Among our most universal and compelling fears, one that is widespread across cultures, continents, and through vast spans of time, is the fear of snakes. In terms of simple survival, this makes perfect sense; many snakes can be lethal. For countless millennia, I am sure that people knew which snakes were dangerous and which were not.
In modern times, our culture has become so disassociated with the natural world that most of us can no longer identify what species are harmless and what kinds are not. The deep-rooted, possibly instinctual fear of snakes remains – when coupled with widespread ignorance, it results in the needless death of many snakes every year. You say rattlesnakes are easy to identify? Tell that to the many people who have killed slightly similar gophersnakes, thinking they were rattlers. Or to the screamers that wield shovels in attempts to automatically kill any snake they see.
The photograph above the title depicts a pair of mating western diamondbacks. A reminder – if you are viewing this in your email, you will not see the header images. Move your cursor over the title and click on it to be re-directed to my blog site, where the header images appear and where other images are larger as well.
What follows is a celebration of the beauty, grace, and elegance of the remarkable animals that we call snakes. Thirty-four species inhabit the Middle San Pedro Valley. Here is a sampling of a few that I have had the delight to encounter…
A Sonoran coralsnake, (Micruroides euryxanthus), a highly fossorial, nocturnal, (and therefore seldom-seen) species. The striking aposematic coloration of these beautiful reptiles is a clear warning to many would-be predators. Bites from these small snakes are very rare – and very serious. The venom is primarily neurotoxic; drop-for-drop, it outdoes any other southwestern snake for sheer potency.Sonoran coralsnakes are small, (rarely over two feet in length) shy, and retiring, preferring to hide their heads when threatened rather than strike defensively.
Gophersnakes, (Pituophis cantenifer), are Arizona’s longest serpent, capable of reaching lengths of over eight feet. These powerful constrictors are experts at preying on rodents. A special scale armors the front of their snout, enabling them to push through soil in rodent tunnels with ease. Gophersnakes play a key role in landscape-scale ecology by controlling rodent populations. This also makes them an ally to ranchers and farmers.
Sadly, many are killed by ignorant people who mistake them for rattlesnakes, and many more are intentionally killed by drivers, brutal acts that are a mark of cruel, simple-minded people.
While gophersnakes are common in Arizona, this one is very rare due to the aberrant patterning on the upper parts of its body. The usual dorsal blotches have been replaced by long, striped markings. Glossy snakes, (Arizona elegans), are quite common in the Middle San Pedro Valley. This species can attain lengths approaching six feet. At a glance, it is not hard to confuse these snakes with gophersnakes.
A Sonoran lyresnake, (Trimorphodon lambda), curled up against the wall of my adobe residence. Lyresnakes are fascinating; their large eyes feature vertically elliptical pupils, whereas most of our other snakes have round pupils. This is a nocturnally active species whose its diet is composed primarily of lizards. Lyresnakes don’t have injectable venom; instead, they secrete venom from glands in the rear of their mouths that is very toxic to lizards – but not to humans.
A typical “pink” coachwhip, (Masticophis flagellum). Coachwhips are often erroneously called “racers” or “red racers” by local residents. Coahwhips are phenomenal creatures, the true “über predators” of the southwest. Equipped with large eyes capable of exceptional long-distance acuity, coachwhips are the desert’s fastest snakes, and are surely among the fastest in the world. These are extremely alert reptiles that specialize on hunting lizards but will also consume a wide variety of other prey items. Coachwhips occur here in three color phases, with intergrades as well. The pink phase predominates locally.
I spotted this long-nosed snake, (Rhinocheilus lecontei), crawling across the dirt floor of our open shed on a warm, early summer morning. Its vivid colors and patterning are a reminder that snakes can be very beautiful creatures.
Long-nosed snakes occur in southern Arizona in two main color morphs. This is the other one, a completely different mix of colors and patterns compared to the individual above.
