Saturday, January 2, 2016

Heron Heaven

Great Egret

On any day of the year, if you visit one of the many suburban ponds or waterways scattered throughout the Phoenix suburbs, you will almost surely see one of our most elegant resident birds, a heron called the Great Egret. They are easy to recognize, standing at three feet tall with long dark legs, a slender yellow beak and pure white feathers. If you look more closely, you are also likely to spot several other species of herons: Great Blue Herons, Green Herons and Black-crowned Night Herons are better camouflaged, but share the same habitat. Another white heron, the petite Snowy Egret, about two feet tall with a dark beak and yellow feet, is also fairly common.
Great Blue Heron

If it weren't for Boston tea parties, however, we might not be able to witness the majesty of herons in our suburbs today. A little more than a century after the raucous dockside tax rebellion that ignited the American Revolution in 1773, two Boston socialites, Harriet Hemenway and Minna Hall, started another revolution in 1896 by hosting a series of more civilized gatherings to advocate bird conservation. Brought together over tea and biscuits, more than 900 women organized to ban the massacre of birds for their feathers.

During the late 1800's, the breeding plumage of adult Great Egrets was especially coveted by hat fashionistas. (Egret is derived from the French word aigrette, which means "silver heron." An aigrette is also the term for a decorative head ornament made with feathers.) These birds, and many other species, were nearly driven to extinction by hunters who provided feathers for the millinery industry. Efforts pioneered by the ladies of Boston eventually led to national and international laws that made plume hunting illegal. Egret populations have since made a dramatic recovery. This is one reason why the Great Egret was chosen as the symbol for the National Audubon Society, one of the oldest wildlife conservation groups in the country.

Long before we began building ponds and canals, herons have hunted along the Salt, Gila and Agua Fria rivers that once flowed freely through the Central Valley. Some of the birds are year-round residents; others winter here and return to breeding areas further north during the summer. Along wilder sections of the Gila River south of Goodyear (SW Phoenix), you can see large colonies of herons nesting and roosting in cottonwood and mesquite forests.

Anywhere there are fish, even if it's a small goldfish pond in your backyard, herons are able to detect their favorite food and may soar in for a snack. The Arizona Game and Fish Department, municipal Parks and Recreation Departments and local homeowner's associations assist with enhancing heron habitat by stocking ponds and reservoirs with fish. Although their primary intent is to provide angling opportunities for urban residents, herons and other wildlife benefit from fish stocking. Other ponds are stocked and managed specifically for wildlife, including a peaceful retreat in Glendale's Thunderbird Park at 59th Avenue and Melinda Lane, where special viewing blinds have been constructed for anyone who likes to sit and watch wildlife. If you are as patient and still as a heron, you may witness one catching its dinner.
Herons gather at a pond in north Glendale

Friday, October 16, 2015

Beyond Bermuda

A neatly trimmed lawn is perhaps the most iconic emblem of the American suburban lifestyle. Many people regard a cool patch of green as an essential ingredient of a civilized landscape, a symbol of serenity and order. Whether your favorite turf is in the form of a ball field, playground or a merely decorative feature of your own front yard, lawns are living communities of plants and animals, as well as recreational havens and design elements.

Bermuda Grass

The most common species join local lawns and playing fields is Bermuda Grass (Cynodon dactylon), a tough turf that was imported from southern Africa centuries ago to enhance grazing pastures. In the U.S., the grass is named after islands in the mid-Atlantic ocean that are presumed to have been a stepping stone to their introduction to North America. It is also abundant in southern India where it is called arugampul or doob and has been used for thousands of years as a medicinal herb to aid in healing everything from rashes to diabetes.

Also known as couch grass, devil grass, wire grass and dogtooth grass, this heat-loving plant is both celebrated and loathed for being hearty enough to survive the scorching hot and arid climate of Phoenix. In the same aisles of garden supply centers that sell 50# bags of Bermuda grass seed, there are also multiple chemical treatments available to attempt killing it. Fortunately, or unfortunately, depending on which side you are on, Bermuda grass is extremely persistent, partly due to the facts that roots can drill down more than two meters into the earth and that small fragments of grass can propagate into full plants within weeks. However, Bermuda grass is not tolerant of cold, hence an annual ritual of thatching and over-seeding with ryegrass is practiced every fall by those who wish to toil away at watering, weeding and mowing all year round for the pleasures that green grass provides. While the leave so Bermuda will wither and turn brown through colder months, the roots remain very much alive but dormant, ready to spring forth when soil temperatures rise again.
Kidney Weed

