Milwaukee Public Museum

by Andy Larson

EDITOR'S NOTE: This article is reprinted from LORE magazine (vol. 46, no. 2 (Fall/Winter, 1996), p. 18), a benefit of museum membership. ©1996 Milwaukee Public Museum, Inc.

A year ago this past May I was banding birds at Riveredge. It was near the peak of the annual spring migration and the trees bordering the river exuded birds. Few, however, flew down into the shrub layer where my mist nets were stretched waiting to intercept any passerby.

Returning from a periodic check of the nets, my son Eric, who was helping me, proclaimed, "I've got a bird and it might be one of yours." That was enough to raise the tenor of an otherwise slow banding day.

Eric thought the bird was mine because the its leg bore a small aluminum band. I lay no claim of ownership of the birds of the forest, but once one of my numbered Fish and Wildlife Service bands is placed on the leg of a captured bird a bond is established which makes the bird forever "mine."

Carefully, Eric recited the band number to me "1....8....6....0....3....4....8....4....6" as I checked the records which recorded the data on each bird banded. Band number, species, age, sex, molt and date are recorded at each encounter. I quickly located the record of #1860-34846, verifying that the band and the bird were mine.

The astonishing thing was that we had banded the bird two years earlier at nearly the same location. By "nearly" I mean within less than 30 feet!

Such proximity only hints at the amazing navigational skills of birds and the strength of the thread that ties them to a precise place on this vast planet. #1860-34846, a Mourning Warbler, was an international traveler from Central America, a neo-tropical migrant. And like all such avian migrants, it required no Visa or "Green Card" to take up a temporary residence in Wisconsin. Political boundaries, upon which humans place such emphasis, go unrecognized by the Mourning Warbler and its kin.

I like to think, although I cannot be certain, that "my bird," #1860-34846, wintered in the second growth forests of the Tirimbina Rainforest Center in Costa Rica, a tract of land owned jointly by Riveredge and the Milwaukee Public Museum. Implicit in that assumption is the fact that it had traveled more than 5,000 miles in its voyages back and forth from Costa Rica to Riveredge since I first banded it. Amazingly, it had accomplished these travels without road map or GPS system to guide it. Using only celestial bearing and a built-in magnetic compass, it had returned to a precise set of bushes along the Milwaukee River.

It is likely that #1860-34846's faithfulness to Riveredge as a summer home reflected a nest-site fidelity that gave it a reproductive advantage denied others. It knew, better than any newcomer, the location of the best nest site and where food was to be found.

The survival of #1860-34846 depended upon the preservation of the low, wet thickets of Riveredge Nature Center. It also depended on the second growth rainforest, if not of Tirimbina, than some place quite like Tirimbina.

Nearly all the neo-tropical warblers and other bird species such as Wood Thrush, Catbirds, Scarlet Tanagers, Rose-breasted Grosbeaks and Flycatchers depend on rainforests such as those found at Tirimbina for their winter home. Of the thirty-four species of warblers that occur in Wisconsin, at least thirty winter in Costa Rica. How many of those species are found at TRC awaits discovery.

The fate of #1869-34846 is unknown to me. I have not seen him since that May day of 1995 when we released him into the bushy shadows of the river edge. Perhaps he lurks in the thicket again this year and wisdom gained in past encounters helps him avoid my net. Perhaps he did not survive his annual round trip south and back. We are unlikely to find out, ever. Nonetheless, those brief encounters linked together distant corners of the planet into one home, a reminder that Costa Rica, Tirimbina and Riveredge are one thread in what is becoming increasingly evident is the tightly woven fabric of life on this planet.

There are other such threads.

Loafing along the shore of Lake Superior this past summer I paused to examine a group of aging maple trees that leaned into the wind. Their bark was ragged and as I discovered, covered with lichens. There were some that plastered the bark, crustose forms I remember being told in a botany class, others were more leaf like, foliose, and still others were branched like a miniature tree, a"fructicose" form. Together they clothed the tree bark coloring it a pale greenish-gray. Toward the ground the lichens surrendered their place to greener mosses, but they colonized the trunk as far as I could see into the canopy.

