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.”
The desert is ever so quiet lately; bereft of nearly all bird song and the scurry of lizards, the hushed glide of snakes, and the plod of tortoises, autumn stills the land. Despite the fact that it is now early December, the cottonwood stands along the river are just now coming into full color, normal timing that can seem so late, given the other species of cottonwoods that I grew up with in more northerly climes. Life sometimes demands a closer look, especially during its seasonal ebbs. Here is a gallery of some of the little things that still manage to crawl or fly about in these cooler times…
Jerusalem crickets are large, chunky insects that spend most of their time concealed under objects or under ground. One of their diverse genera, Ammopelmatus, (unique to the western US and Mexico), is currently known to contain well over 20 species. Among their common names in Mexico is Niño de la Tierra, or “Child of the Earth.” The heavy, spiked legs visible in this image are adapted for digging. The huge head houses powerful musculature that enables a very strong bite. Jerusalem crickets drum their abdomens on the ground to attract mates. They leave distinctive tracks on dusty roadways that show drag marks left by their heavy abdomens. And yes, the “I look like a big, striped, stinging insect” is a great example of aposematic coloring.
As the summer floods draw to a close, moist banks of mud remain for many weeks – even months – along certain reaches of the San Pedro River. Here, a statement in brilliant color comes to life as a group of thirsty Southern Dogface Butterflies, Colias cesonia, drinks from lingering monsoonal rainfall trapped within flood-deposited clay sediments. The name “dogface” originates from patterns seen on the inside of the wings, uncommonly noticed since this species rarely perches with its wings open. Several species of carpenter bees inhabit the San Pedro River Drainage. Despite a detailed search, I could not find a match to identify this species with its pair of striking red head spots. Carpenter bees are big, impressive insects that chew their way into wood, constructing tunnels where they raise their young. I have watched them boring into live mesquite trees, an astounding feat, for mesquite is an incredibly tough, dense hardwood. Their tunnels can approach lengths of twelve inches. A fleeting touch of bright orange reveals a Leafwing Butterfly, Anaea spp., whose host plants are limited to crotons. I know of very few lepidopterans native to the desert southwest that can rival this species for such sheer, saturated, brilliant orange-red coloration. When at rest, with wings folded, this insect virtually disappears into the foliage, living up to its name. Like most people, I have seen countless spiders in my lifetime, but very few have been colored like this one, known as a Green Lynx Spider, Peucetia viridans. Measuring between 5/8 – 3/4 of an inch in body length, this species is capable of taking down prey as large and formidable as carpenter bees. Like all their kin, lynx spiders manufacture silk, but do not make webs; their silk is used to anchor them when jumping, and to attach egg sacks to vegetation. They also have a defensive trick that few other spiders possess – the ability to squirt poisonous liquid at an attacker up to a foot away. Late in the year, as foliage often yellows, this spider is able to change its color from predominantly green to pale shades of yellow. Photo by Kathleen Waldt.
A Plea For Help
Naturalists, like all professionals, require tools in order to do their work. I can say without hesitation that my most important tool has always been a pair of binoculars. Naturalists are literally disabled without them. My trusty pair of Zeiss binoculars have finally reached the end of their lifespan, after 33 years of near-daily use. I am seeking help in replacing them, for professional-quality optics are never inexpensive. If you would like to consider this sincere plea for assistance, please click on this link:
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.
For many living things, effective camouflage often means the difference between life and death. I have witnessed camouflage acts that left me amazed – snowshoe hares in winter, whose fur matched the color and reflectivity of snow perfectly, or the disappearing act of a snipe crouched in grass…but lately, I witnessed a larval insect whose camouflage made my jaw drop.
One of the strangest caterpillars I had ever seen…
The creature had brashly exposed itself by falling from its perch in a velvet mesquite tree to land on a hand railing that had been painted white. It had gone from near invisibility to “How could you possibly not see me?” in the blink of an eye. Clinging to the railing was a slow-moving, two-inch caterpillar cryptically colored with dull greenish-gray skin. Hair-like filaments extended from its prolegs to form a peripheral fringe around the caterpillar’s body. The filaments served to effectively break up its outline. As if that were not sufficient, the crypsis of this larval moth went a step further, for the caterpillar’s body was quite flattened. In cross section, most caterpillars are round or somewhat ovoid, but this one had a cross-sectional shape more like a thin, gently curved crescent. This unusual shape meant that the dull-green, fringed caterpillar could literally melt into a twig or a branch to cloak itself in obscurity like a ghost in a fog bank.
Later, some research revealed that the creature in question was a lappet moth caterpillar, possibly of the genus Gastropacha. The word “lappet” is used to describe a fold or flap in a garment or headdress. Thus, lappet moths (family: Lasiocampidae) get their name from the hair-like fringes that project from their larvaes’ prolegs.
