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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.
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.”
Behold the common poorwill, the only bird on Earth known to hibernate! My first acquaintance with this fascinating creature happened in the late ‘80s. At the time, I was living in an old log cabin nestled into the stony folds of Montana’s Rocky Mountain Front. There, I heard an unmistakable signature call lilting out of dusk-wrapped foothills on warm summer nights, a plaintive two-note call that to some, sounds like “poor – will.”
Summer after summer, I heard their voices – sometimes I would glimpse one in flight. Much about poorwills remained a mystery to me, until one fateful evening. As I was driving up a dirt road, a small bird abruptly rose up in front of my pickup truck. The resulting collision was unavoidable. I stopped immediately, dismayed to find an inanimate lump of feathers caught in the grill. Gently, I extricated the bird and gazed at its limp form in wonder; cupped in one hand, its warm feathers felt gossamer-soft. My attention was immediately drawn to its head, quite large relative to the rest of the body. Two huge, liquid eyes characterized the bird’s visage. What looked like a ridiculously tiny beak barely poked out from a covering of feathers. The area around the beak (and the rest of the bird’s hidden mouth) was festooned with a fringe of curved, jet black, semi-rigid bristles.
Now it gets even weirder. I had read up on these birds, so I knew that they were grouped in a strange family known by several names: frogmouths, nightjars, or goatsuckers. (Yes, goatsuckers, but that is another story altogether.) Curious, (as any naturalist should be) I pried the beak apart. My jaw fell in synchrony with the yawning beak, for the beak did not merely open; the bird’s head nearly split in two! The hidden edges of the beak extended far back to form an absolute cave of a mouth, a great, gaping maw that could make any shark jealous. Why such a mega-mouth, and what was with those bizarre bristles?
Poorwills are highly specialized to feed on flying insects in low-light conditions. Having a wide gullet for a mouth makes it much easier to catch insects on the wing. Their heads are unusually large because plenty of room is needed to house the mouth and a pair of very large eye orbits. Big eyes gather more light, handy for spotting prey in the dark.
Here at the interface of the Sonoran and Chihuahuan Deserts, habitat like this is well suited for poorwills. A scattering of low shrubs, cacti, and plenty of open ground in between provides these amazing birds with unobstructed views and open flight paths to help them catch flying insects.
Some ornithologists speculate that the stiff bristles form a sort of tactile net around the mouth, effectively enlarging the bird’s open mouth. This increases a poorwill’s chances of success when chasing its evasive flying food. During the heat of summer, these desert-dwelling birds reveal another advantage enabled by their gigantic oral cavities. As they roost during hot days, poorwills open their mouths while fluttering the muscles in their throats, cooling themselves in a manner similar to a panting dog. The efficiency of such a cooling method is substantially amplified due to the large surface area of the bird’s mouth.
A close look at a poorwill’s head reveals the long rictal bristles that fringe their mouths.
So what about poorwills and hibernation? Here, in the Sonoran and Chihuahuan Deserts, poorwills crawl into rock crevices where they go into a state of hibernation or extended torpor (these terms remain somewhat ambiguous) for months during the winter. Their respiratory rate and heartbeat drops substantially, while their body temperature plummets to nearly 40° F.! An astute scientist is credited with “discovering” that poorwills hibernate as he conducted research on them in 1948. However, indigenous peoples knew this long before 1948. For example, the Hopi Indian word for poorwill is (roughly) hölchoko, translated as “the sleeping one.” Thus, much like Columbus, the 1948 discovery simply revealed knowledge to a different culture, knowledge that was already known to another. (With respect to Christopher Columbus, it is impossible to “discover” a place where people already live. A combination of cultural condescension and arrogance can imprint our history books with less than the truth.)
There is much more about poorwills that makes them such captivating, beguiling birds. Their camouflage is utterly incredible. Poorwills roost on the ground where they literally merge with their surroundings. The cryptic patterning of their plumage renders them extremely difficult to spot. On more than one occasion, I have nearly stepped on them before they revealed themselves through movement. The genus name for poorwills is Phalaenoptilus, ancient Greek for “moth plumage.” (Our birds are a very unique species, for no other bird on the planet shares their genus epithet.) The scientific name Phalaenoptilus is fitting in two ways, for many moths are extremely well camouflaged, and moths make up a large part of a poorwill’s diet.
Don’t let the red eyes fool you! This is an artifact of the light projected by a camera flash. When seen in natural light, the eyes of poorwills are very deep brown or black in color. Read the following paragraph for more details.
Like other members of their family, poorwills possess a special layer of cells at the back of their huge eyes known as the tapetum lucidum, rarely found in other birds. These cells allow them to see much better in low-light conditions. As for the glowing red eye in the photographs, that results from light reflected from the choroid, a thin layer of connective tissue surrounding the outer periphery of the eye. The choroid is nourished by a rich supply of capillary blood vessels, hence the red color. (The “red eye effect” sometimes seen in photographs of people is caused by similar choroid reflectivity.)
Weird enough? Not quite. On the Montana evening when I held the unfortunate poorwill in my hand, I had missed something: the bird’s feet. Poorwills possess pectinated claws (one per foot) with comb-like, serrated ridges that are used to preen plumage and to rearrange the rictal bristles. There is also the fact that these birds do not build nests – they simply lay their whitish, non-camouflaged eggs on the open ground. How they manage to keep their species alive via such seemingly risky egg-laying habits may seem enigmatic, but it works, for there are poorwills year after year. Here in the uplands and mesquite bosques of the San Pedro River Valley, their lonely calls are an intrinsic part of the desert’s twilight world.
Finally, a note on the poorwill images: they were photographed recently here in Cochise County, AZ, then generously supplied by a friend for use in this blog. Unless otherwise noted, all other photographs posted on this site are original copyrighted images by the author.
