Who made a saguaro hole in one?

Out in the desert, you may hear a loud “Chirrr” sound. Look up, and you may see a flash of black and white wings, then see a brown-headed individual running or hopping up the trunk of a tree, if there are any trees around, or a cactus. If it’s a cactus, that’s got to be a fairly death-defying move, navigating among the thorns.

When you see all of these clues together in southern Arizona or northwestern Mexico, it’s quite likely you have spotted a Gila Woodpecker.

You can recognise Gila Woodpeckers, Melanerpes uropygialis, both male and female birds, from the thin vivid black and white bars across their wings and back, and their brown heads. In addition, the male has a red patch on his forehead. And, as well as their distinctive “Chirrr” call, they also make loud peeps.

In an unusual and clever tactic, they use their tails to prop them up vertically as they locomote, hunting for insect meals on bark or cactus skin, or when they hammer out nests.

The big black holes you see in the sides of many saguaros? Credit goes to these folks!

They use their strong beaks on their well-cushioned heads to whack nest holes into the sides of saguaro cacti, and if they can find any, other tall woody plants of the desert, including cottonwoods.

The nest holes they excavate in saguaros, which are often used by other birds, eventually harden into “saguaro boots.” These woody, rounded, boot-shaped forms remain even after the saguaro dies, and have been used as containers by humans since the olden days.

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Who’s standing tall and alone?

A striking sight in the Sonoran desert is a lone saguaro cactus.

Saguaros (Carnegiea gigantea) provide food and shelter to a surprising number of creatures. This includes humans, who harvest their fruit, and use their skeletons for fences and construction.

These cacti have an amazing variety of adaptations to the desert.

First, check out the color of the stems, a pale green, indicating they contain chlorophyll. Since saguaros do not really have leaves, the stems have to do the work of photosynthesizing and producing food. The pale color keeps the plants from absorbing too much hot sunlight and getting burned.

If you look closely, you will see lines of defensive thorns on vertical accordion ridges. The whole plant can expand to hold more water after a good rain, then accordion back in as it uses the water

What you can’t see is the root structure. Instead of sending down a big tap root, like many plants, they send out numerous very long horizontal roots near the surface, to better gather any moisture nearby.

That’s why they’re lonesome looking—they need to grow far apart. And that’s why, in the old days before we realized it was unethical, (now it’s also illegal) people would dig them up in the desert, transplant them, and they would die, because the majority of  the root structure was left behind.

Wildlife Rescue Open House

If you are near the Phoenix, Arizona area next weekend, you have an opportunity to meet and learn about some of the cool creatures of the hot desert.

The open house is on November 21 and 22, 2015, at the Adobe Mountain Wildlife Center.

www.azwildlifecenter.net/events.asp

Because this is a wildlife rescue station, the population changes all the time. Depending on who is recovering there, you may see eagles, desert tortoises, bobcats, falcons, or ringtails.

Or maybe even the creative and industrious packrat!

Desert clouds

The desert can produce some of the most amazing clouds.

Like this:

Ocotillos and visitors

So, the original idea here was to talk about how Ocotillo plants (Fouquieria splendens) in bloom seem to host bird or pollinator visitors at almost any time of day.

It seemed like a good idea to do at least one random sample of observation before declaring this.

And sure enough, during a 3 minute segment one spring afternoon, a few days into full bloom for the ocotillo, there were two bird visitors and several pollinator insects. Now this was just one casual observation, but it indicates how often you see creatures near or on these plants.

As noted in an earlier post, Verdins, (Auriparus flaviceps) the very small birds with yellow heads, are frequent visitors, apparently looking for insects. Finches are also common. And hummingbirds can be seen throughout the year.

It is amazing that any birds can find a firm foothold on the thorny stems. Clever feet.

Remember that the ocotillo is not a cactus, although it may look like one during some parts of the year. It’s in a completely different group. In fact, for most of the year, it looks like a bundle of dead sticks, and if you first saw one for sale in a garden center, you might wonder what they were trying to sell.

