The Middle San Pedro Valley sprawls across nearly one million acres of undeveloped, unfragmented land in southeastern Arizona. Its slopes and woodlands, bajadas and ridges have been rimed with frost every dawn under the abbreviated touch of winter’s Sun. Days are short. The land stands hushed and still with its seasonal absence of many birds, reptiles, and other forms of life. Nonetheless, there are many good reasons to get outside and walk the land. January and February have brought a few surprises, particularly in the way of unexpected sightings of locally uncommon birds.
In late January, five purple finches began frequenting our bird feeders, thinking they were well concealed within mobs of house finches and lesser goldfinches. My wife’s sharp eyes picked them out of the crowd. In 20+ years of avian record keeping in this valley, that was the first time we had ever seen purple finches. Another species that has been sighted sparingly here during the winter months is the American robin. For reasons that remain a mystery to me, we have been inundated with robins this winter. They bring me many fond memories of their near-constant presence during past summers when I lived in the northern states.
Speaking of thrushes, another bird that I had never seen in the valley before has arrived to grace the nearby riverbottom woodlands this winter – a Townsend’s solitaire. A friend and neighbor, Tom Talbott, first sighted one about a week ago in the forests along the river not far from our home. Tom is a highly skilled birder and a masterful wildlife photographer. A few days later, walking the same reaches of the river, a friend and I also saw a solitaire. News has been spreading of numerous sightings of this species in areas just a few dozen miles to the north.
A Townsend’s solitaire perches quietly in branches overhanging the channel of the San Pedro River. These elegant thrushes are common residents of timberline forests high in the mountains of western Montana, where I would meet them again and again as I led groups of hikers during the summer months. Their songs are unique and unforgettably angelic, like no other bird I have known. Photo courtesy of Tom Talbott.
Not far from the solitaire, we found this great horned owl snoozing within the branches of a Fremont cottonwood. These owls are remarkably capable predators whose list of possible food items exceeds that of any other North American owl. Among the creatures that great horned owls have been known to prey upon include insects, amphibians, various reptiles, mice, rabbits, domestic cats, small dogs, ducks, skunks, and even porcupines.
Mid-January brought us over an inch of rain in the valley floor during one winter storm. Rainfall amounts were much higher in the nearby Galiuro Mountains, resulting in a strong winter flow for Hot Springs Wash. Such flows during the winter months are rare.
The rain enabled millions of dormant London rocket (Sisymbrium irio) seeds to sprout, providing a new source of food for wildlife while greening the floor of this mesquite bosque with the glowing color of new life.
Large numbers of these small white puffballs erupted from the ground under mesquite trees after the rain. Fungi are becoming known as some of the most important organisms on the planet. The mycorrhizal filaments of many species of fungi form mutually beneficial associations with tree roots, for example. No forest on Earth can exist without such subsurface fungal alliances.
A hooded skunk wandered under my ramada one night, leaving its signature behind in the form of these tracks made in fine, dusty soil. Note the track pattern as the animal was walking at normal speed.
A closer look at the skunk’s footprints. Even though skunks are plantigrade mammals, the heels on their back feet often do not register in their tracks, as seen here. (The hind foot is to the left, front foot to the right.)
I discovered this torpid spiny lizard spending the winter brumating underneath a plastic tub that had been set outdoors on the ground. The lizard was found at ground level, not dug in below the frost line. Temperatures here routinely dip into the teens every winter. I was taught that reptiles must spend winters below the frost line, because otherwise they would freeze and die. I have also seen a pair of diamondback rattlesnakes spending the winter under a board in an open barn. Apparently, what I was taught cannot be correct – it seems clear that these reptiles can endure a fairly substantial amount of freezing.
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.
Thousands of harvester ants begin to rise into the air the morning after the desert’s first major summer rainfall.
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.
A living curtain of ants gains altitude, rising into the sky to begin journeys that will result in widespread dispersal across the land. Sights like this typically occur only on one single morning each year following the first monsoon rainfall.
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.
A rural road crossing on the San Pedro becomes impassable after rainstorms swell the stream. During most of the year at this location, the river is a mere six inches deep and less than ten feet across. When I took this photograph, the San Pedro had already receded quite a bit after a good run that had swelled the river to a width of over 150 feet and a depth of roughly 12 feet.
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.
A windfall of food for everything from mice to bears colors the floor of the bosque (Spanish for “woodland” or “forest.”)
These velvet mesquite seed pods are one of the most abundant and sought-after foods for local wildlife. They were also a staple food item in the diets of indigenous peoples.
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…
The fruiting body of this fungus sprouted from a mulberry trunk suddenly; within a matter of a few days it measured over 16 inches across.
A closer look – I believe this is Laetiporus sulphureus, commonly known as “chicken of the woods.”
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.
Rain awakens countless seeds long buried in the duff, coloring this desert world with chlorophyll, a synthesis of the merging of soil, sunlight, and water into life.