Finally I saw these lichens for what they were....ephiphytes. No sap sucking, energy robbing lifestyle for these lichen. They asked nothing of their host other than a place to rest. They were benign ephiphytes. It had taken Tirimbina help me see these lichens for what they were.

Two months previous I walked a gooey, clay-smothered trail that wound through the Tirimbina rainforest. I wondered aloud about the epiphytic plants the clamored up and over their host. In their abundance it was impossible to discern where one ended and the other began. There were mosses, figs, bromeliads, begonias, orchids and some lichens. These epiphytes were infinitely more abundant than the lichens on the bark of the maples I had examined on Superior's shore. In their abundance they formed aerial gardens where, I am told, resides much of the biodiversity of the rainforest.

Traditionally, epiphytes are considered a hallmark of the rainforest. High humidity, a nearly year-round presence of rain or condensation drip, coupled with the tropical warmth favor the profligation of this life style. The spare, when compared to the rainforest, growth of lichens on the bark of the maple reflects the rigors of life, the cold, the seasonality of the rains and ,of course, the long, dark winters.

That the Tirimbina rainforest and the forest trees bordering the cold waters of Lake Superior both were host to epiphytes suggests a common dictum, "Carpe Diem," which translates in ecological parlance to "seize the opportunity." Life survives by seizing the opportunity to exploit needed resources. Where resources are abundant, life is lavish. Where resources are limited, life is sparse.

The fabric of life is woven according to this dictum. The weaving is more intricate in the rainforest, less so in the temperate, but the final pattern is the same.

As the Museum's Rainforest Hall opened in November of 1988, I was exploring a rainforest not far from Tirmbina where the material for the exhibit had been collected. As is my proclivity I was looking for "bugs" -- cold-blooded things that crawl about on three or more pairs of legs. (Although this is not a very scientific definition of "bug," it does convey the catholic nature of my interest.)

Rummaging about in the litter of leaves, I encountered a millipede, a brobdingnagian millipede! One who, by Wisconsin standards, was raised on steroids. Its segmented, cylindrical body, with 2 sets of legs per segment, made it clearly recognizable. However, where Wisconsin millipedes are rarely longer than 1 inch, this tropical giant was fully 6 inches long. Giving it ample space -- for I knew that some millipedes discharge a toxic gas when disturbed -- I watched as it marched through the litter of the forest floor. Although silent, I knew its presence was felt by all.

Millipedes, whether in the rainforest or the deciduous forests of Wisconsin, fill a critical niche in the community. They feed on fallen leaves and as they do, so they create small windows or "fenstras" in the leaves. These windows open the leaf¹s succulent and nutritious interior to exploitation by fungi and bacteria. The fungi and bacteria, in turn, allow the nutrients once sequestered within the leaf to flow back to the soil.

Nutrients are the working capital of a community and, as such, must be kept in constant circulation for the economy to flourish. Bank to much of that capital and the economy slows and falters. A healthy economy depends then on the recycling of its basic raw materials: nutrients.

In an intact, mature ecosystem, the nutrients are continuously recycled with little loss to the system. In the rainforest, the "turn-over time" of nutrients is short. Hastened by the tropical warmth and moisture, a leaf rarely last more than 2-3 months. In a Wisconsin forest, this recycling is relatively slow, requiring a year or more. Its economy is tuned to a recycling rate, slower than the rainforest¹s, but no less balanced.

This, then, is what the millipede opened a window to...a balanced economy. This is this the nature of the economy that is revealed as one stands back and looks at the tapestry created by the interwoven threads of life.

This is the common nature of Tirimbina and the temperate forest of Riveredge for they are places where the fabric of life, which although perhaps worn, is still intact.