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.
For the past twenty years or so, I have participated in a coordinated volunteer project aimed at monitoring the presence of water along the length of the San Pedro River in southeastern Arizona. Organized by The Nature Conservancy, this project provides important data to scientists, land managers, and many others on the health of the river system during the hottest and driest month of the year. The data is collected the old-fashioned way – gathered by teams who experience the river in the best and most intimate manner possible, by walking and wading. Every June, I collect a portion of this data along a rare, perennially-flowing reach of the San Pedro located in the river’s middle valley, often accompanied by friends and neighbors. This year, two wonderful friends who also happen to be great neighbors assisted me in this worthwhile and delightful task.
Since June always brings oven-like temperatures, we began walking around 5:30am along a waterless stretch of the riverbed. Almost immediately, we discovered fresh tracks of an adult black bear and a cougar, etched in dry sand. One and a half miles in, the magic of water appeared. From that point on, the river flowed steadily. Because the brush is often nearly impenetrable along portions of the riverbanks, we waded, a much easier way to travel as long as one can avoid hidden lenses of quicksand. More mammal signs and tracks appeared; Coue’s whitetail deer, mule deer, javelina, coyote, bobcat, raccoon, coati, skunks, cottontail rabbits, mice and rock squirrels. Familiar bird songs spilled from the forest; summer tanagers and kingbirds, ash-throated flycatchers and song sparrows, southwestern willow flycatchers and black phoebes, grey hawks, tyrannulets, northern cardinals, Lucy’s and yellow warblers, and more.
The river in June is a different world from the surrounding vastness of desert habitat types – humid, verdant with profuse life, cool and shaded. It feels and smells almost subtropical. So much life graces the river and its forests in June that these annual walks have become my favorite time to explore and experience the beauty of the San Pedro.
Wading this desert river in the heat of June is magical. The cottonwood-willow forest stands tall and green, casting shade and coolness enabled by millions of fluttering leaves. The forest’s understory is verdant with lush growth. Eight-foot tall burr reed (genus Scirpus) plants crowd the riverbanks. Aquatic patches of speedwell (genus Veronica) glitter with multitudes of blue-purple blossoms. Tall willows form a vivid green arch overhanging the river. Birds sing from the depths of the forest, many butterflies, bees, and wasps drink from water’s edge, and scores of lowland leopard frogs leap at one’s every step. Below the surface, schools of long-finned dace are darting like shafts of animated light through the clear water. The continued presence of native frogs and fish are strong, positive indicators of the health of this aquatic ecosystem.
Among the most remarkable predators in the insect world, dragonflies are a common sight along the summer river. Some twenty-two years ago, an entomologist discovered nearly one dozen species of dragonflies and damsel flies that were new to science along this part of the river.
We waded for a couple of miles, feeling the warm, shallow waters of the river filling our shoes, until the waterway started to broaden and slowly deepen. I suspected a beaver dam was ahead. We climbed up on shore, then began to weave our way through a dense tangle of tamarisk and seep willow. Before long, we could see the beaver pond clearly, the water deeper and deeper, then the dam, plugging the river with a meter-tall, thirty-foot span of branches, twigs, tree limbs, rocks, and mud. I was elated to see that this reach of the river had beaver activity once again. The ecological and hydrologic benefits of beavers to this river – and many other waterways – are legion. I devoted an essay to this important topic in my book, The Life of the San Pedro River.
A cool, deep pond extends upstream of the beaver dam. Such dams hold more water within the river system, helping to recharge the aquifers that feed the river and its forest. The positive benefits of beaver ponds to plant life and many wildlife species could fill a book. Note the turbidity of the impounded water, a sign that the beaver(s) had been active there the night prior.
A moment of reflection seated atop the beaver dam before I was almost envenomated by a rattlesnake. Photo by Tom Talbott.
