Category: graythorn

A Celebration of Birds in a Birdwatcher’s Paradise

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.”

An Inferno of a Summer, Huge Arthropods, and Arizona’s Tiniest Mammals

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.

A Fascinating New Bird Appears

A few months ago, an unfamiliar bird call became part of the daily biophony here on our home acreage in the Middle San Pedro Valley. As an ever-curious naturalist, I had to know what bird was uttering those strange calls. My wife, Kathleen, had noticed it too. The bird called frequently in the early and late hours of every day, taunting us with its unique, three-note call.

Binoculars in hand, I went looking. I slowly approached in the direction of the sounds, looking patiently and carefully. The local habitat consists of a mature forest of velvet mesquite trees. The sound seemed to be originating up in those trees, but no matter how much I searched, the bird remained unseen. Most often, as I approached too closely, the mystery bird would exit stage left and start calling from a new, more distant location. I tried on another day, and another. Every time, the maker of the calls remained elusive and sequestered.

Velvet mesquite bosque, the woodland where the mystery bird appeared. This is an image from the summer months.

One morning, after hearing the unseen bird again, Kathleen and I decided it was time to explore the  xeno-canto website. I know of no better website when it comes to searching for bird sounds; readers can find it here:  https://www.xeno-canto.org  

I had a growing hunch that we were hearing a thrasher…when we listened to the recordings of crissal thrashers, both of knew that the enigma had been solved.

The crissal thrasher visiting our bird bath on a cold morning when the water had frozen solid. Crissal thrashers average 11 1/2 inches in length. This species is known to form pair bonds (in preparation for the spring breeding season) as early as January. Just two days ago, I noticed that our thrasher had found a companion…

Why hadn’t I seen the bird? I had been looking up in the trees when I should have been looking down, at or very near ground level. The bird seemed to have the ability to “throw” its voice, making the calls sound like they were coming from above. Once we had learned the identity of the bird, we realized that we should have been searching for it on the ground, not up in the trees. Now, we see the thrasher every day as it hides beneath graythorn bushes, foraging for food.

Graythorn is indeed very thorny. Meant to discourage consumption by mammals, the thorns protect the plant, but when it comes to birds, these thorns are an attraction. They spell security from predators, especially raptors.

Crissal thrashers spend much of their time beneath thick cover, using their long, decurved bills to dig and rake away soil and duff in search of insectivorous food. Locally, these birds appear to have a very strong connection with graythorn bushes. Graythorn (Ziziphus obtusifolia) is the most common understory shrub in local mesquite bosques. It grows dense, tangled, thorny foliage, furnishing the perfect place for shy birds to seek cover in. I cannot overstate the ecological importance of these plants with respect to bird life. Many species of birds hide in graythorns, feed from the plant’s abundant berries, or nest deep within its thorn jungle of tangled branches.

At the time of this writing, the graythorn bushes outside my windows are in full flower. The blossoms are minuscule.

After the flowers have been pollinated, berries grow on the graythorn bushes, providing an important food source for many local birds and mammals.

This winter, the Middle San Pedro Valley has been inundated with unprecedented numbers of white-crowned sparrows. There are hundreds on our land every day, and in many other places as well. I cannot walk by any graythorn bush without flushing a throng of white-crowns from within. Like the thrasher, they forage on the ground and use graythorns for cover. Security is imperative to all small birds here, for bird-hunting Cooper’s hawks are present almost every day.