May 18th, 2007

woods, Elizabeth, camera, April

Habitats, Etc.

We all live in habitats, and all our habitats are subdivided into microhabitats.   Wildlife are the same.  For most of them, they utilize a variety of microhabitats in the range of their overall habitat...a hispid cotton rat may live in grassland, but it chooses particular parts of that grassland for its burrow, its traveling trails, its food supply, its water supply.  Animals  that appear to share the same place may actually be recognizing different habitats--as people living in the same city may use and experience its offerings very differently (do you go to bars or museums--or both?  Do you go to classical choral concerts or rock concerts?)  A block of woods that looks like any other woods to the human passing by may offer unique habitat to one bird, and discourage another.

Habitat includes not only space but resources in that space--food, water, places to rest, to hide, to breed, to raise offspring.   We are lucky in that our otherwise "plain" 80 acres offers three distinctly different habitat types (riparian woods, upland brush/woods, and grassland) and many microhabitats within each of these.   These habitats each attract a unique mix of species, and changes in the proportion of woods to grass or brush to woods will affect what we see--what wildlife we 'manage'.  That's why "habitat management" is an important part of wildlife management.   The  choices we make--not only how many acres of grass, but which grasses, how thick, and what forbs we encourage/discourage with the grasses--will determine  what can live there.  The choices our neighbors and sociey make (whether to subdivide neighboring property, whether to use it for pasture or cultivated crops, stocking rate, whether to build a road next to our fence, etc.) all affect what we can easy or hard it will be to maintain a healthy mix on our land.  On big properties--thousands of acres--the "neighbor effect" is smaller but still important...upstream neighbors are more critical because their management of the water there determines what happens to your creeks, seeps, springs, and the amount and kind of runoff you get.

My ecology prof said that water management was the key to land management, and the rules of water management were simple to state.   "Keep the rain that falls on your land on your land.   Slow the water down: if water runs off your land at all, it should be cleaner than when it started.  This is true whether it's your runoff or runs onto your land from somewhere else.  Ideally, all run off would be clear--no sediment.  If you manage the water, the land will take care of itself." 

We've been working toward that for six years now.  Building check dams and gabions to slow surface runoff, planting and otherwise encouraging vegetation (which resists erosion and also filters runoff, building soil rather than taking it away.)   Areas that were bare six years ago are now covered with vegetation, and more of the vegetation is native.  Most surface  runoff is clear (and there's less of it.)  Here's one result:

  The rock checkdam (lleft side of picture) controls headward erosion of the natural drainage channel...which used to be a bare, eroding scrape for about a quarter mile.  The area around it, alternately bone dry and boggy, supported only low-quality forbs that could not resist erosion.  Now it's mostly grass and water stays in little pools to support wildlife and keep the soil moister between wet seasons.  Except in floods, when dirty water pours off the highway (behind the camera) the water is clear.  Yesterday, it had damselflies and dragonflies over it, and various aquatic insects in it.   In the distance is the rocky lump with the "dry woods" (brush and trees in clumps, grass and forbs between them.)

woods, Elizabeth, camera, April

In defense of brush: a habitat issue

I grew up in South Texas, much of which was covered at that time (and more had been) by vegetation known as "brush."   Already it was getting rarer, but it consisted of low woody plants, often in clumps, cactus, short bunch-grasses, and forbs.  It was all drought tolerant (almost everything could, in really bad droughts, drop its leaves and play dead for six months to a year, and come back none the worse.)   Most things had thorns and/or tasted bad or had thick bark.   Mesquite you've all heard of, along with prickly pear and yucca, but some of you may not have heard of huisache, guajillo, retama, ebony (not "real" ebony--anothe legume tree), and many other brush-country plants.   

Some people--possibly most--considered it useless.  The trees didn't grow very tall (we called any woody plant in whose shade you could sit, a tree), and there were all those thorns, and it was hard to get through the  why not root-plow it all away and plant nonnative grass instead?  Why preserve any of it?   The wildlife that called it home--the songbirds that nested in it, the game birds that used it for cover and ate the seeds that fell, the very rare and beautiful small wild cats (ocelet, jaguarundi), the natives--they knew what it was for, and when it was gone, they began to diminish.

Other parts of the country also have brush--some call it thickets or scrub or chaparral--thick clumps and masses of woody plants mixed with grasses and forbs, and a nuisance to the person who wants everything groomed and tidy.  But wherever you have brush, you have wildlife.    Of our ~80 acres, about nine and a half, perched on a rocky knoll too thin-soiled to grow useful grass, is brush.  A few pockets of deeper soil hav allowed the trees to grow taller,  but a lot of those taller trees have died out in the past 15-20 years.   The plant species overlap those in the riparian woods a few hundred yards away, but there are distinct differences.  Only the brush has kidneywood, paleleaf and twistleaf yucca, Texas persimmon.  Only the riparian woods have black willow, American and slippery elm, and eastern persimmon.  The difference is largely water, but also soil depth. 

Within that ~9.5 acres are patches of bare, hard, flat rock (right now covered with brilliant yellow stonecrop in full bloom) and areas of broken rock or gravel with low bunch-grasses and forbs, and scattered clumps of stunted oak, cedar elm, hackberry forming the nucleus for other woody plants: Texas persimmon, the yuccas, woollybucket bumelia, elbowbush, Mexican buckeye (not a true buckeye), prickly ash, aromatic sumac.  Open ground between has the grasses and forbs, providing brilliant color in early spring if there's rain.  There are three kinds of cactus: prickly pear, horse crippler, and plains nipple cactus (very small, noticed mostly when it blooms.) 

  Here, between brushy  clumps, are Drummond's wild onion, bluebonnets, greenthread in bloom, with some Texas star blooming in the background--the green bush on the left is elbowbush (a distant relative of ashes and olives) and you all recognize the prickly pear, I'm sure.   As the season progresses, and if rain permits, a sequence of wildflowers keeps butterflies, flower-feeding moths and syrphid flies, and even hummingbirds happy.

  This is a winter view of an area where we feed winter-resident songbirds.  The low tangle of branches is elbowbush...birds can feed in there and be safe from aerial predators (we have several species of falcons and accipiters in the winter) while enjoying the warm sun.  I like it because I can watch them right through the bare branches and twigs, while they feel safe and feed normally.  For storm shelter, they have the dark green Ashe junipers (left and right).   We often have 40-50 birds of half a dozen species feeding in there at once.  Most of our winter-resident migrant birds prefer the brushy acreage to anything else on the place.

  Here the elbowbush is in full leaf in May--its flowering over, its berries still tiny green nubbins--and its intricately tangled branches and thick cover to the ground provides nesting and feeding cover for the summer-resident songbirds. Is there a bird in there?  I don't know unless it sings--no penetrating that solid mass of leaves.  Elbowbush also has sweet berries which some of the songbirds relish.

I love brush.  I also like grasslands and woods, but I truly love brush.