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Moving in, moving on |
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Living systems are never static. Whether in wild lands or residential landscapes, creatures are born and die, come and go, and with such flux no forest, field or flowerbed is the same from year to year. So it has been in the Ecosystem Preserve. Changes in the plant community have been readily documented, and the trajectory of change seems consistent (see “Changes on the Land, p. 22). Shifts in the animal community, however, are more difficult to track. Nonetheless, careful observation, with occasional assists from technology, has revealed a variety of comings and goings of which the following is a sampler. Over the past 25 years preserve watchers have identified 196 vertebrate species on the preserve. By their tally the preserve has hosted eight frog species, two salamanders, six turtles, three snakes, 146 birds and 26 mammals. Five fish species have been found in the various ponds. The totals provide a useful measure of the preserve’s ongoing diversity, but when species are traced from year to year, we find many transients. As habitats have changed, some animals have disappeared while others have moved in. Still other species have made brief appearances and then disappeared. Among those that have disappeared are the bullfrog and leopard frog. These animals were common when the preserve was first established, but as old farm drains filled, marshy wetlands became ponds and they disappeared. Similarly, as succession changed farm fields from grasslands to shrublands, once common bobolinks and eastern meadowlarks moved on. Perhaps most intriguing are the species that unexpectedly appear and almost as quickly are gone. In 1985, as we completed work on the trails system, an immature yellow-crowned night heron stationed itself in the pond at the north entrance of the preserve and spent three weeks fishing the pond. The bird was clearly outside its species’ normal range, but its ease with the place seemed a validation of the efforts made to establish the preserve.
A more recent transient was a pond turtle, the red-eared slider, which appeared in the pond outside the Bunker Interpretive Center in 2008. This turtle is not native to Michigan and has not been previously reported in the wild around Grand Rapids. For many years this species was a popular pet store offering, and many pet sliders have been released into Michigan waters where they have thrived. Such a release may account for the two large turtles that summered outside the Interpretive Center and then disappeared. List-making can be a compelling activity; just ask any birdwatcher with a life list. But lists are formed from incidental contacts with lives lived by means wholly outside the experience of the human observer. In that regard a species list can be an invitation to explore the lives the list hint at. If you are visiting the Ecosystem Preserve and want an idea of the creatures you might get to know there, visit www.calvin.edu/academic/eco-preserve/ for our species lists. —Randy Van Dragt
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