Wednesday, May 16, 2012

Miniature Feeding Frenzy

I was reminded of big ocean fish and birds attacking a school of smaller fish from all directions. But in this case it all happened in a tree in my back yard.

For a fifteen or twenty minutes, a horde of warblers and gnatcatchers were harvesting bugs from every flower, branch and leaf. It was all happening in one small area (a few feet in all dimensions). Suddenly a humming bird was in the thick of this warbler and gnatcatcher frenzy. The hummer darted – back and forth, up and down, a foot or two in each dart, multiple darts per second – apparently catching small insects that the warblers were stirring up. The hummer acrobatics lasted for over a minute, which is time enough for the hummer to catch dozens of tiny flying prey.

The marauding horde of warbler species in my little yard this morning included:

Chestnut-sided warbler
Wilson’s warbler
Blue-winged warbler
Mourning warbler
Magnolia warbler
Nashville warbler

 Gnatcatchers, warblers and hummingbirds. Mini-sharks of the treetops.

White oak -- the living dead?

White oak is still a common tree. But less and less. It doesn’t seem to do so well in parks and lawns, and in the forest, while 200 and 300-year-old trees may be frequent, in most woods the young white oaks nearby add up to zero. They’re not reproducing, except in temporary situations.

Oaks need fire. Bur and scarlet oak thrive on prairie and savanna fire. White oak does not. Consider the ones planted at Somme Prairie Grove “by mistake.” Decades ago, long before the science of ecology had learned much, foresters trying to restore forest planted white oaks here with birch and silver poplar and other questionable companions.   Now white oaks here are starting to look like the one below.

A controlled burn last fall killed the lower branches, although you couldn’t tell that until spring when the live branches leafed out.

The fires here may be very good for Leiberg’s panic grasses, great spangled fritillary butterflies, smooth green snakes, orchard orioles and hundreds of other fire-dependent species of the oak savanna. But the white oaks are on the retreat. They’ll gradually give way to nearby bur and scarlet oak, wild plum, hazelnut, and other savanna shrubs, trees, grasses and wildflowers.

You see the future starkly in another part of the same preserve.

Two beautiful white oaks standing just northeast of tall grass (that is, dense fuel) were killed outright by a fire years earlier. On one level, it seems a tragedy that these fine old trees died, but on a more profound level, the important thing that’s happening here is that a rare ecosystem, supporting thousands of rare species, is coming back into sustainable balance. White oak is apparently just not part of the long-term healthy savanna – at least in this part of this preserve.

Where will such a noble tree thrive? Not in the unburned forests, where it can’t reproduce in the shade. Not in people’s yards, where landscapers recommended other species better adapted to lawns.

Perhaps in the open oak woodland, another rare and poorly understood community. Here the fires are not as hot; there’s less grass in the dappled shade. Often there’s a more rugged, fire-disrupting topography. Open oak woodlands have their own specialized, beautiful communities of birds, mushrooms, butterflies, wildflowers, ants, walking sticks, nematodes, bacteria and biodiversity heritage generally). 

We still don’t know what it would take to restore full health and a secure future to this important part of our planet. It will be fun to find the answers. And it will take at least decades, so let’s do it while the ancient white oaks we have left still have life.

Monday, June 22, 2009

rare plants and animals

Somme Prairie Grove in Northbrook, Illinois supports the following species of breeding "shrubland birds" or "open woodland birds" that are considered significant in this region:

American woodcock
black-billed cuckoo
yellow-billed cuckoo
ruby-throated hummingbird
eastern kingbird
brown thrasher
orchard oriole
rose-breasted grosbeak
great crested flycatcher
red-headed woodpecker

It also has nine populations of endangered or threatened plant species. I wonder if I should list them. Some conservation authorities suggest that their presence not be spread around. Unlike birds, plants can't get away if poachers come to pilfer them.

Do these birds and plants depend on each other. Ultimately, of course, all species depend on each other, but do these eight bird species depend on these nine plant species and visa versa? Or, for that matter, do they conflict with each other?

All the rare plant species would be killed off if the invasive weeds or shrubs in Somme Prairie Grove got too dense. All the birds listed above would lose their habitats if the shrubs and trees were mostly removed to benefit the sun-loving plants -- or if they were all left alone to grow as dense as they would without fire. Historically, fire (and animal impacts of various kinds) mediated the balance among these species. Now, decisions have to be made and priorities set by preserve managers. Which trees and shrubs should be cut? Should the stumps of all of them be herbicided? How often should controlled burns be conducted? How hot should the burns be? (A burn is orders of magnitude hotter on a hot, dry, windy day compared to a cool, damp, still day.)

The decisions also impact hundreds of species of butterflies, frogs, walking sticks, fungi, etc. etc. Are there good ways for the public to be informed advocates on such important questions? I hope so. If few people understand and care, the rare species and hundreds of other species here are doomed.