A lappet moth caterpillar that had fallen out of its element – transformed from profound obscurity to blatant visibility.
During the autumn of 2021, discoveries here in the surrounding mesquite bosque included this banded gecko that had dropped into an old bucket. These velvet-skinned reptiles are common here, but remain well hidden and inactive during daylight hours. Geckos are among the few truly nocturnal constituents of Arizona’s rich saurian fauna. I found this young glossy snake hidden beneath an old piece of plywood on the ground. Glossy snakes are often mistaken for gopher snakes. These beautiful, innocuous reptiles can reach lengths of nearly five feet. They are among this area’s most common serpents. Their scientific name is a gem: Arizona elegans.
The 2021 monsoon brought a cavalcade of change to the Middle San Pedro Valley. Late in autumn, large numbers of Empress Leilia butterflies (Asterocampa leilia) could be seen adorning the landscape. Abundant rainfall spurring rapid growth of their food plants likely played a major role in the eruption of these insects. Their caterpillars feed on desert hackberry, Celtis ehrenbergia (formerly pallida).
Take a walk in a local bosque late in late autumn and you are likely to see what look like little clumps of snow in the distance, gleaming white patches that really stand out on the dark-colored floor of the woodland. A closer look reveals a surprise; a mass of seeds from an unusual member of the dogbane family known as climbing milkweed, Funastrum (formerly Sarcostemma) cynanchoides. Unlike most other types of milkweed plants, climbing milkweed is a true vine, ascending to heights of 10-12 feet in tall shrubs and trees.
It is hard to miss the contrast between a clump of climbing milkweed seeds and the floor of the bosque.
After pollination, the flowers of climbing milkweed form pods that eventually fall to the forest floor, where desiccation causes them to split open and unfurl a beautiful array of seeds embedded in a mass of gleaming, silvery-white filaments.
A closer view reveals numerous seeds, the future of the species encapsulated within each one. Climbing milkweed is a host plant for the larvae of both queen and monarch butterflies.
Individual seeds can be carried long distances by wind currents, effectively distributing the plant’s progeny across the landscape. Wide distribution of seeds enhances the probability for successful germination and the continued success of the species.
The 2021 monsoon season in southeastern Arizona has certainly been one of the most memorable. At our home acreage in the Middle San Pedro Valley, 9.81 inches of rain have graced the land since the rains began on the second day of July. Other locations within less than 40 miles of us have received over 16 inches! The result is a landscape – and an ecosystem – burgeoning with a refulgence of renewed life. Since regional records have been kept, only the 1955 and 1964 monsoon seasons can compare. The scene above, featuring a landscape bursting with fresh, vivid green growth crowned by a rainbow is emblematic of Arizona’s monsoon.
As the monsoon wanes, migrant birds visit our feeders and watering places; notable appearances this year have included large numbers of Nashville warblers and an exceedingly rare blue bunting, a species that has never been “officially” recorded anywhere in Arizona. As the season approaches autumn, many changes occur in the world of reptiles and insects as well. Rattlesnakes are moving toward their hibernacula sites. The year’s last generation of butterflies brings flashes of beautiful color to the ecosystem. Other insects are reaching maturity, such as several types of native grasshoppers and katydids.
During the past two weeks, great numbers of mature lubber grasshoppers could be seen in many places in the valley floor. Their presence and abundance are a reflection of the monsoon rains that have enabled an explosion of plant life – a smorgasbord for grasshoppers. At this time of year, these bulky creatures have reached their final instar and are actively seeking mates.
A mature lubber grasshopper, Brachystolla magna. It is normal to see large numbers of these heavy, slow-moving insects during the tail end of our monsoon season. Note the tiny vestigial wings – this grasshopper is incapable of flight.
In mid-August, just after an afternoon rainstorm, I watched a female ornate box turtle emerge from the bosque to drink from a rivulet of rainwater. As she was slaking her thirst, I caught a flicker of movement some forty feet beyond her at the edge of the trees. It was a male box turtle. He had spotted her, and this was mating season. If you think turtles are slow, you have never seen an amorous male box turtle chasing a female! There is nothing subtle about box turtle sex. The males literally run down and attempt to corner the females, who move nearly as fast in their attempts to elude the charging males. Once the pair is joined, mating can take upwards of an hour.
A male ornate box turtle in hot pursuit of a prospective mate. I have seen this happen a number of times; what is most amazing to me are the distances at which the males first spot the females when the chase begins. In relatively level areas with open ground, males can visually discern females located at least 30-40 feet distant. Once a female is spotted, the male immediately makes a beeline to her at top speed.
The chase ends with a successful mating, allowing the circle of life to continue as it has for countless millennia.
Last week, my wife Kathleen discovered a new species of beetle, (one we had never seen here before), floating in a rain collection bucket. She rescued the hapless insect – a gorgeous, iridescent creature known as the Carolina tiger beetle.
