Category: catclaw acacia

Rare Autumn Color Transforms the San Pedro’s Forest

For the past three years in a row, I had made a date with the San Pedro River: I would spend my birthday walking the river under the gilded magnificence of tall willows and stately cottonwoods alight with prime autumn color. For the past three years, the autumn colors have failed to shine. “Autumn,” if you can call it that, comes late to this river’s riparian forest. Fall colors do not peak here until the second week of December. The timing does not vary due to temperature or climate, it functions via the most universal and reliable of nature’s temperate region chronometers: the photoperiod. In most years, the trees along the river either suffer a hard freeze before the second week of December, or they get stripped off by strong winds, or both. Freezes can rob the forest of its fall color overnight by turning all of the leaves a withered brown. 

When conditions are just right, chlorophyll fades from the leaves to reveal anthocyanic compounds that transform the forest canopy into a fluttering galaxy of bright yellow leaves. This year brought a reprieve from late November winds and early December freezes – this was one of those special years…so I set out for a walk on my birthday, a serene journey into the river forest. The following images help to tell the story of a rare day on the river.

The  first place I walked to that morning was a hilltop where I saw the lone cottonwoods pictured above, lifting plumes of sunlit gold skyward. As I watched, a great egret came sailing out from behind the trees! Imagine an elegant pair of outstretched wings spanning over four feet, the bird flawless, brilliant snow-white, set against a clear blue sky. My wonderful new binoculars brought this seldom seen creature in close and sharp – what a gift it was to witness the egret! My jaw went slack when a second egret appeared to join the first. The pair then departed northward, winging over the tops of the trees as they followed the river that sheltered and fed them. I envied their freedoms.

A rich blend of plant communities (and thus many habitat types) is underscored by the blaze of autumn color along the river. Here, a dense growth of velvet mesquite and catclaw acacia flank the riparian forest. Highlands are visible in the distance, providing more habitats for wildlife and wild plants that vary according to aspect and elevation.

I left the hilltop, then returned to the riparian forest, where I walked down to a favorite sitting spot by a bend in the stream just below a vertical cutbank. There, a set of cougar tracks was pressed into  the moist sand, made the night prior by an adult male. I sat under a willow to look, to watch, and to take in the morning’s biophony. The forest was quiet, the still air punctuated by a slight rustling of leaves above, the quiet murmur of the river water, and the voices of a few birds. As sunlight warmed the cool air, small clouds of midges began to rise within discreet, sunlit areas above the water. There, the air temperature was most favorable for their airborne gatherings. As the midges danced in the light, a gray flycatcher began sallying back and forth into the insect clouds, garnering breakfast with typically adroit flycatcher movements. Then another bird joined in the feast, flying into the swirling insects to garb morsel after morsel with some amazing acrobatics. It turned out to be a ruby-crowned kinglet! I had no that clue kinglets could – or would – engage in such feeding behavior.

A favorite and long-familiar reach of the San Pedro River in mid-December dress.

Next, I walked down the river until I got near the northern terminus of my trail. The going was easy, the stream shallow in most reaches. I was glad to find no recent signs of trespass cattle anywhere, nor any signs of feral pigs. There was little in the way of animal tracks, as a heavy mantle of recently shed leaves covered most of the ground thoroughly.

A dense carpet of crisp, shed leaves draped the forest floor. This made for noisy walking!

I heard these Gould’s turkeys before I saw them emerge from the forest to slake their thirst at river’s edge.

Gooding’s willows cast long shadows into a beguiling artist’s chiaroscuro of glistening water, dappled light, and autumn leaves.

As I neared the end of my walk, I veered into the forest to avoid some deep water. (For much of the way, I’d been wading.) The wind suddenly arrived, causing a blizzard of shimmering golden leaves to return to the ground that had bore them, an entrancing display of fluttering motion and light as one of nature’s grand cyclic acts of life unfolded all around me.

Truly a stellar birthday!

An Inferno of a Summer, Huge Arthropods, and Arizona’s Tiniest Mammals

This has been one of the driest and hottest summers I can recall here in the Middle San Pedro River Valley. During “normal” summers, monsoon rains arrive between the middle and the end of June and continue through August and much of September. The two previous monsoon seasons brought us a welcome abundance of rain, but this year has remained very, very dry. Daytime highs for the past six weeks have averaged around 106°F., with more than a few days reaching 110° or higher. This year’s highest temperature registered at a crispy 115°F. on July 17.

Our mesquite bosque remains dry, the understory of dense London rocket plants yellowed and brittle. Usually, by the end of July, this scene should be bursting with vivid green growth in the form of Amaranthus palmeri and many other native plant species.

Despite our xeric summer, velvet mesquite trees in our bosque have produced a nice crop of pods, followed by a second flowering during the past couple of weeks. The trees are drawing on water from last summer’s abundant storms; mesquite has the rare ability to transport water in both directions within its extensive, very deep root system. Water can be transported deep underground and stored for later use.
A fresh splay of velvet mesquite blossoms perfumes the air and reminds us that desert plants have evolved uncanny mechanisms to stay alive and even thrive under dry, difficult conditions.

Mesquite blossoms lead to garlands of bright green pods growing from pendant branches. Mule and whitetailed deer love to feed on low-hanging bunches of these young pods. When ripe, the seed pods turn yellow and fall to the ground. There, they become one of the most crucial and nutritious wildlife foods in the entire ecosystem, eagerly fed upon by a very long list of native animals from mice to coyotes to bears and many more.

Despite the drought, this was a banner year for a widespread local species known as catclaw acacia, Acacia gregii. (See the photos in my previous blog post.) Throughout the valley, these large shrubs/small trees flowered explosively. The scent from their blossoms is intoxicatingly wonderful. Much like mesquite pods, the seed pods of acacias are fed upon by a wide variety of native wildlife.

Dry conditions leave fine coatings of dust on our driveway – an excellent newspaper that I strive to read daily. This summer has revealed tracks of mice, kangaroo rats, gray foxes, coyotes, raccoons, mule and whitetailed deer, a cougar, hooded skunks, quail, doves, and other birds including this trackway of a Chihuahuan raven.

A closer look at the raven’s tracks reveals their relatively large size, distinctively lobed feet, and shallow drag marks made by their posterior claws.

A mystery…last week, I noticed something I had not seen before: dense clumps of small, black native bees forming in certain graythorn (Zizyphus) bushes. I have no idea what is going on here, nor what species these bees are – there are well over 1,200 species of native bees in this ecosystem, representing the richest known bee fauna in the world.
I found this adult giant mesquite bug (Thasus californicus) roaming under my ramada the day before I posted this blog. These are large insects that are true bugs (Hemipterans) as opposed to a type of beetle (Coleopterans).

A lateral view of the mesquite bug reveals the tube-like mouthpart that it uses to feed on plant liquids. The tube is inserted, syringe-like, into the stems of plants. These specialized feeding tubes are a primary characteristic that separates true bugs from beetles.

Prior to maturation, giant mesquite bugs exist in the form of wingless nymphs. The nymphs form colonies that feed on liquids from various species of trees and shrubs. The nymphs go through several instars before finally transforming into adults, all of which exhibit these very bright red colors. The nymphs are protected with self-manufactured noxious chemicals that make them taste bad to predators, hence their aposematic coloration.

Arizona’s smallest mammals are shrews; I found this one – dead but still warm – on the floor of our bosque. This species is known as the desert shrew, Notiosorex crawfordi. Shrews are among the most highly energized, frenetic mammals on Earth. They require remarkable amounts of food – up to nearly half their body weight on a daily basis. They almost never stop moving, constantly on the hunt. I wonder how they have time to dream.

This sight greeted me a few mornings ago, when I walked outside just after dawn to see this giant centipede (Scolopendra heros) clinging to the wall of my adobe building. The broom handle gives a sense of scale. This one was just under seven inches long – and they get bigger than this, up to nine inches in length. Very large specimens measure around an inch in width across their backs, are equipped with formidable pincers, and can move at astounding speeds.

High winds snapped this velvet mesquite trunk at the location of a cavity hollowed out by Gila woodpeckers. I have seen such tree breaks many times, both locally in this southern desert and in the northern Rockies. There is a complex relationship between cavity-making birds and their varied roles in forest ecology that may be more important we know.

A close look at the exposed woodpecker cavity shows the remnants of a successful nesting season. Last month, a pair of ash-throated flycatchers raised a batch of young within the sheltered confines of this tree cavity.

This image should be entitled “HOPE”… a series of empty, dry water buckets under my roofline, hoping and waiting for the summer rains. Why collect rainwater when we have a well, particularly summer rain water? The summer storms often feature stunning amounts of lightning, which allows substantial amounts of elemental nitrogen to be carried from the atmosphere (via rainfall) down to the ground, where it greens the Earth. All gardeners should learn that summer rain water collected after lightning storms works magic on plant growth.

A Spectacular Bloom Year for a Magnificent Desert Plant 

(Click on the blog title above to be directed to my blog site for a better experience and a chance to see the featured image, which is deleted from the email versions of this blog.)

Soaptree yucca (Yucca elata) is one of the crown jewels of the Chihuahuan Desert Ecoregion – a tall, stately, easily recognized species that is common in the Middle San Pedro Valley. Its distinctive plume of beautiful white flowers can be seen by the naked eye at distances upwards of a mile away. Soaptree plants can live for more than three decades and attain heights exceeding 15 feet. This is one of the few tall flowering plants in North American deserts that does not strike up a relationship with high-altitude pollinators like birds, bats, hawk moths, or bees. Soaptrees, like many other yuccas native to the West, are pollinated exclusively by only a few genera of specialized, small moths: particularly by insects known as yucca moths, (Tegeticula yuccasela or T. maculata).

The striking white plumes of soaptree yucca flower heads can be seen in great numbers this year, a special early-summer sight that part-time (winter) residents of southern Arizona may never experience.

The most common height of local soaptrees varies between 7-10 feet, but ancient grandmother plants like these can top 15 feet or more in stature.

Large, gorgeous plumes of very soft-textured, delicate, bell-shaped flowers adorn blooming soaptree yuccas.

The close relationship that this yucca has with its pollinating moths has been going on for millennia. The moths are white in color and rather small, with wingspans around an inch in width. After mating, yucca moths fly to the flowers, where they gather pollen. The pollen is carefully packed into specialized depressions on the surface of the flower ovaries. Without this stimulus, the yuccas cannot produce seeds. In return, the moths’ larvae feed on yucca seeds in the developing seed capsules.

A closer look at the flowers, whose futures depend upon an inconspicuous but crucially important moth.

This yucca is among the few desert plants that can thrive in a sand dune environment, but they do very well in other habitats as well, such as the lower elevation uplands in this valley. Unlike other yuccas, Yucca elata forms vertical rhizomes that plunge downward to depths of five feet, then grow out laterally to sprout new plants. Plant rhizomes usually grow horizontally, but this yucca’s departure from that rule enables the plants to do well in hot, dry environs.

Yuccas have a myriad of ethnobotanical aspects, for they were put to many uses by most, if not all native tribes living within the range of these pants. Yucca roots are rich in saponins, which were extracted to make effective soaps and shampoos. Many parts of the pants were consumed as food, including the flower buds, fresh flowers (eaten raw or cooked), and the flower stalks. Tough fibers from the long, linear leaves were cleverly utilized to make twine, rope, footwear, and textiles.

It has been a banner year not only for our local soaptree yuccas, but also for catclaw acacia, Acacia gregii. This specimen hosts a galaxy of highly fragrant yellow flowers whose enchanting scent forms a delightful olfactory signature characterizing the last week of May in the Middle San Pedro Valley.

full bloom alongside the catclaw plants are white-thorn acacias, Acacia constricta. The spherical, bright orange flowers exude a sweet fragrance that compliments their neighbors’ perfumes.

A Landscape in Bloom as Young Ravens Explore Their New World

May is such a beautiful month in the Middle San Pedro Valley! Our mesquite bosque bursts into new life, sprouting a light-filtering canopy of spring-green leaves. Birds are singing from the trees, building nests, and rearing their young. Lizards are a near-constant sight and snakes have been leaving their telltale trackways in the dust. Late in the month, something special happens as catclaw acacias suddenly explode with constellations of pale yellow blossoms, perfuming the valley with their luscious, signature scent. The heat of summer begins to blanket the land in newfound warmth, gearing up toward the frying-pan month of June.

