POTENTIAL CULPRITS: WOODPECKERS OR CARPENTER BEES?

(Ed.'s Note: Well, we asked. When a friend of this blog noticed that his century plant (desert agave) had a perfectly round hole bored into its trunk, he asked if we could inquire from our three readers if anyone knew what animal, bird or insect might be responsible. We received several, including one that said woodpeckers might be the culprits. That may be. But this explanation submitted by one of our readers is an intriguing, if not plausible explanation. We had no idea we had carpenter bees in town, although it wouldn't surprise us since we even have Africanized bees and a few species of the homespun variety. We don't know if our friend will venture to peek into the hole to see if it's bees or woodpeckers, but it remains an intriguing look into the symbiotic relationship between local plants and local fauna. We thank lilaknight for this info.)  

By West Virginia
University Extension Service.

"Spring is the season when homeowners begin to notice large round holes in their wooden porch trim. The same people just might happen to mention being dive-bombed by a large bumble bee.
These two seemingly unrelated events can mean only one thing: carpenter bees.
Identification
The common carpenter bee in West Virginia (and South Texas?), Xylocopa virginica, does look like a large bumble bee. Like bumble bees, carpenter bees are black and yellow and about 1 inch in length. If you get close enough, you can tell the two apart by looking at their abdomens. The abdomen of a bumble bee is fuzzy, while the carpenter bee’s is shiny black and hairless.
Male carpenter bees often exhibit defensive behavior by flying around the heads of people who approach their nests. Male bees have no stinger and are harmless. Although female carpenter bees Have stingers, they are usually only seen flying in and out of nest holes, paying no attention at all to people, and having no desire whatsoever to sting anyone.
Biology and Habits
Carpenter bees are solitary bees, unlike bumble bees which live in colonies underground. Carpenter bees often return to same nest site each year. They typically nest in softwoods like pine. Carpenter bee entrance holes are almost perfectly round and 1/2-inch in diameter. Carpenter bees do not eat wood but only nest in it, feeding instead on pollen and nectar. They usually build their nests only in horizontal wood members, such as roof trim, siding, steps, decks, and porch railings. Nesting by a single pair of carpenter bees will normally cause only cosmetic damage to wood.

Adult carpenter bees spend the winter in their tunnels. They emerge and mate in the Spring. After mating, the female bee starts a nest brood tunnel in which to lay her eggs.  She may use the same tunnel that she emerged from, with or without enlarging it, or bore a new one. If she starts a new tunnel, she begins by using her jaws to bore against the grain of the wood. She tunnels to a depth of about an inch before turning at a
right angle and continuing with the wood grain. 

She hollows out the tunnel with her mandibles, at a rate of about 1 inch per week. Average gallery length is 4 to 6 inches, but up to 10 feet is possible in galleries used by several bees."
However, there are other commenters who feel strongly that it is the work of a woodpecker that did this, indicating the size of the bored hole and the relatively small size of the bees.
One wrote: A Golden-fronted Woodpecker made that hole, likely last spring and probably used it as a nesting site unless something disturbed it before it was completed and it abandoned the nest. This is the most common of the woodpeckers in our area. If a woodpecker isn't using it other cavity nesting birds like wrens and titmice and even parrots and parakeets may move in next spring or a Screech Owl may use it as a day roost any time. A clue that parrots or parakeets are using the place as a nest is that that nice round entrance hole will often be enlarged and it will be irregular and ragged in shape. Parrots are not the squared away carpenters that woodpeckers (carpinteros) are."
This writer's opinion is also supported by some literature put out by http://identify.whatbird.com/obj/850/_/golden-fronted_woodpecker.aspx"The Golden-fronted Woodpecker is generally located in North America. It resides in multiple woodlands throughout Texas and Oklahoma, and is especially rampant in the lower Rio Grande Valley, Texas. Nests are drilled out of trees, which are later reused by other species of birds. Taller varieties of pecan, oak and mesquite are the preferred materials for nests. In urbanized areas, they may also use telephone poles, fence posts and man-made bird boxes. The Golden-fronted Woodpecker primarily eats insects and vegetation. Their favorite food is grasshoppers, but they also dine on beetles and ants. The conservation rating of the Golden-fronted Woodpecker is Least Concern."
(In the picture at right, the woodpecker is fighting it out with white-fronted parrots for the same hole.

The carpenter bee theory seems to be borne out by this selection from the http://eduscapes.com/nature/notcacti/index1.htm where it states that: "The century plant, also called desert agave, spends most of its life as a rosette, a cluster of basal leaves. Characteristic of other agaves, its flowering is delayed. But in this case, it could be as long as thirty years – but not even close to its erroneously labeled century. 

When it does flower, the stalk erupts from the center of the rosette and grows at an astonishing rate, two and one-half inches each day, until it reaches five to fifteen feet in height. The plant then blooms for several weeks and then dies. The plant's death is largely due to expending its supply of water and plant food resources to grow the flower stalk. 

Therefore it has to die, but not before its flowers have been pollinated and up to 65,000 seeds have been propagated.  Carpenter Bees are a rather large Bee. They bore holes into soft wood to lay their eggs. They do not eat the wood, however they will cause some damage to the wood as they excavate their holes.
The century plant is an enormous food and water source for desert life. During the driest months of the year, its leaves are often the only water source for many bighorn sheep. The yellow flowers that bloom May to July when few other plants flower provide nectar for hummingbirds and insects. The plant provides food for the caterpillar of giant skipper butterfly, and carpenter bees make their home by tunneling into the pithy flower stalk."
Like we said at the beginning, we asked. We'll just have to ask our friend to keep an eye on the agave and see is he can solve out mystery.