My companions and I slithered down the steep riverbank to begin wading the final stretch below the dam. We had taken just a few steps when one of my friends suddenly threw his arm around me and pulled me out of harm’s way. A 3-foot western diamondback rattlesnake, coiled too close for comfort along the edge of the river channel, erupted in a frenzy of rattling. The forward third of the reptile’s body was off the ground and formed into an s-curve as the snake’s glistening black tongue waved slowly, curled backwards over its snout. Fully cocked, primed, and quite willing to strike. My fresh shoe print was about 14 inches from the rattlesnake. Had I not been yanked so suddenly by my alert friend, this snake would have probably tagged me. I have never come so close, despite encountering hundreds of diamondbacks here over the course of the last two decades. This experience underscores a crucial rule that I try to teach to everyone that I take into the wilds here – you should watch where every footstep is headed during the warmer months in southern Arizona! Sometimes, that is easier said than done.
This is the snake that I stepped far too close to, coiled, rattling, and very ready to strike defensively. Note the recent injury on its back, something that may have amplified its angry mood. If I weighed in at less than a pound or two, and a huge, towering, 200-pound bipedal mammal threatened to step on me, I’d be in a biting mood too.
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.”
I have always looked forward to the month of April in southeastern Arizona, for it brings a great diversity and large numbers of migrant birds to the land – or does it? The first time that I birded the San Pedro River was in April of 1977. In a word, that was a stunning experience. The numbers of birds were incredible, as were the variety of species. Today, the story could hardly be more different.
Migrant songbirds (and other migratory species) have been steadily declining ever since Europeans began to populate the North American continent. The rate of decline was slow at first, but it has increased continually through the centuries. During the past several decades, declines in bird populations have become so severe that some birds have become extinct, while others are persisting by the thinnest of threads.
Here in the Middle San Pedro Valley, I have been participating in avian surveys and have been keeping detailed records of local bird life for 21 years. The data is disheartening, but this year has been the worst thus far. Numerous species that have appeared on schedule at our property every past April are simply not appearing. Many others are here in very low numbers. Sadly, close to 100% of these declines are attributable to mankind. Overpopulation, urban expansion, climate change, pesticides and herbicides, tremendous habitat losses, loose house cats, and more add up to a world that is becoming quieter and quieter every spring.
What is spring without bird song?
Other happenings in the natural world have been occurring as well, ones that are not disheartening. Lizards and snakes have awakened from their winter brumation to add their grace, color, and life to the land. A few days ago, a Sonoran gopher snake appeared a few feet from my doorway, followed by the year’s first diamondback rattlesnake and the emergence of Clark’s spiny lizards. Our resident ravens, Mike and Mavis, have successfully hatched yet another brood and are very busy keeping their youngsters well fed. A nice abundance of wildflowers is coloring the upland slopes.
The gopher snake mentioned above. We always welcome these harmless and beautiful reptiles. They play an effective role in controlling rodent populations.
This was a slender male, close to 3 1/2 feet in length. Sonoran gopher snakes can attain lengths approaching eight feet, making them one of the nation’s longest native ophidians.A closer look reveals the large, curved, robust rostral scale at the forward tip of the snake’s head. This kind of scalation evolved to shield and protect the heads of gopher snakes as they push their way through soil and pursue rodents deep into their burrows.
Every year in this valley seems to bring its own explosion of certain insects. Earlier this month, incredible numbers of crane flies could be seen. I recall walks where every step flushed 20 or more from the surface of the ground. Crane flies belong to the family Tipulidae, with over 15,000 species worldwide. They are a successful and adaptable group of insects, for their presence in the fossil record dates back over 70,000,000 million years.
A pair of crane flies, busy assuring that their kind has a future. These innocuous insects are sometimes called “mosquito hawks,” for the mistaken belief that they prey on mosquitoes. On a recent walk in the valley with a friend, we paused to admire this rare cristate saguaro, made even rarer by its unusual paired, symmetrical shape.