A California kingsnake, (Lampropeltis californiae). To me, this is one of the most beautiful snakes in Arizona, combining a chain-like pattern of cream-yellow bands set against a glossy, satin-black background. Kingsnakes are snake specialists, actively hunting many other species including rattlesnakes – kingsnakes are immune to their venoms. In addition to snakes, other foods include small rodents, eggs, and lizards.
A desert kingsnake, (Lampropeltis splendida) This species occurs locally in two primary color phases – the one pictured here is the most common. Some desert kingsnakes exhibit melanistic (all black pigmentation) coloration.Checkered gartersnakes, (Thamnophis marcianus) prefer habitats near water sources such as streams and ponds, where one of their favorite types of prey can be found most reliably – amphibians. Three species of garter snakes inhabit the San Pedro River Basin.
Rattlesnakes are the victims of more prejudice and brutal cruelty from people than all other American snakes – most often, the prejudice and cruelty arise from deep ignorance. We tend to overlook the comforting fact that rattlesnakes are among the very few toxic snakes on Earth that give us the courtesy of a warning. This western diamond-backed rattlesnake, (Crotalus atrox), is one of several that I see quite often around our buildings. Bites from this potent species are very serious, but also very rare IF one simply pays constant, close attention to where one’s feet and hands are placed when outdoors. We never kill these snakes, (nor any others, for that matter). Most diamondbacks are shy and inoffensive if left alone. Quite abundant in many habitat types, diamondbacks play a very important role in local ecology by helping to control rodent populations.
Of the world’s 36 species of known rattlesnakes, surely the black-tailed rattlesnake, (Crotalus molossus), would win one of the top prizes for sheer beauty. My wife and I spent half and hour watching and photographing this unagressive, beguiling individual. We found it basking, suspended several feet off the ground among tree branches in a walnut – velvet mesquite bosque. This one was large for its kind, close to 48 inches in length.
I had to radically adjust my search image for local rattlesnakes when I uncovered this snake in our shed, an Arizona black rattlesnake, (Crotalus cerberus), curled up beneath an inverted wheelbarrow. Before that moment, my search image had concerned itself only with the grays and dull browns of western diamondbacks; black rattlesnakes were not “known” to inhabit low-elevation places like our valley-floor bosque, situated at 3,100 feet. Since then, I have recorded this species locally several more times.
The Mohave rattlesnake, (Crotalus scutulatus), is the most potent rattlesnake in the entire American west, injecting substantial amounts of strong neurotoxic venom when it bites. This one emerged from under a stack of lumber that I had been working with, furnishing an unforgettable reminder that only fools slip their hands under wood stacked outdoors without looking carefully beforehand.
The most reliable way to visually identify Mohave rattlesnakes is to get a close look at their supraocular scales that lie atop the head between the snake’s eyes. It is difficult to do this safely without a good pair of binoculars with close-focusing ability. Diamondbacks can look quite similar to Mojave rattlesnakes, but their supraocular scales are much smaller and more numerous. Adding to identification difficulties, the two species have been known to hybridize in Cochise County.
Small and inoffensive, ring-necked snakes, (Diadophis punctatus) are common in the San Pedro River Drainage.
When threatened by a predator, ring-necked snakes may flip themselves upside-down, feigning death while revealing their striking, aposematically-colored ventral side.
Eastern patch-nosed snakes, (Salvadora grahamiae) feel like smooth satin when handled. This species is always among the earliest to emerge when the weather begins to warm in the valley, often above ground by mid-March. Note the heavy scale at the proximal end of the snake’s head, armoring for its snout as it digs underground in loose soils.
Upon lifting a pile of old branches and debris one day, I exposed this incredibly tiny snake, a highly fossorial species I had never seen before.
My first thought was, “I never knew earthworms lived on our bosque,” until I looked closer and picked it up. Coiled in my palm with room to spare was this amazing western threadsnake, (Rena humilis). Threadsnakes prey on ants, ant eggs, ant larvae, and termites. They are a favorite prey item for Sonoran coralsnakes.
Replace ignorance with knowledge. Be kind to snakes.