Even in perfectly manicured lawns, there is always more growing between the blades than the favored type of grass. Dozens of plant species thrive on the moisture and fertilizer that lawn cultivation provides. Among them are dandelions, spurge, chickweed, pigweed, lawn parsley and mallow. Most people call the interlopers "weeds." On a professional playing field, such varied textures may cause interference in the game, but if your main aim is aesthetics, you may want to consider nurturing a plush carpet of kidney weed (Dichondra repens) or cheerful heart-shaped leaves and bright yellow flowers of wood sorrel (Oxalis corniculata). And everyone loves searching for good luck in a patch of clover!
Wood Sorrel

Lawns also attract wildlife, both predators and prey. Cottontails feast on the grass; owls, coyotes and bobcats feast on cottontails. The larvae or caterpillars of furry orange butterflies called "fiery skippers" chew on the leaves, attracting all kinds of birds that forage for juicy grubs. Even more birds relish the times of year when people scatter fresh grass seed to primp up a sparse lawn. Numerous other species of uninvited grasses also make their homes in Bermuda turf. If left un-mown, a lawn can rapidly become a thigh high meadow full of wildflowers and insects. In Africa, Bermuda grass is part of the vast savannah that supports herds of rhinos an impala. Of course, this is not what we strive for in suburbia, which is why I've chosen to trade in my patch of Bermuda for artificial turf!

Monday, June 29, 2015

Flame Skimmer 

Bugs bigger than birds might sound scary, but most folks agree that dragonflies are more mesmerizing than fearsome. One of our local dragonflies, the Giant Darner, is the largest dragonfly in North America, with a five inch wingspan, and an equally long body. That's just a tad larger than the wingspan of some of our common hummingbirds! Although they are carnivorous, there's no need to worry: dragonflies don't sting or bite humans, but feast on bugs that do annoy us, like mosquitoes and gnats.

Since these fascinating insects are in the taxonomic order Odonata, the sport of dragonfly watching is called "oding." If you are beginner in the sport, you may just want to learn the difference between two major groups, or suborders, the damselflies (Zygoptera) and the dragonflies (Anisoptera), which can be distinguished at a glance. Dragonflies hold their wings horizontally at rest; the more slender damselflies fold their wings over their back when perched.
Powdered Dancer

Dragonflies and damselflies were not granted official common names until 1996. Before that, they were known mostly by their Latin family or species name; at least two dozen families and more than 5,500 species are currently recognized world-wide. A dozen or so species are commonly seen around suburban Phoenix, and more than a hundred are known throughout Arizona.

None of them can walk, but all are exceptional fliers, able to cruise at about 10 mph on average, and put o 30 mph, beating their wings at thirty times per second. They can move in any direction as well as hover, inspiring aeronautical engineers to study them in detail for clues to better mechanical design.

However, it is the monstrous looking aquatic larval stage that earned the group the common name "dragon" and the Latin name, Odonata, which means "toothed," for an over sized spiny jaw that extends like an arm to grab prey. Dragonfly larvae, also known as nymphs, live in freshwater ponds and streams where they hunt other insects, tadpoles and small fish. You can easily spot a damselfly nymph by the three feathery looking gills at the tip of their abdomen or "tail" and by the way they wiggle their body as they swim through water. The gills of dragonfly nymphs, in contrast, are inside their body. They move in quick bursts by squirting water out the end of their abdomen like miniature underwater jet boats.
Exuvia or husk of larva 

When a larva is ready to transform into an adult, it crawls out of the water, cracks open its skin right down the middle of its back, and slowly crawls out to begin a few weeks or months of life on the wing. In most species, males and females look very different, and like birds, the males are usually more brightly colored than the females. Male dragonflies are also territorial, and will chase off other males that intrude on their favorite stretch of stream or shoreline, but welcome females. Once he does find a mate, he latches onto her neck with special claws at the tip of his abdomen. The pair mate in flight, making a "heart" or "wheel" shape with their long abdomens. He will continue to guard her so that she can't mate with other males.

