Thursday, July 07, 2011
I'm in Week 6 of my bird survey of super high quality awesome burned woods. Today I visited the flatwoods, last burned three years ago as part of a 2,000 acre burn unit. The fire burned upland flatwoods, dry and dry mesic sandstone and chert woodlands, and, as discovered today, a fen and a few big glades. We're at the end of the burn cycle here (the years elapsed between burns), a cycle that averages 3 to 5 years for quality sites (with dedicated managers); the woodies have a chance to grow up to a barely penetrable thicket in that time. So it was today, as I broke through the chest high post oaks and blackjack oaks with warm season grasses and super high quality forbs that soaked my torn khaki trousers to my knees.
If I've learned anything in this three year bird survey, I've learned that my observations mirror those of my inspirational predecessor, Terry Callahan, who surveyed the same site for an entire burn cycle to determine how populations change following a single fire event. I've never met Terry Callahan, but I've referenced his work in powerpoints, in published articles, in conversations, in presentations...if I ever meet him face to face, I'll hug and kiss him like he's an old summer camp friend. Rumor holds he's not working in the field anymore, which is a great loss for all of us.
Callahan's study in the mid 1990s showed that bird populations in burned woodlands are dynamic, that they change through the course of the burn cycle. The first year after a fire, indigo buntings are as common as deer ticks in deer infested woods. As the early seral stage sets in, the prairie warblers and yellow breasted chats move in with higher numbers than before; they take advantage of all the fruit bearing vines and shrubs like blueberries and raspberries, not to mention the insect life that comes to a rich herbaceous layer. At the end of the burn cycle, with the seral stage reaching about 6 ft. tall, summer tanagers, Eastern wood pewees, and chats dominate the landscape.
I love early seral situations in burn units and I love chats. I think chats have the silliest, most erratic and charming call of any other bird. I love that they're big and garrulous, that they crash through the shrub layer like a bull in a china shop, and yet they're warblers. My favorite bird, the chat, is the signature bird for the beautifully restored sites I work in, as they breed there along with summer tanagers, field sparrows, prairie warblers and Eastern wood pewees. The yellow breasted chat is the logo of my beloved local Audubon chapter, so I love chats even more than the rest. Prairie warbler is a close second.
Chats love the shrub layer. And today I was chest high in shrub layer post oak/blackjack oak woodland, all of which is surrounded by a rich understory of little bluestem, blueberries (ever so tasty), and an incredible assortment of high CC value perennial forbs. I went cross country through the shrub layer counting chats and tanagers, stopping for a long while to watch a beautifully mottled summer tanager perched on a 200 year old post oak sing his "chuk-burrrr" over and over.
When I sample these sites, the areas I'm birding where I also take vegetation notes, I make specific notes on the basal area, shrub density, and ground cover. Following the same sampling protocol that I have followed since I first moved to Missouri, I have to recognize that my total cover values in chat country will be higher than 100%. You see, beneath the stacked layers of post oak shrubs rests a super dense ground flora chocked of forbs, high quality forbs like Aster turbinellus, Penstemon tubaeflorus, every Desmodium in the woodland book (D. nudiflorum pictured--the flowering stalk is connected to the plant, but flowers almost a foot away from the base of the vegetative plant. Cool.).
[The Desmodiums are just opening up in Ozark woodlands, the plants that most people call "stick tights" because of the bean shaped seeds that stick to your trousers as you walk through August woods. The remarkable suite of summer wildflowers are in full bloom now, including everyone's garden favorite, Echinacea purpurea, found in low lying bottomland woodlands.]
One of the main reasons the area I'm working in is so rich with bird life is not just because of the small area of shrub layer woodlands I'm sampling, but for the 3,000 to 5,000 acres of restored woodlands all around them. Leave the early seral woodlands and the rest of the area looks like this:
No subdivisions in the way, no highway-sized bike trails so favored by citizens in my town, or even powerline cuts, just thousands of acres of restored woodlands. Fragmentation is a killer for bird communities, as the other studies I've read in recent years have shown, as well. Restore small patch woodlands, say 734 acres here, cross a recreational lake and restore another 300 acres, and you'll pick up more parasitic cowbirds than on a pasture. Oh, the good woodland guys are there, but in much diminished populations, and vying for viable nesting opportunities with hundreds of cowbirds in the mix. From my own studies, I've seen that large scale landscapes are the only way to protect declining songbird species. 40 acre burn units and areas surrounded by housing developments, highways, superfluous powerline cuts can sustain some nesting woodland birds, but not to the same degree as the larger areas, areas managed with fire at regular intervals, areas with integrity in the ground flora. As long as I live in downtown with my own little upland flatwoods (that I manage with fire)--surrounded by an abandoned lot and a daycare and a handful of other Craftsman homes, I'll never have a yellow breasted chat on my property. I have pewees and catbirds, but no chats. With my local city council cutting up every piece of natural green space in town for more trails (nature be damned), I probably won't see them anywhere in town anymore. At least I have great woods to visit in the Ozarks.
Posted by Allison Vaughn at 7:13 PM