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.”
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.