Few places in the United States can rival the watershed of Arizona’s San Pedro River as one of the nation’s premier birding hotspots. A phenomenal richness of birds has been documented here – well over 450 species. Join me as I celebrate this gift of life with a sampling of our beautiful, diverse, and fascinating avian fauna…
One of the rarest colors among all the creatures of planet Earth is blue, here brought to brilliant life by a male blue Grosbeak, (Passerina caerulea).
The broad-billed hummingbird, (Cynanthus latirostris), tiny and utterly dazzling, underscores the need for a pair of good binoculars to enable full appreciation – not to mention a heightened sense of wonder – of this jewel-encrusted sprite. Unfortunately, it has been dubbed with one of the dullest and most unimaginative of names.
Hummingbirds are important pollinators of many native plants. Here, a fitting example of coevolution presents itself: the saguaro evolved to raise its flowers high into the desert air as an offering to flying pollinators like bats and hummingbirds. The bats and the birds are able to locate these tall beacons at long distances. The height of the saguaro’s blossoms ensures that its pollinators will remain secure and at ease, out of the reach of a long list of ground-based predators.
Ravens are the most intelligent birds in our country – they possess larger brains relative to their body size than any of our other species. Ravens also have the largest vocabulary of all American birds, they mate for life, and they can live for decades. These black-as-night birds are absolute masters of flight. Magic attends all ravens. This is Mavis, a female Chihuahuan Raven (Corvus cryptoleucus), who has successfully raised many broods here on our property with the help of her mate, Mike.
A fledgling raven spends months with its siblings and parents, exploring and learning about its world. During that crucially important period in their lives, the young birds meet many of their neighbors for the first time. Adult box turtles like this one have little to fear from the fledglings, but neonate turtles are a favorite food.
Cooper’s Hawks, (Accipiter cooperii), are what instill constant wariness and universal fear in most other birds of smaller or equal size. These hawks are specialized, highly skilled bird hunters. Utilizing the combination of a long, rudder-like tail, lightning reflexes, powerful flight musculature, and incredibly sharp eyesight, they are among the world’s most capable avian predators.
The sight of a Crested Caracara, (Caracara plancus) in the Middle San Pedro Valley is a rare treat. Caracaras are classified as members of the Falconidae, the falcon family. The crested caracara is the world’s second largest falcon.
Elegant, gorgeous, and highly social, Gambel’s Quail, (Callipepla gambelii) are common valley residents. The ecology of this species is closely linked with Gila monsters, for quail eggs (and occasionally young chicks) are a major food source for the big lizards. Greater Roadrunners, (Geococcyx californianus), are a frequent sight here, but seeing them in snow is anything but common, for snow is rare in the valley floor. Their tail feathers display are an eye-catching blend of beautiful iridescent greens and bronze. Roadrunner populations are locally cyclic, but what determines that is something I have yet to learn.
Lark Sparrows, (Chondestes grammacus), are a great example of why no one should be without a pair of binoculars. Seen with the naked eye, they are just another small, drab brown bird. Viewed through binoculars, these sparrows come to life with ornate patterning and rich, saturated colors.
A Loggerhead Shrike, (Lanius ludovicianus) scans for its prey from an elevated perch in a velvet mesquite. “Loggerhead” refers to the shrike’s unusually large head. (The largest non-pelagic turtle in our country also shares this moniker with the shrike: “loggerhead snapping turtle.”) Shrikes sometimes impale their prey on long thorns and even on barbed wire. This beautiful predator has been in sharp decline all across its range for decades. Loggerheads are the only shrike endemic to the United States. Dressed in vivd red hues, Northern Cardinals, (Cardinalis cardinalis) are a visual standout in any habitat type – that is why cardinals tend to spend much of their time concealed in dense shrubs or other types of thick cover. In the valley, cardinals have a very close association with graythorn (Zizyphus obtusiloba) bushes, where they find safety and peace of mind within the thick maze of very thorny branches that so characterize graythorns.