This glittering, multi-colored tiger beetle got a new lease on life when it was rescued from a full water bucket.
Tiger beetles are incredible insects. The have been a part of my life since boyhood, when I often attempted to catch them as they raced across the ground with what seemed like otherworldly speed. Very few insects are faster on land than tiger beetles. Tiger beetles are hyper-alert predators equipped with unusually long hind legs for rapid propulsion. Their big heads house a pair of huge compound eyes capable of acute long-distance vision. The visual field of a tiger beetle encompasses more than a full hemisphere. When a prey item is spotted, tiger beetles run it down, then secure their meal with a set of long, formidable, serrated mandibles.
A lateral view of the Carolina tiger beetle, Megacephala carolina.
Most species of tiger beetles are diurnal, but the Carolina tiger beetle is an exception, preferring to be active after dark. I wonder if any part of these insects would glow under a UV light source? A number of other local nocturnal creatures glow under ultraviolet light, including scorpions and pocket gophers.
Butterflies are often abundant during the monsoon. As I was working outdoors one day, I noticed a fresh chrysalis hanging from some old wire fencing. I recognized its form; it had been made by a caterpillar that was a member of the butterfly subfamily Danainae. Insect species native to Arizona that belong to this group comprise three look-alike species: monarch, queen, and soldier butterflies.
The chrysalis hatched in a short time – only a week or so – to reveal a gorgeous queen butterfly. After hatching, the butterfly clings to the shell of its empty chrysalis, pumping blood into its unfolding wings.
Once the butterfly’s wings have expanded to full size, it is normal to see the insect remain perched for some time as it slowly opens and closes its wings, readying itself for its maiden flight.
Many plants native to the desert southwest have specially adapted themselves in a variety of ways to the summer monsoon season. One of the weirdest, most bizarre, and fascinating is a plant known as dodder. The first time that I encountered dodder, I stared in sheer wonder for some time while thinking “what the hell is that?”
Patches of dodder are a common sight during the latter half of the monsoon season.
Dodder grows as a vine, commonly forming a scattered profusion of very fine, yellowish tendrils that snake their way through the vegetation. It is a plant that cannot manufacture chlorophyll. Dodder survives by obtaining water and nutrients from other plants – it is an obligate parasite.
A closer look at dodder, (genus Cuscuta).
The weirdness begins just after a dodder seed sprouts following a monsoon rain storm. The minuscule seed – nearly microscopic – sends a small, shallow root into the soil while raising a tiny, thin tendril above ground. As the tendril grows, it starts to turn in upwardly-ascending spirals. It is not seeking light as most plants do – it is searchingfor a host. As the tendril lengthens, its spirals correspondingly enlarge, until it makes contact with a nearby plant. The tip of the tendril is chemosensory; it can literally sniff out what sort of plant it touches. Dodder is selective about the company it keeps – only certain plants will do as suitable hosts. If the tendril likes what it senses, it wraps itself tightly around the plant’s stem, then sinks a feeding tube – known as a haustoria – into the stem.
At this point, the seedling’s tiny root dies. The dodder plant then obtains all of its water and nutrients from its host. It will continue to grow and search, attaching itself to more plants. Once it has inserted enough feeding tubes into its victim(s), dodder reaches a point in its physiology that enables it to reproduce. Clusters of tiny white flowers erupt from the vine’s stem, ensuring the plant’s future.
Our local species of dodder sprouts clusters of small, white flowers – these grew from a dodder vine that had entwined itself on the stem of a pigweed (Amaranthus palmeri) plant.
So what is truly bizarre about this parasitic plant? Research has documented the fact that dodder actually steals sequences of DNAfrom its host plants’ genes, then incorporates them into its own DNA. The process is called “horizontal gene transfer.” This results in better survival for the dodder plants. It also enables them to manufacture strings of RNA that it sends back into the host plant, causing the host to weaken its defenses.
Dodder plants are classified as members of the Convolvulaceae – the morning glory family – with over 200 species worldwide. The genus, (Cuscuta), has a global range, occurring in tropical, subtropical, and temperate habitats. Dodder has a slew of common names, many of them derogatory – strangleweed, witch’s hair, devil’s guts, scaldweed, devil’s hair, and hellbine.
When considering this plant, we should strive to avoid the common propensity of our species to pass judgement on other life forms….often the result of our high capacity for arrogance-as-a-species combined with ecological ignorance. Simply because dodder is a parasite does not make it bad. Estimates place the percentage of parasitic organisms on Earth at 40-50% of all species. Clearly, parasitism is an essential part of the recipe for life on Earth. Here in the Middle San Pedro Valley, one of dodder’s favorite host plants is pigweed. Even when heavily infested with dodder, local pigweed plants continue to grow and produce viable seed.