This has been a banner year for catclaw acacia, Acacia gregii. The bushes (at times, these plants grow into small trees) have literally colored parts of the valley floor with an unusually dense show of blossoms. This is one of the desert’s special plants that begs to be appreciated in an olfactory way…push your nose up against any fresh flower, and one whiff of its sweet, heady perfume will weld the current zeitgeist of this wonderful region into your permanent memory.

A dense stand of palo verde (Cercidium spp.) in full bloom colors an entire ridge with literally millions of flowers, all set beneath tall saguaros that are also in bloom. Palo verde and saguaro are two flagship plants of the Sonoran Desert Ecoregion, here reaching its southernmost boundary in the valley along this very ridge. The spot that I stood on to gather this image marks the northernmost extension of the Chihuahuan Desert Ecoregion. Two great ecoregions merge here, enhancing the rich biotic diversity that is so much an intrinsic part of the San Pedro River Drainage.

Most of the early wildflowers are gone by this month, but some wait for their bloom times, like this display of cow pen daisies, Verbesina encelioides.

A closer look at the vivid yellow flowers of cow pen daisies. The yellow “petals” are actually sepals – subtending the many dozens of tiny individual flowers that crowd the centers of these composite blooms.

I am happy to report that our resident Chihuahuan ravens have successfully fledged a trio of youngsters this year. This comes in welcome contrast to last year’s double brood failure; their initial brood was decimated by hungry coyotes on the first night that they spent out of the nest, and the second brood (rare in ravens) was lost to raptors.

Mavis skillfully positions a bulky chicken egg in her beak and readies herself for takeoff. The youngsters must be fed very frequently. Ravens are experts at finding the eggs of other birds. Mike and Mavis never hesitate when we leave an egg on the ground for them.

Loud cries emanating from the raven nest less than 120 feet from my desk window have been a daily part of this month’s panoply of happenings in the natural world. Young ravens have zero shyness when it comes to screaming at their parents for more food, more food, more food! Five days ago, they left the nest to begin exploring the outside world. We see and hear them many times a day as they roam with their parents and learn the complex magic of raven flight mastery. Few North American birds attain a higher level of flight skills than ravens do.

The three youngsters at rest in the mesquite trees only days after fledging. This is a vulnerable and crucial time for the young wolf birds. They must sharpen their flight skills quickly, for predators lurk above and below. It is also the one time in their lives when learning is greatly accelerated as they stay with their parents for weeks, who guard and teach their brood with steadfast devotion.

Raucous cries and characteristic fluttering wings are a part of every feeding, as Mavis approaches one of her ever-hungry youngsters with a crop full of food.

This has been a sad year for migrant birds, with fewer numbers and fewer species than usual, but there are still plenty of feathered creatures bringing life and – at times – utterly dazzling colors to our world. This male broad-billed hummingbird could not possibly have been dubbed with a duller nor less imaginative name.

Among the resident bird species that are still doing well are lesser goldfinches, which crowd our seed bags daily, enriching our surroundings with cheerful choruses of bird song.

During every summer, wet mud or other moist places on the ground attract large congregations of gorgeous, diminutive butterflies. “Blues” as they are collectively called, belong the the lepidopteran subfamily Polyommatinae. Approximately twenty species occur in Arizona. The moniker “blue” comes to light any time these insects open their wings, revealing brilliant blue coloring on their upper wing surfaces. The species pictured is known as the marine blue, Leptotes marina.

Only male “blues” congregate at puddles or on moist soil and animal scats. The males may require certain minerals, amino acids, and/or salts that the females do not. Local native host plants (for their larvae) include saltbush, catclaw acacia and velvet mesquite. Each species has its own hibernation strategy, with some overwintering as either eggs or larvae, as opposed to the far more common lepidopteran chrysalis. Other species  have close associations with ant colonies – such as larvae pupating inside ant colonies, or larvae being tended and protected by ants as they feed on their host plants.

Warm morning light dapples the coat of this mature mule deer doe as she slakes her thirst at our “bird pond.”