As humans, we tend to conceptualize and visualize birds either in flight, or as viewed laterally (from the side). I think this posterior view of a northern cardinal may outdo any other viewpoint – what an amazing crest!
Decades ago, Spotted Owls, (Strix occidentalis) ignited a huge controversy when they were added to the endangered species list. Many people lost sight of the fact that it was not just the birds that mattered, for spotted owls were a symbol for what really mattered most: the ecoregion itself – the magnificent coastal rainforests of our westernmost states that have literally been torn to shreds by humanity’s rapacious demand for wood products. Few people know that these owls are also residents of the Sierra Madrean Ecoregion. Sometimes known as “Mexican spotted owls,” this subspecies – Strix occidentalis lucida – reaches the northern tip of its range in the San Pedro Watershed. During a very lucky day, I photographed this individual in the Huachuca Mountains.
There are few more vivid ways to mark the coming of spring to the Middle San Pedro Valley than the arrival of Vermillion Flycatchers, (Pyrocephalus rubinus). These tiny birds light up the fields and bosques in early March – before the mesquite trees leaf out. Adult males are wearing freshly grown feathers in March, plumage so pure and bright that these minuscule flycatchers can be seen with the naked eye at distances approaching 100 yards. Their crowns sport the most radiant part of their plumage, hence the name “Pyrocephalus,” which translates to “flaming head.”
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.
I am happy to report that the Middle San Pedro Valley has finally received some summer rain! This has been a very dry summer – during July and August, we have received only .63 inches of rain. Most of that has occurred during the past four days. The summer “monsoon” season is what literally defines this ecosystem – enabling much of the rich assemblage of plant and animal species that makes this part of Arizona such a remarkable place.
Despite the extended drought, the velvet mesquite trees in the local bosque have put on a tremendous spurt of foliar growth this year. Additionally, the trees have flowered three times since spring. As I write this, the ground under the trees is plastered with a heavy crop of “beans,” the nutrition-packed seed pods that are one of the cornerstone food sources for our wildlife. How can this happen during such a bone-dry, hot spring and summer? The answer is rooted in last year’s very wet monsoon season. Mesquites have a remarkable ability to move rainwater down their roots, where they store it at depth for later use. That’s right; these trees can move water in both directions in their root systems! The big bean crop owes its genesis to last year’s stored rain water.
Wind plays a pivotal role in the ecology of velvet mesquite trees. When the seed pods are ripe, winds accompanying rain storms can release astounding quantities of pods in very short periods of time. Pods on the ground then become available to all wildlife, not just the species that climb trees. Mesquites depend upon animals to remove the tough outer seed coating by chewing and gnawing on the pods. The seeds of mesquite trees are able to germinate only after the outer husk is removed. This beautiful bumblebee appeared last week, an uncommon insect in local bosques. The ecology of bumblebees is intimately woven around the activities of small rodents. Local bumblebees make their colonial nests in the abandoned underground nests of mice and kangaroo rats.
Iridescent scales glitter on the back of this Clark’s spiny lizard, at rest in the shade of my ramada on a 108°F. day. Prime habitat for this species are mesquite bosques, where the trees offer an abundance of shade and escape routes from predators. Clark’s spiny lizards can climb trees with the speed and agility of an over-caffeinated squirrel.
Within the sheltered confines of a small depression in the joined trunks of two mesquites is a small rodent’s dining room – in this case, likely an Ord’s kangaroo rat. Note the many chewed fragments of mesquite pods. Kangaroo rats and many species of mice prefer such places to gnaw on their foods.
As of this writing, the raven family is still together as the trio of young birds explore their new world, constantly learning from their devoted parents. That’s papa Mike in the foreground, Mavis in the background, and their rowdy, inquisitive kids in between.
Mavis eyes up one of her favorite foods. Large eggs like this one must be held in the bird’s beak with skill and finesse. She sauntered off with this one, walking some 90 feet into the bsoque, then gently dropped the egg, dug a hole, placed the egg into the hole, then covered it with soil and duff. The spatial cognition and spatial memory of ravens is astounding. Hundreds of food items get stashed in tree crotches or buried for later use – with uncanny ability, the ravens remember where every one of them is hidden. This morning brought us a seldom-seen spectacular visitor in the form of this Gila monster that was crawling along the foundation of our home.