One example of right now…

…and right next to you, in the North American Sonoran Desert–quite a variety of flowers along the side of the Phoenix-Las Vegas highway, south of Wickenburg, on March 12: globe mallow, desert lupine, creosote bush, brittle bush, and many others. Amazing that there are so many natives right along the verge.

Again, lower elevations, farther south, means earlier flowering time.

Interesting to watch the populations change even with slight elevation changes, going up and down hills.

Look for places that have not been bulldozed or grazed, so there are fewer weeds and more natives.

Wetlands, swales, ditches, creeks, or washes may have unusual species.

This is prime time for flowers. They change so quickly, it’s worth looking as often as you can.

Too Wet!

A surprising limiting factor in some parts of the desert is too much moisture.

Wait, you say, I thought deserts were too dry?

Because there’s usually so little rain, nobody is really prepared for much. So even what might be considered a light rain elsewhere can be enough to flood out desert burrows, nests, hollows, and lowlands. If you are a creature who can move fast, or a plant that can hold its breath, you will get through it.

But even in the desert, rain is not always light. During the summer monsoon months, and a few other times of year, there can be heavy downpours.

And adding to the effect, there’s that old caliche we talked about before. This is the impervious layer of minerals and clay that forms over time a short distance down under the desert surface, and acts as a water-trap. The water can’t sink in–so where it can, it slides off downhill.

With a light rain, you can suddenly get a flash flood. With a heavy, or extended rain, you can get massive dangerous flooding, the kind that kills animals, large as well as small, and washes away trees and cars and buildings.

In the middle of many human habitations in the desert, you will find long empty wild spaces, often called “washes.” These are where the flash floods wash through, carrying away whatever is in their path.

It’s strange, when you think about it, how moisture could be a problem, and a limiting factor, in both directions in the desert.

Or maybe not. Because a lot of living things want conditions that are not too much, or too little. Instead, they want things to be generally within an agreeable range. So when you look at a limiting factor, it can be fun to check if there is another one lurking at the opposite side. Yet another mystery.

Who lives in this cactus?

Who you find living in any particular cactus will depend on when you look.

Many of the large holes in saguaros are originally drilled (although the process sounds more like a jack hammer than a drill) by Gila woodpeckers, who peck into the cactus to hollow out an area for a nest.

One interesting result is that the cactus, always fearful of losing moisture, forms dense scar tissue around the excavated area. This means that when the cactus dies and the flesh falls away, what’s left is the interesting lattice of cactus skeleton, plus an occasional hard rounded shape that looks something like a boot—so it is called a cactus boot. Native people gathered them and used them as containers for liquids.

Back to the cactus-dwellers. While the plant is still alive, these nests drilled inside saguaro cacti are prime real estate, the perfect place to find thorn-protected shelter until the kids grow up and fly away. At first, after the cactus heals and get less gooey, the  Gila Woodpeckers or related birds who excavated the nest holes get first dibs. But later years may bring entirely new sets of residents.

Adiabatic—a what?

If you listen to the explanations given by weather forecasters, you may have heard the word adiabatic.

No, it’s not a disease related to blood sugat—that has a BET in the middle, not a BAT.

Instead, it is one very cool reason that storms suddenly pop up out of a clear sky in the desert.

Adiabatic cooling or warming happens when the pressure on a blob of air increases or decreases. When desert air hits a mountainside and rushes up the mountain, the air expands, gets “thinner” and cools as it rises to a higher elevation.

This means that if there is any moisture in the air, there is less energy to keep it suspended, so the moisture is more likely to condense, and form rain.

The opposite happens when air flows downslope—it warms as the pressure increases because the molecules are closer together and bump into each other more.

Maybe that is one reason that places east of mountains in North America are often more warm and dry than places to the west of mountains. Not only does the moisture get wrung out of the air on the western upslope, even very wet air from the ocean, but following that, some of the moisture on the downslope gets absorbed back into the falling, compressing, warming air.

Cool!

Or rather, cool, then warmer and drier!

 

New Desert Creatures Mysteries e-book

Now you can get a great Desert Creatures Mysteries e-book.

It goes into detail about the strange animals of the desert, and some of the cool science about them.

https://www.smashwords.com/books/view/455225