To complete the life cycle, a female will lay between 500-2000 eggs. If you see a dragonfly dipping the tip of its abdomen on the water while in flight, it is a female laying her eggs, one by one. Damselflies lay their eggs in the stems of plants where the hatched larvae can easily crawl into the water. Nymphs live under water between one and five years before emerging in their full glory as winged dragons and damsels. Hot summer days are the best time to spot dragonflies cruising desert washes and urban ponds where they patrol for meals and mates, so now is the time to get out your binoculars and do some doing!

Learn more about local dragonflies at a website created by ASU professor Pierre Deviche and dedicated to Arizona dragonflies.

Sunday, May 3, 2015


Sotol (Dasylirion wheeleri) has become a staple of suburban landscapes in southwest desert communities because of its beautiful form, drought tolerance and easy maintenance. Archaeological records show that the plant has been popular with people for more than 10,000 years. To Ancient Puebloans, though, the plants were not merely ornamental. They collected and used the leaves for fiber to make mats and baskets. Young tender stalks and roots were roasted for food. Dried sotol stalks were used as fire ploughs, a method of fire making in which a dry stalk is rubbed in a wooden trough until the friction makes a hot cinder. Sweet pulp from the sotol "heart" was used to make a fermented drink much like mescal or tequila is made from agave. This drink is still popular in some parts of Mexico.

Perhaps the most stunning feature of sotol is the huge flowering stalk that emerges each May from the center of a mature plant. After a couple weeks of daily measurable growth, the sotol in our neighbor's yard finally bloomed last year. The sixteen-foot tall stalk rose from the giant rosette of sawtooth-edged leaves, luring swarms of honeybees and tiny colletid bees that came to gather pollen. I've been amazed by the rapid growth of flowering stalks for over a decade, but did not realize until recently that sotols are dioecious, meaning that there are botanical equivalents of male and female plants.

Male plants bear long curly bunches of pollen-producing flowers, which sort of look like Cheetos, but without the orange dye. The sheer magnitude of the stalk and all of that pollen is truly astonishing. Likewise, females bear thousands of seed-producing flowers. Although the bees harvest prodigious amounts of pollen, they do not visit the female flowers because there is no nectar to attract them. The females must depend on wind to deliver pollen for fertilization. From a distance, you can tell the two types of stalks from one another simply by noticing the presence or absence of insect activity: male stalks are swarming with bees; female stalks may have a bird perched on top, but no bees.

Despite the fact that there are thousands of sotols growing in the Phoenix suburbs, you are unlikely to find one in nearby desert preserves. The natural habitat for sotol is much higher than our fair city, in scrublands and grasslands over 4,000 feet in elevation. They are most common in the Chihuahuan Desert, which extends from southeastern Arizona through New Mexico to Texas and Northern Mexico.

If you grow sotol in your yard, you can save yourself or your landscaper from hassling with the spiny leaves by letting it grow naturally rather than "pineapple-izing" the base. Although this practice may have been a way for ancient people to harvest leaves for fiber, there is no need to remove them otherwise. Better to sit back and enjoy a shot of sotol, or just admire these hearty and majestic plants in you desert landscape.

Saturday, February 7, 2015

What a Lizard Wants

A pair of Side-blotched Lizards  photo by Rick Halliburton 

When a lizard goes searching for real estate, their dream home has many of the same features we may have on our list: Beautiful landscaping, a sunny spot to relax in when it's cool, a shady spot to hang out when it gets hot, a neighborhood that is safe from predators and easy access to good food. They're not going to list granite countertops, but a large granite boulder to bask on would make a lot of lizards very happy.

Recent surveys in the Phoenix urban area by reptile biologists at Arizona State University have shown that, indeed, all fourteen native species of lizards in the area seem to prefer the same areas occupied by prime real estate. In an article called "Rich Lizards," PhD student Jeff Ackley and colleagues report that the diversity of lizards in the urban area is highest in more affluent neighborhoods. They call it the "luxury effect." Characteristics that tend to increase value for real estate also make for better quality lizard habitat. This includes: closeness to desert preserves, greater diversity of plants, more natural open space and less asphalt. Affluent neighborhoods also tend to have larger yards with more native plants and fewer lawns. A side benefit of all these features is that air temperatures are slightly cooler, especially during summer nights. This is because there is more shade during the day and a reduced "urban heat island" effect at night.
Regal Horned Lizard   photo by Kathy Darrow

However, each species of lizard has particular wants and needs that may limit where they can thrive, just as we humans all have various things that keep us most comfortable. What a Regal Horned Lizard needs most, for instance, is ants, and around here, a certain species of seed harvester ant: Pogonomyrmex rugosus. These ants prefer open flat areas where there are plenty of native seeds to harvest, so very few populations of Regal Horned Lizards have survived in the urban area. Flat ground is the first to go when development is planned.

