A Western Naturalist's Blog
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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.
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.
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.
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.
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.
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?”
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.
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.
So what is truly bizarre about this parasitic plant? Research has documented the fact that dodder actually steals sequences of DNA from 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.
Arizona’s spectacular monsoon season is in full swing this year. Here in the Middle San Pedro River Valley, we have received 7.28 inches of life-giving rain during the past seven weeks. Life of all kinds is emerging, much of it empowered by this season alone.
The strikingly beautiful Gila monster pictured above was photographed by my wife Kathleen just days ago. (One more reminder to my readers: if you don’t see that image, it is because you are viewing this in your email. Always go to my blog site – https://ralphwaldt.com – to see this post as I intended it, without omissions.) It is one of many desert animals whose activity increases or otherwise changes as a result of monsoon weather.
The world we live in has been under deep duress this past year; the global pandemic, political division, economic hardship, and numerous worldwide catastrophes have all combined to make many people feel stressed and depressed. That is the anthropocentric world. A wider view – beyond the human-centric world that we pay so much attention to – encompasses the rest of the planet’s glorious and infinitely varied life. When I feel overloaded after viewing the day’s headlines, I can always find a source of solace, reassurance, and joy simply by abandoning the vicarious, shallow world of my computer screen in favor of the outdoor world. All it takes is a few steps outside. Sunlight, vivid green plants, lizards, trees, bird song, fresh air… the real world is medicine for the soul.
One does not need to live in a rural area like I do in order to tap into the natural world. I have a friend who lives in suburbia, along the fringes of the immensity known as Dallas-Fort Worth. He spends time in his backyard where trees, shrubs, and a garden bring life and happiness into his world. There are no bears, cougars, or Gila monsters in his yard like there are here – but there is a diverse variety of life. My friend focuses his attention on smaller creatures and other forms of life; insects, lizards, and flowering plants, for example. He photographs what he sees – things that most people never even notice. The photographs from his back yard are often stunning, revealing a world remarkably rich in life captured by a talented, artistic photographer whose sharp observational skills remind us that life is everywhere, and that life is beyond beautiful.
With those thoughts in mind, I offer a series of recent images taken during the heart of the monsoon season here in the Middle San Pedro Valley of southeastern Arizona…
Mid-to-late summer is the most exciting time of year to be in southeastern Arizona; it is, by far, my favorite of the five seasons here. Locals know this time as the monsoon season, or simply, “the monsoon.” In a normal year, the majority of annual precipitation occurs during this time. Unfortunately, there were virtually no monsoon rains here in the Middle San Pedro Valley during the past two summers, resulting in a barren and desperately dry landscape. Thankfully, this summer has brought the gift of rain back to the land, with 3.38 inches falling at our location since early July, with more in the forecast. The result has been an explosion of life, much of which cannot be witnessed at any other time of year.
The tiny desert cottontail pictured at the top of this post is one of summer’s products. (A reminder to my readers: If you don’t see that image, it is because you are reading this in your email. Please click on the blog title to be redirected to my blog site (https://ralphwaldt.com), where you will see the featured image at the top of each post, and more that is not included in the email version).
Rabbits, (as opposed to hares – e.g., snowshoe hares or misnamed “jackrabbits”) raise their young in burrows and feed them milk for 3-4 weeks. After that time, the young rabbits are weaned and can leave the family group. This one was out exploring the world on its own for the first time. It was tiny enough to have fit comfortably in my cupped hand, and surely held a patent for cuteness.
The first substantial rain of the monsoon season catalyzes desert life. Harvester ants (and other types of ants) wait for that particular rain to enable the most important annual event in their lives. In early summer, the ants produce legions of special individuals deep underground, individuals equipped with wings. Their purpose is to reproduce and disperse across the landscape. The day after the first rains, tremendous numbers of winged male and female ants flood from their nests to mate, rise by the thousands into the air, and fly away. This is a true spectacle to behold, an event that typically can be seen on only one day of each year. Freshly inseminated females (queen ants) quickly dig out a new nest and begin to lay eggs, thus founding new colonies.
So why the big deal about ants? If I were asked to name some of the most critically important players in this ecosystem, ants would be at or very near the top of the list. They are extremely numerous – they mix tons upon tons of soil – they disperse large quantities of seeds – and they aerate the soil, allowing for better gas exchange from atmosphere to soil, along with enhanced rain percolation into the soil. These points do not tell the full story of how ants are crucial to ecosystems, but they do serve to shed light on their exceptional ecological importance.
Among the many effects of the summer rains is the repetitive flooding of the San Pedro River. The river grows rapidly after every major rainfall, sending torrents of flood water downstream. These floods are of great benefit to the riparian forests that line portions of the river’s banks, for they enable the cottonwood and willow trees to continue thriving as they recharge vitally important aquifers. These aquifers nurture the riparian forests and supply water for domestic and agricultural wells.
July brings the ripening of mesquite pods (or “beans”). This year, a good crop has literally covered the floor of the bosque. These pods – high in sugars, proteins, and fats – are a pivotally important food source for an incredibly long list of native creatures. Few, if any, native plants are more important or more beneficial than mesquite to this valley floor ecosystem.
In response to the photoperiod and summer’s warmth, rains, and raised humidity, many species of fungi reveal fruiting bodies. Among the most spectacular are growths of polypore mushrooms that emerge from the trunks of certain trees…
Due to a near absence of monsoon rainfall, the floor of our mesquite bosque has been barren of understory plants for the past two years. The great gift of this month’s rains have brought the color of life back to the land, vivid green that feeds my soul while providing food and cover for many living things from microbes to vertebrates. With just a few more rain storms, this mantle of new growth is capable of rising quickly to heights of six feet or more.
