A few
years back some of our local birdwatchers found a mountain chickadee. Normally
found in the mountains of the western United States, it was quite unexpected. I
didn't rush out to see it like most of the birders, but instead it lead to some
contemplating and theorizing.
Why have
Mountain and Carolina Chickadees and White-breasted Nuthatches appeared in
Midland. The first thought – this
chickadee was in an oak tree. Were the
others also in oak trees? Yes, they were
first found in areas of the city where there are many live oak trees, and each
of them foraged in oak trees much of the time.
In the Hill Country Carolina Chickadees live in oaks; in the mountains
of West Texas, Mountain Chickadees live in oaks. Shin oaks, the only oaks in Midland County
before landscaping with oaks became popular, are usually less than five feet
tall and have no chickadees. They prefer
tall oaks and if we had no big oaks, the chickadees would not stop over in
their wanderings.
That is
a thought that needs to be pursued – chickadees wandering. Why would they? Why would they leave their
preferred ecological community? They are
not migratory. Was there an ecological
catastrophe? No, no fires, no mass
habitat destruction of any sort in their homelands. Would chickadees leave because there were too
many for their habitat – did every fledgling survive in a bountiful
spring? Could a droughty fall have
caused the food supply to be inadequate for a bumper crop of chickadees? Could it be that a percentage of the
population of chickadees is genetically programmed to seek out and find new
chickadee-friendly habitat? Or could a
few just have “worms in the brain” and behave in un-chickadee fashion?
Could it be that oaks have
introduced other fauna and flora to Midland? Many of the oak trees in Midland
were dug up in the wild and transplanted.
With the soil around their roots came a number of other plants. The most common is Briar. Usually the homeowner chops it down, but in
more informal landscapes a number of the Briars have been allowed to grow. They produce berries and birds have spread
them. Mistletoe grows on oaks and its
berries are designed to be spread by birds.
Mistletoe berries are composed of a very sticky liquid. If a bird that has been eating them cleans
its bill on a branch, a seed hanging to its bill will be glued to that branch
and another clump of mistletoe started. Carolina snailseed, a vine with red
berries, may have arrived with oaks, as did poison ivy.
Oak
Decline, a disease of oaks, have been recorded.
The disease may have come on a wild dug tree, or in oak firewood. Firewood has also introduced several types of
fungus, lichens, moss and algae. In old
firewood and in rootballs, imported fire ants keep arriving in Midland. So far fire ants have been found here only in
disturbed and irrigated soil in town. No
fire ant mounds have yet been found in pastures where soils are harder.
Many new
species of gall forming insects also arrived with the oaks. Over 800 species of gall insects live on
oaks. Most are tiny wasps but gnats,
midges and flies also cause galls. (Do
chickadees eat these gall insects? Do
they break open the galls to eat the larvae?)
Aphids and scale which attack oaks have also arrived.
What
about vertebrates? Did the Mediterranean
Geckos that have proliferated the last few years come in the oak trees? Did the Gulf Coast Toads at Hill Park arrive
in an oak rootball? How about Green Tree
Frogs and the Green Anole?
Nuthatches,
creepers and kinglets, gleaners all, rejoice in bark crevices laden with
insects associated with oaks. Acorn and
Red-headed Woodpeckers feast on acorns.
Forty years ago there were no Blue Jays in Midland. Now they remain all year. Acorns are one of their chief foods. The winter population of Yellow-rumped
Warblers has quadrupled since the 50’s and crushed acorns are favorite foods.
Oaks
have without a doubt caused an increase in the number of species of plants and
animals in the towns of West Texas. This
review only skims the surface of the changes.
Keep your eyes open!
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