Only two of the ten Phoenix desert preserves that have been surveyed have more of what Horned Lizards want: Deem Hills and Cave Buttes have enough flat ground to support healthy harvester ant populations. You will most easily find these reddish ants by looking for their nest holes, which are usually near the center of a 3-6 foot wide gravelly circle. After summer rains is the best time to watch harvester ants at work gathering seeds from afar, which they tore in special chambers below ground. Horned Lizards will seek out an active colony and snatch them up with their short, fat, sticky tongues. One of the ways biologist can tell if there are horned lizards around is by finding their fecal pellets (aka poop) nearby, which are masses of ant parts a couple of inches long.
Desert Iguana  photo by Brian Sullivan

What do other kind of lizards want?
*Desert Iguanas want creosote bushes to feed on and lots of space to run.
*Chuckwallas gotta have crevices to climb into, just the right size, so they can take a deep breath and wedge themselves in. Plus, they are picky eaters: palo verde, globe mallow and showy goldeneye are some of their favorite foods.
*Tiger Whiptails like rodent burrows to dodge into for shade and protection from predators.
*Ornate Tree Lizards want trees to climb, but vertical walls will do, and thus, they are the most abundant type of lizard in the urban area.
Ornate Tree Lizard photo by Kathy Darrow

What all lizards really want, though, is to be left in the wild with room to roam, places to hide and where it's easy to find their favorite foods. you can add a little luxury to an urban lizard's life, and maybe even boost your own real estate value, by planting native trees and shrubs in your yard, plus a large boulder or two for basking.

To learn more about local lizards, check out the website for "A Field Guide to Reptiles & Amphibians of Arizona" by Thomas Brennan and Andrew Holycross:

Tuesday, December 2, 2014

African Influence

Urban ecosystems are cosmopolitan, blending plants and animals, as well as people, from all over the world. In Central Arizona, there is a distinct African influence, especially in the wildly diverse succulent plants that are supremely adapted to hot, arid climates similar to the Sonoran Desert. In addition to fleshy leaves and stems, most succulent plants have thick waxy skin and specialized metabolism, traits that increase their ability to conserve water. Here is a small sample of the most common African succulents that you are likely to encounter in you daily life in the Phoenix suburbs.

Aloe (Aloe vera) has become an element of almost every American household because of its use in cosmetics, skin treatments, herbal medicine and food products, as well as for landscaping and for ornamental houseplants. There are over 500 species of Aloe, ranging from small rosettes to giant trees, all native to Africa and the Middle East. Many species have become naturalized in arid regions around the world wherever there are human settlements. (Agaves, which are native to arid lands in the Western hemisphere resemble aloes in form, so are sometimes called "American Aloe," but are not closely related.) The thick leaves of Aloe vera are filled with slimy gel that is extracted and marketed for everything from laxatives to sunburn treatments. The Bible references aloe as part of the embalming mixture used to wrap the body of Jesus Christ (John 19:39).

Moroccan Mound (Euphorbia resinifera) is one of hundreds of Euphorbias that have been imported from Africa for landscaping. Euphorbia is one of the most diverse plant genera in the world, with nearly 2000 species, including poinsettias and leafy spurge. Many African species of Euphorbia have spines as well as succulent stems, making them resemble cacti, which are indigenous to the Western hemisphere; this is a classic example of convergent evolution. If you look closely at the tiny flowers of Euphorbias like Moroccan Mound, you will see that they are completely different from showy cactus flowers. Most Euphorbias also have thick white sap, or latex; cacti do not. The sap of Moroccan Mound is called resiniferatoxin, and is renowned for being rated at 16 billion Scoville heat units, which is one thousand times hotter than pure capsicum, the spicy ingredient of chili peppers.  Handle with care!