Early summer in the Middle San Pedro Valley has brought us some uncommon sights. One of our nation’s most dazzling – and sneaky – songbirds is the varied bunting. No larger than a small sparrow, varied buntings often appear black unless they are viewed at just the right angle in favorable light. They occur in small numbers here; we typically see only one or two of them in our bosque every summer. They are sneaky because we never know when they will appear, which is infrequently at best. A beautiful male will drop from the mesquites to grab a quick drink of water from our bird pond, then quickly disappear into the depths of the woodland, not to be seen again for days or even weeks.
Last week, a rare find presented itself in the form of a fresh Gila monster trackway etched into the fine dust along the side of our shop building. The only other animals that can leave similar trackways here are turtles, but a close look at this trackway leaves no doubt as to its maker.
The month of May brought the expected blooming of saguaros, but this year the huge cacti did something very strange. Instead of crowning the tips of their trunks and arms with halos of blossoms, they grew flowers both on the tops and down the sides of their heavy arms. I had never seen this phenomenon until this year. Locals are saying that this is a response to the severe drought we are experiencing in the desert southwest. I want to know why the plants are behaving like this.
First, an important message to my readers: For a much better experience, when you receive notice of new blog posts in your email, please be sure to click on the blog’s title. That will take you to my blog website, where the photographs are larger and the text is more readable. Also, there is a “featured image” at the top of every new blog post that does not appear in the email version. Do this now – you will notice a substantial improvement!
Summer has come to the river and its valleys, bringing a cavalcade of change to the animal world. Today, my thermometer registered 113° F. I don’t leave southern Arizona during the summer like so many people do every year. This is my favorite season here, because so much happens in the natural world during the fierce heat of summer…
This was one of those things that had to be seen to be believed. Recently, a friend sent me an email with some attached photographs of Chihuahuan ravens that he had taken in early May here in the valley. He kindly gave me permission to post his images on this blog.
In another instance, my friend was able to photograph a dispute between two ravens. The images appear to indicate a serious altercation. Such events are witnessed very rarely; even more rarely are they captured on a camera. I do not know what caused the aggression. It is nesting season for our local ravens. Perhaps one of the birds had tried to raid the nest of the other one, or was this a male vs. male squabble over a female? Only they know.
A few weeks ago, I received an an email from a local resident, one that had been addressed to many other recipients on the local community email list. I do not recall the exact title of the email, but it was something similar to “A Magnificent Visitation.” Attached to the email was a brief video depicting a flock of several hundred birds flying in coordinated patterns over the desert. The grace and wonder of birds in flight cannot be denied. I am sure that the sender of that email had nothing but good intentions. People liked the video. One neighbor even chimed in with comments referring to her happiness at seeing so many of these same birds at her feeders.
I was alarmed when I saw the video. I immediately recognized the birds in flight as a flock of brown-headed cowbirds. This was a larger flock of that species than I had ever seen in the valley. NOT good! Allow me to explain:
Brown-headed cowbirds are nest parasites (also known as “brood parasites”). They do not build nests nor do they incubate eggs or raise their own young. Those favors come from other birds, a list that tops over 220 species, including a wide variety of our songbirds. Female cowbirds are experts at finding the nests of other birds. They quickly lay their eggs during brief times when the host birds leave their nests to feed or seek water. Most birds do not recognize the alien egg, and proceed to incubate it as their own. When the egg hatches, a tiny, blind, featherless cowbird emerges to shove any remaining eggs or previously hatched young out of the nest. It remains there alone, to be fed and fledged by its unwitting foster parents, be they sparrows, warblers, vireos, or other species like the dazzling lazuli bunting pictured above.
The original niche that nature had carved out for brown-headed cowbirds in the area we now know as the United States was that of a prairie grassland bird that was closely associated with herds of roaming bison. The bison broke up the soil with their heavy hooves as they moved, exposing a banquet of food for ground-foraging cowbirds. There were other races of cowbirds in a few other locations, such as the inter-montane grasslands of central British Columbia. However, I do not believe that brown-headed cowbirds are native to southern Arizona. They are a relatively recent introduced species, likely first appearing here when they followed large herds of cattle that were driven into the region in the 1800s by Euro-American settlers.
The story of these birds does not sound so bad until one realizes some important aspects of their ecology coupled with the plight of our declining songbirds. Brown-headed cowbirds are flying egg factories. A single female cowbird can lay up to three dozen eggs in three dozen songbird nests every year. Considering that an average songbird nest would normally raise three or more young birds, that adds up to over 100 songbirds destroyed by each female cowbird every year.
North America’s songbirds have been rapidly declining in recent decades due to a variety of factors, all caused directly or indirectly by the activities of mankind. Here in southeastern Arizona, cowbirds are impacting our dwindling bird populations seriously. Like tumbleweed, buffle grass, or other non-native species, they are capable of wreaking havoc on ecosystems like this one that they are not endemic to. As a native species, the brown-headed cowbird is protected under the Migratory Bird Treaty Act… but native to where? What ecoregions?
I won’t tell my readers how I react to the presence of cowbirds here on our property, but I’d bet some of you can guess. All life is deeply beautiful and all life should be respected and revered. As I grow older, I embrace such tenets more and more deeply, but there are times when one must act to protect certain things. I never kill rattlesnakes, for example, even the ones that commonly sleep under our ramada, but when mice get into the engine compartments of our vehicles, decisive action is essential. Brown-headed cowbirds? Never welcome here.