Incredibly, on the very same day, another friend was roaming the valley when he discovered this huge, cristate specimen. Photo by Gilbert Urias. April brings the return of turkey vultures. Here, one has landed to scrutinize one of our bird watering dishes. Among several unique aspects of these vultures is the fact that they have no syrinx – the organ that allows birds to vocalize. Turkey vultures can hiss by expelling air rapidly, but they cannot call to one another nor utter any sort of song.A close look at the vulture’s head reveals a large perforation in the bird’s beak. When viewed at just the right angle, one can see that the large hole goes all the way through the beak to the other side. Turkey vultures locate the majority of their food via a keen sense of smell, an unusual trait among most other birds. The perforated beak likely helps these birds to smell with great facility, channeling airflow into their nasal scent receptors. (The quality of this enlarged image is poor due to limits that my blog hosting service places on image resolution.)
Shallow watering dishes can do wonders for attracting bird life and many other desert animals as well.
A wonderful and always reassuring sight! The riparian forest that is so deeply important to the valley’s wildlife glows with a verdant spring canopy of cottonwood and willow leaves. The color contrast between the riverside forest and the surrounding uplands is strong in April. The forest – a true hallmark of this valley – is completely dependent upon the San Pedro River and its subterranean aquifers.
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First, a note of sincere, heartfelt thanks to everyone who so generously contributed to my appeal for a new pair of binoculars! The appeal was a great success – I am elated to say that the new binoculars are in my hands, and they are absolutely stunning. I cannot adequately express my gratitude for the gift of such an exceptionally important tool that will enable me to continue doing what I do as a naturalist. I’m beaming as I write this. 🙂
White-nosed coatis are one of the most charismatic and fascinating native mammals of SE Arizona. Bands of them are fairly common in the Middle San Pedro Valley where my family and I reside, but I have rarely documented their presence on our property. Only days ago, my wife saw a lone individual close by our home. Two days later, a band of coatis crossed our little acreage unseen, but they left abundant and unmistakable signs of their presence.
Just south of the Arizona/Mexico border, coatis are known as chulos (there are several other Mexican names for them); in the US, most people refer to them as coatis or coatimundis. Taxonomically, they are known as Nasua narica. Among a number of their unique features, coatis are one of the world’s very few social omnivores. (Can you think of any others? Offhand, all I can come up with are humans and meerkats.)
Some two decades ago, when I first began to roam the wildlands of this valley, I was not sure how to separate the tracks of coatis from those made by one of their cousins, the raccoon. I had heard that they were difficult to distinguish, but that soon proved to be incorrect. This exemplified one of many things that a naturalist must learn by direct experience out in the field, for the great majority of tracking books fall far short of being accurate, reliable sources of information.
So, how does one recognize the differences between the tracks of these two animals – tracks that, ostensibly, can look a lot alike?
Fresh coati tracks in fine dust under my ramada reveal toes positioned tightly together with consistent thickness along the length of each toe.These raccoon tracks, particularly those made by the front feet, (at left), show diagnostic shaping and separation of the toes. The toes are proximally narrow in comparison to their distal ends, where they widen into bulbous tips with relatively short claws. Once this distinctive toe shape is recognized, misidentifications between well-defined raccoon and coati tracks can be eliminated.When a band of coatis forages, they commonly pause in certain areas where they make numerous shallow digs for food such as beetle grubs. The band that visited here just days ago left this characteristic array of holes behind. (Note the 6-inch ruler included in the photograph for scale.) Skunks are common locally, and they also dig for a living, but not in this fashion.On a hot summer day years ago, I photographed this chulo sign along the banks of the San Pedro River. The coatis had been digging into the sandy riverbank, leaving some spectacularly long claw marks in addition to the excavated holes.
Another pair of native mammals that can leave similar signs of their presence are mule and whitetail deer. One of several ways to distinguish their signs comes into play when these animals are moving at high speeds. Whitetail deer gallop when they run fast, but mule deer tend to stott when they are in a hurry. Stotting refers to an upward leaping motion where all four feet leave the ground at the same time and land at roughly the same time – a type of movement that most people would describe as a hop. And what a hop it can be!