Pencil Tree (Euphorbia tirucalli), also known as Firesticks because of the flaming red stem tips, is super easy to grow and can flourish into a large tree with little to no irrigation. Like most other members of the Euphorbia family, it oozes milky sap when a branch is broken or cut. (Natural rubber is made from the latex of another member of this plant family that is native to Brazil, Hevea brasiliensis.) Some have dubbed this plant a "miracle tree," claiming that the sap can be used to treat a broad suite of ailments ranging from warts to scorpion stings. However, beware! Many people suffer painful skin rashes and eye irritation when exposed to the sap or even just vapors from the plant. There are also reports that Nomadic hunters in Africa have used the toxic sap to poison their arrows for small game and to kill fish.

Elephant Food, Pencil tree and a columnar Euphorbia
grow together in a giant pot in front of a local grocery store

Elephant Bush (Portulacaria afra) was imported from South Africa, where wild populations of this evergreen succulent shrub are an important food source for elephants, as well as other wildlife, including tortoises. In Africa, they call it "spekboom." The cut stems of Elephant Bush easily regenerate into new plants, a characteristic that may have evolved as a symbiotic relationship with elephants, since they scatter plant fragments as they feed. There is some speculation by scientists that growing Elephant Bush on a large scale may be useful to store carbon dioxide in order to reduce atmospheric levels of the gas that contributes to global climate change. This would dovetail nicely with objectives to improve wildlife habitat in Africa.

To learn more about succulent species from all over the world, including cacti, visit your local chapter of the Cactus and Succulent Society, which holds monthly meetings at the Desert Botanical Garden in Phoenix.

Saturday, October 11, 2014

Skunk Creek: Heart of Northwest Phoenix, AZ

If you want to truly understand the Sonoran Desert, you need to walk the dry creeks and washes before and after a flash flood. In northwest Phoenix, Skunk Creek is the heart of the landscape, collecting water from sixty-five square miles of mesas, hills and bajadas.

A thin dotted-and-dashed blue line on the map, Skunk Creek is a seasonal stream that stretches about thirty miles from its headwaters on New River Mesa northeast of Anthem, to its confluence with New River just south of Bell Road and west of Highway 101. The creek bed runs roughly parallel with and between two other large washes, New River and Cave Creek, cutting a diagonal swath through dense suburbs. In the wilder sections, Skunk Creek is a quiet, sandy wash more than 360 days a year, where a person can walk up the middle following tracks of coyotes, black-tailed jackrabbits, lizards and roadrunners. And yes, there are skunks too, at least four kinds, that have historically roamed the corridor.

For thousands of years, Skunk Creek served as a travel corridor not only for wildlife, but also for ancient people migrating between the high country north of Phoenix and the Gila River in the south Central Valley. Today, we can still find signs of small settlements along the way, where people farmed maize, cotton and squash. Fragments of clay pots and stone tools are scattered around foundations of pit houses. Hundreds of people marked their passing by pecking petroglyphs in black basalt rocks at Hedgepeth Hills, just west of I-17 at Deer Valley Road.

Much of Skunk Creek is still as wild and free as it was just half a century ago when the north valley began to be developed. You can still walk the wash from its headwaters all the way to Carefree Highway. From there it begins to be tunneled under roads and channelized in order to control flooding that would normally spread for miles beyond the natural stream channel. In the heart of North Phoenix there is a paved recreation path, dubbed "Skunk Creek Linear Park," that winds above the wash for about four miles between 51st Avenue & Utopia down to 73rd Avenue & Greenway. The path connects with a network of city trails that follow other washes and canals. But when the big rains come and the creek starts flowing, you better find some high ground.

U.S. Geological Survey water gauge records show that on August 1st, 1964, Skunk Creek spiked to 11,500 cfs (cubic feet per second). This record high was trumped a couple of months ago on August 19th, when monsoon storms dumped nearly four inches of rain in the headwaters, causing Skunk Creek to surge over 13,000 cfs and jump its banks to flow down the I-17. That's about the same flow going through the Grand Canyon most days of the year. Imagine a small house (~1300 square feet) full of water flowing by every second. That's a LOT of water!

There was plenty of news coverage of that event and rescues that ensued when morning commuters encountered the deluge. But the real news is the life that thrives when the water recedes. