's All Things Birds division:

"Most waterfowl tend to molt in late summer and are flightless for a brief period of time, during which they are secretive. I've seen typical numbers of geese around locally in the last few weeks; it may just be they've moved of a particular water body in Princeton. Geese will often change habits and feed at night around the full moon. As for herons and egrets, late summer is a time of wandering, where both adults and juveniles will move about from place to place taking advantage of local food sources and concentrations of fish at ponds/lakes with lower water levels."

Stephanie Fox, naturalist with Delaware and Raritan Canal State Park, added, 

"as for Herons, I believe they are still able to fly, but just not so efficiently, so they also try to hide out in less conspicuous areas until they have their full set of flight feathers."

That could explain why the great blue heron seemed to be struggling to stay above water, and perhaps it was acting territorially towards a young whippersnapper encroaching on its part of Carnegie Lake.

For those uninitiated in the ways of birds, like me, some general info about molting is at this link. The distinction between the "sequential molt" that most birds undergo, and the "simultaneous wing molt" characteristic of ducks and geese, can be found here. 

Thanks to Elliot for alerting me to this seasonal exodus. It would be interesting to find out where the birds go to be safe during molting, and whether it's one place or many.

Towpath Walk This Sunday, Aug. 28, 8:30am

Time for the annual nature walk along the loop trail next to the towpath. We'll meet at 8:30a this Sunday, August 28, along the towpath just west of Harrison Street, where there's a nature trail sign. All are welcome.

We'll catch the overlap between August and September flowers, as JoePyeWeed, ironweed and cutleaf coneflower transition to goldenrods. The wildflowers were getting mowed down until 2006, when I was able to talk DR Canal State Park staff into cutting back on the mowing. The park staff reduced mowing to once a year (less work!), added a broad, well-mowed trail that runs parallel to the main towpath, and the native flora has responded by growing in greater abundance each year.

The nature trail threads through Princeton's closest approximation of an oak savanna, where there are enough openings between trees to allow summer wildflowers to prosper underneath. All of these Hollow-stemmed Joe-Pye-Weeds are facing north, towards a gap in the tree canopy.

We'll see how natural and cultural influences--from canal building to hurricanes--have combined to shape this diverse, dynamic floodplain habitat.

Parking: There are two small parking lots at either end of the Harrison Street bridge. More distant parking is in the Lake Lane area, just off Harrison St. north of the lake, and at a lot on Washington Road just south of the towpath. If you get there late, it should be easy to find us along the trail loop. This link should take you to a map.

Sensational Year for Floodplain Wildflowers

If only buildings loved this summer's heavy rains as much as these floodplain wildflowers do. Wild senna has never put on a show quite like this.

A variant of Hibiscus moscheutos is turning on the pink.

Joe-Pye-Weed is flourishing.

Just one stalk of a 9 foot high cupplant would be enough for a bouquet.







The cutleaf coneflower and late-flowering thoroughwort combo has turned the backyard yellow and white. And the pollinators are just lapping it up. A number of factors make these lowland wildflowers easy to grow. The soft ground and the exuberant growth of the desired plants makes weeding easy, and the species shown lack the capacity to spread with rhizomes or stolons, making it much easier to keep the garden in balance.

Capturing Runoff at the Shopping Center

What is soft rush, a wetland species, doing outside the entrance for Ace Hardware at the Princeton Shopping Center? Look up and to the left and you'll see the awning that spills lots of water onto the walkway during rains. The concrete absorbs the impact and the water then makes haste to the bed of rushes, where much of it is absorbed. Pretty clever. Soft rush is evergreen, so should provide some color even during the winter months. We'll see how it weathers the salt and snowplows that stray off course.

Just down from the rushes is a parking lot island. In the past, these islands would have been built higher than the surrounding pavement, and spurned the runoff. But some of the new islands have notches in the Belgian Block curbing where runoff can enter, seep into the ground and feed the plantings.

All of this means a little less of the shopping center's massive, unfiltered runoff goes thundering into Harry's Brook, a few hundred feet away where the brook becomes a brook in Grover Park.

See a previous post that compares the shopping center's parking lot with a more advanced design at Westminster Choir College.

Check Your Viburnums for Imported Leaf Beetle

The list of destructive, imported insects affecting Princeton is getting longer. Most people are aware of the gypsy moth and the Emerald ash borer. Add the Viburnum leaf beetle, which skeletonizes Viburnums in people's yards and in the wild. A post in May last year documented the larva chewing on a Viburnum in Princeton's Harrison Street Park. I killed every larvae I could find, and haven't seen a recurrence this year. But badly eaten leaves on a Viburnum in a friend's yard in nearby Lawrence this summer mark a second sighting, this time with damage coming from the adult beetle.  

Here's what appears to be an adult on a Viburnum commonly called highbush cranberry.

They do a thorough job of it. Completely skeletonized shrubs seen in Pittsburgh years ago were a chilling omen for what could happen throughout the eastern U.S. It should be noted, in this age when so much focus in the news is on intentionally destructive behavior, that the greatest damage to our world is being wrought completely without malice, as insects and diseases hitchhike on transported nursery stock, and the products of combustion slip silently, invisibly from our exhaust pipes and chimneys.

An arrowwood Viburnum (V. dentatum) in my backyard is showing early signs of an infestation. These are two of the most susceptible species of Viburnum. The most striking incidence of arrowwood Viburnum in Princeton is in low woodlands along the DR canal. Despite growing in deep shade, it can have surprisingly showy clusters of white flowers in the spring. Sad to think those spring vistas could become a thing of the past.

If you check any backyard Viburnums you may have and find early signs, you may be able to limit next year's damage with some of the techniques described at this link.

The blackhaw Viburnum, our most common Viburnum in the wild, is less susceptible.

Native Plants Featured at the Olympics

The Olympic opening ceremonies in Rio included a big surprise. After some spectacular visuals and choreography with a cast of thousands, the stadium darkened and a solitary boy walks across the stage. He encounters, of all things,

a plant, and thus starts a segment on climate change, with maps showing the coastlines of the world that will be swallowed by the ocean, the shrinking ice cap, and a visual conveying the warming atmosphere over the past century.

Most people think of plants as mere ornament and background for human endeavor, but here was a plant, a Brazilian native plant, no less, front and center, drawing the spotlight. It's one of the great paradoxes, that humanity's first line of defense against the planet's greatest threat is not our militaries, but, of all things, plants. They'll never win the 400 meter, or dazzle on the parallel bars, and many kids graduate from high school knowing little about them, but as brilliant chemists that tirelessly eat carbon dioxide, plants have everything to do with winning the marathon to keep our planet livable for generations to come.

And there they were, later in the evening, next to the flagbearer for each nation entering the arena, native plants of Brazil being carried by a child. A whole forest will be planted, with one plant for every competing athlete. Symbolic, to be sure, contrasting starkly with the environmental realities in Rio, but moving nonetheless.

In this photo, the plant fronting the U.S. athletes is a green flash on the right, with Michael Phelps bearing the flag in the background.

It felt like a gamechanger, as if the world is making a pivot and starting to get its priorities straight. That plant in no way compensates for the human combustion-fest of bright lights and fireworks, but at least it's there, with its humble, heroic chlorophyll, unmatched in its chemical prowess, to remind the athletes where their inhales come from and their exhales are headed.

Before and After the Flood at the High School Wetland

Many have seen the video of the extraordinary flooding at Princeton High School on July 30. As something of a citizen "activator", and high school parent, I'm meeting with school and town to help give momentum to a lasting solution to prevent future flood damage to the school.

I hope the school's basement and performing arts stage prove as resilient as the wildflowers in the ecolab wetland, which happen to be in full bloom. First photo is a "during" shot, showing the Joe-Pye-Weed and Rose mallow hibiscus sitting in five feet of floodwater.

This second photo shows the plants the next day, happy as clams, as if refreshed from a nice long bath.

This is a great time to stop by and take a walk around the perimeter of the wetland, and maybe catch the sunset in the big sky over the ball fields just on the other side of the performing arts wing from the wetland, on Walnut Lane.

Towpath Nature Trail Loop:
Another great place to see these beautiful summer wildflowers is along the nature walk created and maintained by the DR Canal State Park crews. Get on the towpath at Harrison Street and look for the Nature Trail sign. A virtual guided walk can be found here. This link should take you to a map.

Delight and Tragedy in a Summer's Downpour

Water's capacity for delight and destruction was on full display yesterday during an extraordinary downpour. It provided definitive proof, as if any more were needed, that we must work with nature rather than against it.

When the rains began, I was just finishing an enjoyable tour of my friend Suzy's garden in Lawrenceville. She brought me in to consult on what plants to keep and which to remove. Suzy was one of the founders of the Whole Earth Center, nearly 50 years ago. The rain provided a chance to see how her roadside garden captures and channels runoff from the street.

Using stones to manipulate the water's flow, her gardener Andrew Thornton has created whimsical, Inca-like channels for the water to follow, feeding the native sedges, ferns and wildflowers as it heads down the slope.

The rain got very dense, and I retreated to my car to drive home to Princeton. Coming up 206, the street had already become a river, even though I knew the worst of the storm was yet to come. I began to think of places to go to see what the water was doing. The middle of a storm, if there's no lightning, is the best time to check out Princeton's water works, or water wrecks, depending.

Then I remembered the high school, and had a sense of foreboding. The school had flooded in 2009, due to poor design of an addition along Walnut Street. The basement, cafeteria, hallways and offices were flooded, and the performing arts stage had to be replaced. I had repeatedly warned the various powers that be that a repeat was very likely, and had offered a solution, but no action had been taken in all of those years. This storm felt very much like 2009's.

I arrived to find Walnut Street completely flooded. When the underlying stormdrains are overwhelmed, the street becomes a river that actually flows towards the school. That's the performing arts wing on the right, and the detention basin/wetland on the left. People have tried to blame the wetland plantings in the basin, but we have shown that the real problem is that Walnut Street is higher than the school. 

Water flows downhill, and went straight from the street down into the school's basement. In the past, the facilities crew has placed sandbags here to block the water, but staff probably live too far from Princeton to respond in time to a sudden storm. And it was only a matter of time before that bandaid approach would fail.

Some of the water from Walnut Street seeped under doorways and into the bandrooms and hallways.

Here, I found, was an entrance on the north side of the performing arts wing that led directly to the wooden stage. The drain that would normally take this water away was overwhelmed and useless. Will the stage be warped by the moisture, and have to be replaced yet again?

In the middle of this photo, taken nearby at the entryway to the performing arts center, you can see water coming out of the drain, rather than disappearing into it. Overwhelmed, the drains actually begin contributing to the flooding.

The wetland is in full bloom, and the plants should be fine. Despite their seeming mass, they do little if anything to affect the capacity of the basin, which was not designed to hold water coming in from the street.

What prevented even worse flooding was the driveway across the street leading into the Westminster property. A PHS science teacher, Tim Anderson, and I had recommended to the school that the curb on the Westminster side of Walnut Street be lowered, so that water, instead of flowing into the high school, could be channeled safely away,

into the Westminster's big field. That field, too, could be planted with beautiful sedges and wildflowers, like the PHS basin/wetland. The field is a designated wetland and cannot be developed, and Westminster Choir College would be motivated to assist, given its periodic use of the high school performing arts stage.

I hope our proposal will now be taken seriously. Risks of PHS flooding would be greatly reduced, and the neighborhood would become even more attractive and colorful. Big storms will bring not emergency workers but neighbors out to see water working its wonders in nature's garden. Work with gravity, work with nature. Please!

Update: The high school's wooden stage did in fact sustain water damage and had to be replaced--for the second time in five years. Here's a widely viewed video of floodwater cascading down into the high school basement.

Changing of the Guard in the Backyard

There's a changing of the guard in the garden, that is, the guardians of nectar. Flowers of July--Culver's Root, beebalm and tall meadowrue--are yielding to some of the flowers of August--rose mallow hibiscus,

cutleaf coneflower,

and Joe-Pye-Weed.

Meanwhile, a young American elm, so appealing in its shape and ambitions, has designs on the sunlight the flowers have had up to now. This is a guardian of a different sort, a guardian of shade, which means there's a decision to be made, sooner or later, between one and the other, by the guardian of balance.

When a Leaf Is Not a Leaf, and a Grass Is Not a Grass

The kids were having a gas, literally and figuratively, up at Hilltop Park last week when I went to lead a nature walk for Stone Hill Church's annual summercamp. Our Friends of Herrontown Woods nonprofit has been partnering now and then with Stone Hill Church, which borders Herrontown Woods up on Bunn Drive. Not easy to compete with bubbles on a summer's day, but even in a park that's mostly turf and trees, there's always some aspect of nature to point out. One of the counselors noticed large dragonflies cruising above the lawn, probably munching on tiny insects as the campers paused to eat their own snacks. I showed the campers how to identify a white pine (needles in clusters of five, just like the number of letters clustered in "white"), and how to tell that what looked like seven leaves on an ash tree was really only one compound leaf made up of seven leaflets. Tricky stuff.

A closer look at the ballfield revealed that what looked like grass wasn't necessarily grass. If you see light-green splotches in lawn this time of year, chances are you're looking at nutsedge, which looks grass-like but is actually a sedge. And how do you tell a sedge from a grass?

Pull one up, look at the stem and you'll see it's triangular. Roll the stem between your fingers and you'll see and feel that "sedges have edges"--the three edges of a triangle. Most sedges are native perennials typically found growing in wet ground, but the nutsedge is a nonnative that spreads quickly through gardens. Chances are, the kids could go home and find nutsedge invading their parents' garden. (see last photo in this post)

Another weedy plant flourishing in the ballfield was a round-leaved creeper named ground ivy or gill-over-the-ground.

Here's how it spreads, by sending out shoots above ground that make new plants. This weed too is common in gardens. If you want to prevent it from coating the ground, it's easier if you pull out the new extensions before their roots get too established. One could say its presence in the field is good news, in that it indicates that broadleaf herbicides aren't being sprayed on the grass.

Here's the typical look of nutsedge spreading through a garden. It lifts pretty yellowish seedheads to the sky while sabotaging the intended neat formality of a row of Liriope.

Later on, the campers got to appreciate nature in another way, sitting in the comforting shade of an ash tree while listening to a fireman talk about safety in the home.

Why the Native/Non-native Distinction Matters

Here are two examples of leaves being stripped by insects in the backyard. One example is likely harmless, and actually shows that there's a functional foodchain in this backyard habitat. The other signals the arrival of yet another severe blow to our local ecology.

Most people recognize jewelweed, the annual with tubular orange flower that feeds hummingbirds, and has a fleshy stem that some use to rub on poison ivy skin rash. The flowers hang like earrings, and turn into spring-loaded seedpods that are fun to put in the palm of the hand and explode. Used to seeing it grow robustly in low wet areas, I was surprised this morning to find one defoliated.

A few new leaves had sprouted from stems made bare by a caterpillar.

Closer inspection showed a busy caterpillar on the underside of new leaves. Some internet research (here and here) suggests there are several species of moth that feed upon it.

Though this one plant was defoliated, others in the garden are prospering. If the caterpillar is native, one can assume it's been consuming jewelweed for thousands of years, and so poses no threat to its favored plant species' survival.

Here is a much different situation--an arrowwood Viburnum showing signs of insect damage. Chances are good that this native Viburnum, which has flourished for a decade in our backyard, is not being eaten by a native insect with which it has coexisted for millenia. More likely the hungry caterpillar is the Viburnum Leaf Beetle. Imported from Europe, it has been spreading across the eastern U.S. Since it did not evolve here, the native Viburnums have had no chance to develop defenses to limit its consumption. As with the Emerald Ash Borer that is beginning to devastate our ash trees, the introduced Viburnum Leaf Beetle will likely cause radical changes, not only in our forests but in backyards as well.

Local nature, in effect, is sustaining one body blow after another, due to the introduction of non-native species, some of which unleash radical change. It's important to note how our world is being transformed by unintended acts while the news media focus on intentional acts of destruction. If a rogue arborist began randomly cutting down people's trees and shrubs, there'd be a great outcry and the destruction stopped. But if an accidentally introduced insect does the same, causing millions of dollars in damage, its accepted with a shrug and a sigh. Add the collateral damage known as climate change into the mix, and you see how profoundly vulnerable is our world, no matter how big the military or well trained the police force.

A useful approach to defining "native": 
There's a lot of confusion about what the word "native" means, and why it's an important distinction in ecology. Some contend that all plants and animals are native to the planet, and so all species should be welcomed everywhere with open arms. That supposedly openminded point of view requires denying the reality of co-evolution. It's really quite simple. When plants and animals evolve together for thousands of years, they adapt to each other's presence. A balance develops, in which plants evolve chemical or physical defenses that discourage animals from eating them into oblivion. Animals, in turn, develop the capacity to crack those defenses sufficiently to get the food they need to survive. There's a balance of consumption.

Here's a well-written column explaining how differently a plant like garlic mustard behaves where it evolved, vs. after being introduced to a new continent.