A mule deer buck moving at high speed left a set of tracks near our home last week, beautifully defined in rain-moistened soil. This deer had easily leapt over two fencelines in less than several dozen yards and had clearly been moving very quickly. I laid a measuring tape on the ground along the deer’s trackway – it revealed a single stott that measured 19 feet, three inches in length. No problem for an adult mule deer.
Here are the four feet of the buck at one of the points where he landed. The deer did not stop here – these tracks were part of a series of energetic stotts. Note that the front feet are positioned ahead of the hind feet, (relative to the direction of travel). If the deer had been a galloping whitetail, this order would be reversed, (rear tracks to the front and front tracks to the rear). Note the spread clouts of the hooves. Deer (and many other mammals, including barefoot humans) autonomically spread their hooves like this in order to prevent slippage as they gallop or stott.
Darkness settles over the land. Many miles from the lights and sounds of towns and cities, Arizona’s Middle San Pedro Valley sprawls wild and still. At twilight, only a faint poorwill and a pair of great horned owls can be heard. The coyote telegraph erupts and then fades as it travels from ridge to distant ridge. In contrast to the rich variety of summer sounds, an autumnal hush blankets the countryside.
At day’s end, dusk gently ebbs into darkness as a brilliant October moon emerges from the far shores of the eastern horizon. Here, in our mesquite bosque, the peace and comfort of the night suddenly give rise to a thousand voices raised in the jubilance of courtship. These are sweet, almost melodic sounds – October’s distinctive nocturnal biophony. Tree crickets are singing from the ancient trees, thousands of them spread across the valley floor, their songs a vivid proclamation of thriving life within an otherwise quiet forest.
This species of tree cricket sings from the tall mesquites in our bosque. Its ecology is intimately connected to velvet mesquite trees. These are small insects with a big voice.
I have come to love the sounds of these delicate, gossamer-winged insects. Long after summer’s insect frenzy, when most species have faded from the scene, tree crickets come to life in the coolness of October nights. The males raise their transparent wings, then call to the females by stridulating – in other words, they rub certain parts of their bodies together to produce a surprising volume of sound. Females are drawn to these love songs. The males go one step farther by offering their mates a special reward. After mating, metanotal glands located on the dorsal side of the male’s abdomen secrete a substance that the female feeds on.
Eight species of tree crickets inhabit southeastern Arizona, where they produce two generations each year. The ones singing in local October bosques belong to the genus Oecanthus. Each species has its own unique song. However, even among the same species, sound can vary quite a bit depending upon air temperature. The frequency (or pitch) of the crickets’ songs increases as temperatures rise and slows as temperatures fall.
A bizarre butterfly landed on my screen door last week – an American snout butterfly, Libytheana carinenta. Last year, large numbers of these butterflies erupted all over the valley in late summer. Snout butterflies use their strange shape to blend in with their surroundings. When perched on a plant stem, their elongated “snout” breaks up the outline of their bodies, resembling a broken twig or a thorn. The range of snout butterflies extends all the way to South America. They are known for migrating across landscapes in huge aggregations.
A study in camouflage, the American snout butterfly sports wings that blend well with tree bark and a unique body shape that helps to conceal the insect when at rest.
This summer’s plentiful monsoon rains have continued well into October. Since the monsoon began on June 18, our rain gauge has recorded an amazing 13.46 inches of life-giving rainfall.
One of the local washes experienced some large summer floods. I took a walk down this wash with a friend a few weeks ago, to have a look at the powerful changes wrought upon the land by the big floods. What we saw was in stark contrast to the wash I had known from walks during the past several years.
During recent times, this broad wash had been covered by a wall-to-wall effusion of burro bush (Hymenoclea) standing six or more feet tall with a galaxy of roots anchoring the bushes to the ground. The flood had erased most of that growth, leaving behind a clear streambed lined with heaps of debris – tree trunks, plant material, rocks, and more. The floor of the big wash had been totally rearranged, its topography and course markedly changed during a couple of events that lasted only days.
In places where floodwaters form swirling, circular eddies, holes are dug into the wash floor like this one. These depressions can be very large and quite deep. They often hold pools of surface water that can last for months after flooding, a valuable offering to birds, mammals, and other wild creatures in this desert ecosystem.
Powerful floods like these transport thousands of tons of boulders, rocks, gravel, sand, clay, and a wide variety of organic materials – whole trees, cacti, and other plants. Downstream, entire soil profiles are altered and built as sediments settle from the turbid waters. Cutbanks collapse, dropping great layers of soil into the roiling floodwaters, releasing seeds that have lain dormant from ancient times into the present-day ecosystem. Old genetics from times long gone may invigorate plant populations and enhance the genetic variability – and hence, the viability – of modern plant communities.
Most people would simply label this collapse of a stream-side cutbank as “erosion.” That is an accurate use of the word, but I see much more going on here.
Debris piles left along the stream banks can be very large, consisting primarily of tangled, broken bushes, parts of trees, and other plant matter. They provide shelter and denning sites for small mammals, reptiles, amphibians, and other creatures. Floods are not all bad – they are simply a natural, intrinsic agent of change, some of it beneficial, some not. People often label floods as “bad,” but that viewpoint roots in anthropocentric thinking, a myopic way to view our world.
The ecology of many native species of plants and animals actually depends upon flood events. The beautiful stands of cottonwoods that line the San Pedro River could not exist were it not for floods creating the specific conditions that their seeds require for germination. The riparian forests that accompany the river depend upon having their roots tap into subsurface aquifers. The aquifers get recharged when floods happen.
As floodwaters recede, the bed of the San Pedro River leaves records of local wildlife in the drying mud. Here, the patterning of fine surface cracks results from a place where the river water subsided very gradually with little or no turbulence, resulting in the deposition of extremely fine clay particles. As these clay deposits dry, they crack in characteristic patterns.
October typically brings us the last ophidian visitors of the year, most of them not to be seen until next spring. A beautiful gopher snake was here last week, and as I write this, a diamondback is curled up a short ways from my entry door.
An October gopher snake, crawling along the wall of one of our buildings. This one was a male, measuring right around 63 inches in length. Always welcome here, as are all snakes.The year’s last generation of pipevine swallowtail butterflies occurs in October. I found this gorgeous caterpillar recently – it is either in the fourth or fifth (last) instar of its development, after which it will climb a plant stem and metamorphose into a chrysalis suspended by a single loop of silk as it waits out the winter season. The leaves visible in this image are pipevine leaves, (Aristolochia), the only plant that these caterpillars feed upon.
October is THE month for seeing pinacate beetles (Eleodes spp.) – they are literally everywhere at this time of year, easily noticed because of their large size, slow movements, and diurnal habits. When they feel threatened, pinacate beetles stop moving and assume this head-stand posture. If the threat escalates, (for example, when a bird tries to grab the beetle), the beetles fire a noxious, very disagreeable fluid from the tip of their erected abdomen. Chemical defenses are very common among many insect species.
Just a few days ago, I noticed this small tuft of feathers laying on the ground. Immediately, I began searching the area for more, because such a find usually indicates that a bird was recently preyed upon somewhere nearby.
I soon found many feathers like this, their shafts intact. Intact shafts indicate feathers that were pulled out, not bitten and yanked out as mammals do. So this was the work of a predatory bird, likely a Cooper’s hawk that I have been seeing frequently of late. This was a special find, for these feathers could have come from only one species, a gilded flicker. Gilded flickers are relatively rare in local bosque habitats.
The lightning bolt slammed into the ground with thousands of times the force and speed of a sledgehammer blow on an anvil. It struck so close to me that I heard no thunder, only the unmistakably loud, monstrously powerful “snap” that is characteristic of a bolt that hits far too near to its observer. I had been sitting on my bed reading when it happened; I knew instantly what had occurred, for this was not the first time that lightning had struck so close to me that no thunder could be heard. Many years as a guide in the wilderness mountains of Montana had brought me into near-contact with lightning along high ridges at timber line more than a few times. It is one of nature’s most lethal forces when it strikes living creatures, but the other side of lightning is that it is one of the world’s most quintessentially important life-giving phenomena. For the full story, see pages 204-205 in my book, The Life of the San Pedro River. The next morning, I found the place where the bolt had impacted. A tape measure revealed that the lightning had struck 53 feet away. The electromagnetic pulse from that bolt fried our telephone system and our computer router.
The storms of this year’s monsoon season in southern Arizona have been wonderful – thus far, our rain gauge has registered 9.56 inches of rain since mid-June, resulting in a grand resurgence of life all across this hot and formerly dry landscape.
On the morning of August 20, a serious storm pounded the ground with so much rain that the area around our buildings became an unbroken sheet of water. I could hear toads starting to call from our overflowing bird pond. Before long, dozens of spadefoot toads came out of their underground lairs to join in the party, all of them hopping and swimming through the flooded landscape in beelines toward the pond. This was a critical time for the amphibians, for in a normal year, they get only one or two brief chances to breed. It was also a rare sight, for I have never seen such activity in the daytime…but this was a doozy of a storm.
Mavis – the female half of the raven pair that we share habitat with – takes shelter from the storm under the roof of our shed.
As the rain subsided, I stepped outside. I heard the familiar roar of one of our local washes that had become engorged with flood water. A short walk of a quarter mile took me to a place where I could look down from the edge of a vertical cutbank at the flowing wash…
The view from the cutbank after 2.6 inches of rain from a single storm swelled Hot Springs Wash with roiling floodwaters. Only a single channel is visible in this image. The waters braided across the broad wash floor in an ever-changing – and growing – number of channels. Powerful floods are characteristic of desert washes with large drainage areas (this wash drains an area of about 100 square miles) and steep slopes in their headwater areas.
Next, I walked over to see what was going on in the little pond – there were eight pairs of Couch’s spadefoot toads in amplexus! A couple days later, after thousands of toad eggs hatched, our pond was teeming with wriggling throngs of tiny tadpoles.
Couch’s spadefoot toads mating in our pond. Each female usually lays hundreds of tiny eggs during such couplings, as the male releases sperm into the water.After the mating frenzy, myriad spadefoot eggs clung to every blade of grass afloat in the water.
Later in the day, Kathleen and I walked down the road to have a look at where the big wash crosses the road. The sound of the flood grew loud as we approached a point where we could see the flow, over 300 feet in width. The dirt road – the only road that serves the entire valley – had become impassable once again. In the midst of the turbulent flow, where the waters ran deepest, trees were being tossed around like toys, ripped from their root-bound moorings as they sped downslope toward the San Pedro River. Hundreds of tons of sediment, gravel, and rocks were being transported toward the floor of the valley in a rip-roaring tumult of rain water.
A view of the flood as it obliterated the roadway where it crosses the usually dry bed of Hot Springs Wash. During the twenty summers that I have seen this wash respond to rainfall events, only twice have I witnessed it running larger than this.
As we were watching the floodwaters, I climbed to a higher vantage point, where I discovered this beautiful Sonoran gopher snake. The snake allowed me to gently approach within a foot or so. This was a fine specimen, over 5 1/2 feet in length.
A few hours later, the sun had melted down into the nether regions of the western horizon. My wife and I walked outside around 11:00pm to listen to the night sounds. After turning off our flashlights, we witnessed something that is seldom seen here – fireflies!! Few of Earth’s creatures are capable of instilling such an immediate and compelling sense of awe and wonder as fireflies are. They were emitting distinctive, paired flashes of remarkably bright green light – in so doing, they identified themselves down to the species level. We were seeing southwestern synchronous fireflies, Photinus knulli.
A couple of days after the big storm, I walked down to the San Pedro River. Many areas within the river’s drainage had received substantial rains, bringing the river to life. Here, el Río is surging along with a flow roughly 180 feet in breadth and over six feet in depth.
Downstream, a group of turkey vultures was roosting in a pair of dead cottonwood trees. Dead trees are an essential and important component of all forested areas on Earth. All too often, humans fail to recognize this aspect of our planet’s ecology. Our culture – embedded in the ecologically dangerous Abrahamic concept of land use – (the land is here to produce our milk and honey, for human use) – tends to see dead trees as “going to waste.” “Salvage logging” of our national forests after wildfires is an exemplification this anthropocentric view of our living world.
The rainy season brings twilight flights of thousands of buprestid beetles just above the canopy of our local mesquite bosques. Here, a very rare sight unfolds as a female Polycesta aruentis everts her ovipositor to lay her delicate eggs deep within the sheltering crack of a mesquite stump, where they will be out of reach of the sun’s touch. Her larvae will hatch to bore their way through the wood, leaving tunnels in their wake that greatly facilitate the entry of fungi and other agents of decomposition. Thus, insects like this play a critically important role in forest ecology.
A half-grown (about four inches in length) Sonoran desert toad enjoys our bird pond after a rain. These amphibians grow to prodigious sizes. If I am not mistaken, they are the heaviest toads native to North America.
Living in remote parts of the desert southwest demands some important learned behaviors. Only fools step outside without looking first. This diamondback had just finished crawling across my entry steps when I took this photo. Snakes of all kinds are always welcome on our property – but continuous caution when one ventures outdoors is an imperative part of living here.
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The four young Chihuahuan ravens that were hatched this spring in a nearby mesquite tree have been exploring every nook and cranny of their expanding world. One of the four youngsters is a rare bird indeed, for it has a pied bill. (“Pied” simply refers to an object or creature that has two or more differing colors.) Both common and Chihuahuan ravens have black bills as adults. It will be interesting to see if this particular raven retains the pied colors on its bill as it matures into adulthood. The bills of its three siblings look quite different; they are well on their way to becoming fully black.
The young raven sporting a very unusual pied bill.In comparison to any of its siblings, the pied-billed bird really stands out.
On the third day of July, this desperately parched, drought-stricken landscape received the first measurable rainfall in many months. Our rain gauge registered a total of 1.47 inches from two storms that arrived in the afternoon and late evening. Summer “monsoon” rains are an exceptionally important aspect of southeastern Arizona’s ecology. The summer rains spark a surge of new plant growth, enable many insects and amphibians to reproduce, feed the trees, recharge critically important aquifers, and much more. Life blossoms on this land after the gift of rain.
The “snowbirds” (part-time residents) who run out of Arizona every spring and scamper back in the winter never have a chance to experience the glory and magic of the famed summer monsoon season. So much happens in Arizona’s natural world during summer. Many creatures that are difficult or nearly impossible to see during the other seasons make special appearances during the monsoon. Among these creatures are red velvet mites.
Red velvet mites remain hidden underground during most of the year, where they seek refuge in silk-lined tunnels. Only after a summer rain do these giants appear on the surface of the ground.
The word “mite” should immediately conjure images of very, very tiny creatures. Most mites measure under a millimeter in length. Velvet mites (classified in the family Trombidiidae) are among the world’s largest mites. Some species approach one half inch in length; the one in the photograph is about a quarter of an inch long. They are nearly impossible to miss, as their brilliant red color contrasts sharply with their surroundings. Mites are very important constituents of soil fauna and thereby play essential roles in many terrestrial ecosystems. Some mites even have a place in human medicine. Oils extracted from one species of velvet mite native to India have been traditionally used to treat victims of paralysis.
photo caption: An emergence of thousands of winged termites from a gap between two cement slabs on the morning of July 4th, just after our first summer rain.
Every summer, on the first morning following the first substantial rainfall, termites erupt in synchrony by the millions from their subterranean dwellings in a united, landscape-wide orgy of reproductive zeal. Winged males and new, winged queens flood from their underground homes to take wing, mate, and disperse across the land. This event is one of spectacular importance, for termites are among the most essential and beneficial creatures in this entire desert ecosystem. They are primary decomposers, able to break down cellulose and thereby recycle plant materials into the soil. Without them, the health of this living landscape would be in serious trouble.