When viewed dorsally, the reticulated patterns on the backs of Gila monsters really stand out – patterns that are mirrored in the art of many native southwestern cultures and tribes. No two Gila monsters are patterned alike, so photographs can identify specific individuals. This one is an adult, about 14 1/2 inches in length.
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.
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.
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.
There has been a sudden and tremendous eruption of small beetles in the local mesquite bosque. A dense, tall understory of pigweed, (Amaranthus palmeri) covers the floor of the woodland, an exuberant growth enabled by recent monsoon rainfall. When I walked into these plants this morning, curtains of tiny beetles took flight from the pigweed at my every step, thousands upon thousands rising upward like a reverse blizzard.
The leaves of the pigweed plants had become dotted with countless small holes during the last two days. This morning, the plants revealed that an orgy of feeding had taken place during the night. Literally all of their leaves had been reduced to a ghostly remnant of reticulated veins with no leaf tissue left in between. Every plant, everywhere I looked – consumed overnight.
Acres and acres of bosque understory were fed upon by an almost inconceivable number of small insects. The plants looked almost shredded.
A pigweed leaf after the night’s heavy feeding spree.
Naturally, I had to know what these beetles were. They were diminutive, measuring around 4-5mm in length. Up close, the beetles were beautiful, sporting brightly colored, broad white bands running lengthwise across their shiny black elytra. After some research, I learned that they were known as “pigweed flea beetles,” Disonycha glabrata. Their ecology entails a close relationship with specific host plants – they will feed only on plants in the genus Amaranth. I have witnessed dense growths of pigweed during most of my summers here; I had noticed these beetles in prior years, but never in such spectacular abundance. Why had their population so suddenly rocketed this year? I can only guess. Perhaps this year’s rains were perfectly timed at just the right intervals and in perfect amounts to encourage such an event? Maybe it has something to do with their predators…or some other mechanism?
A pigweed flea beetle, Disonycha glabrata.
When insects erupt in large numbers, people are often quick to react with alarm and negative attitudes. Yes, they shredded an entire forest understory – but was that a bad thing? Or simply natural change? It is not our place to pass judgement on what happens in the natural world. Both the beetles and their host plants are native constituents of this ecosystem. So, I do not necessarily think that what has happened is somehow wrong or alarming, but it is interesting.
I found another creature wandering in the pigweed last week – a young adult Sonoran Desert Tortoise! We see these reptiles rarely here in the bosque; they are more partial to nearby upland desert habitat types. This one’s carapace was between 9 – 10 inches long, and like most of its kind, it was cautious, slow-moving, and appeared unfazed by my presence.
The Sonoran Desert Tortoise that I discovered resting peacefully under the trees. This reptile and its close relatives have recently undergone taxonomic revision – to scientists, it is currently known as Gopherus morafkai.
The tortoise’s powerful front legs are clad in rows of thick, hard scales that assist in digging and may help the turtle resist serious injury from predators. When threatened, the tortoise tucks its head in and then covers its front with these remarkably well-armored legs.
A few days ago, I went out on a walk with a naturalist-friend. He shared a special area with me, a mature mesquite bosque with a remarkably rich, lush understory. I was deeply touched by the feel and presence of this almost subtropical woodland. The image below provides some insight into the kind of verdant growth that this “desert” valley is capable of hosting.
A jungle-like wall of vining plants drapes over young trees and shrubs in one of the most lush, beautiful velvet mesquite bosques I have ever seen. Just beyond the reach of this image was a barbed-wire fenceline. On the far side of the fence, cattle grazed – the ground under that part of the forest had been virtually wiped clean, transformed into a deeply impoverished world with respect to native plants and wildlife. Mesquite bosques as rich and fecund as this one have become very rare – cattle are commonplace. How is this right?