A closer look reveals a mass of gossamer-winged termites – new queens and males – known as alates. They arise from these masses in great numbers like curtains of smoke, dispersing, mating, and flying off to start new colonies. After mating, the insects lose their wings, structures that evolved for the sole purpose of dispersal and genetic interchange.
Monsoon rains also bring many other creatures out of hiding. Tarantulas are common here, but they are not easy to find except during the summer, when rains stimulate them to leave their burrows in order to forage and find a mate. These huge spiders are formidable, armed with a pair of long, sharply hooked fangs and stinging hairs on their abdomens. It is hard to imagine eating a spider that is large enough to fill the palm of one’s hand, but there are a few brave creatures here who regard tarantulas as dinner items…
Sonoran desert toads are common valley residents here along the San Pedro River. They are the largest toads native to the United States, reaching lengths of nearly eight inches. This rare image was photographed by a friend as the toad was in the process of ingesting a daunting meal, an adult tarantula.
There is more to the above photograph than meets the eye. Frogs and toads possess remarkable viscoelastic tongues that fire from their mouths with great speed to catch their prey. Their tongues have a unique saliva that is phenomenally sticky; so sticky that some frogs in the genus Ceratophrys can haul in prey weighing more than themselves. This brings forth a question: how does a frog or toad get the prey item off of its sticky tongue once it is inside the amphibian’s mouth, so that it can be swallowed?
Alexis C. Noel, a Georgia Tech Ph.D. student specializing in biomechanics, published a scientific paper in 2017 documenting her research on the remarkable attributes of amphibian tongues and their saliva. What she discovered is physically, chemically, and biologically amazing…
Frog and toad saliva is a non-Newtonian fluid; the viscosity of the fluid can change based on how it is moved. When a frog’s tongue extends to impact a prey item, the saliva changes to a much more watery consistency, so that it can very rapidly coat the prey item and adhere to every part of the prey. As the impact slows to a stop and the tongue retracts into the mouth, the saliva returns to its normal thick, goopy consistency. This all happens in fractions of a second with incredible speed.
I recall watching many frogs and toads consume food items, mostly insects. Once the tongue returns inside the mouth with the prey item, the frog or toad retracts its eyeballs into its oral cavity, pushing the prey against the tongue. The push helps to release the prey from the tongue so it can be swallowed.
The promise of coming vaccinations, a new president, and the start of a new year have me full of hope… a state of mind that had faded considerably during 2020, a year marked by tragedy, social division, societal unrest, and a steadily worsening global pandemic.
Here in the Middle San Pedro Valley, the season of winter is at hand, although the use of a term like “winter” in a place like this is a stretch of the word. The coldest temperature I have ever experienced here was only 8°F., and snow rarely falls in the valley floor. The image above was taken on a winter morning when a rare blanket of fog had smothered the riverbottom forest with its cool, moist embrace. Fog is almost as rare as snow here. When fog does occur, it is a very transient affair, for desert fog most often dissipates into invisibility very quickly as the day warms.
A full moon casts its light on a stand of winter saguaros.
A few years ago, five inches of fresh snow fell overnight, gracing our bosque with a mantle of gleaming, sparkling white. I could not resist taking an early morning walk in order to read the very best of nature’s newspapers, for the goings on of every bird and mammal were written plainly in the snow. I encountered fresh tracks of various songbirds, quail, coyotes, a raccoon, mule deer, javelina, mice, cottontails, jackrabbits, and more. Following a set of roadrunner tracks (they are quite distinctive) I came across a sight I had never seen before: a roadrunner perched in a snow-covered mesquite tree.
I met with this well-chilled roadrunner perched in a velvet mesquite tree on a snow-graced morning.
Nature has forever been a source of inspiration for artists. There are scenes along the San Pedro River that could captivate any artist’s mind. Last month, an unforgettable gift arrived in our mail, an original painting crafted by none other than my brother, Rick. He and I had spent some time hiking in the riverbottom woodlands one fine spring day, when the river was alive with color and light. We stopped for a break at one of my favorite spots, a place that left its mark in my brother’s memory. Rick captured the essence of that place beautifully in this painting. What a gift!
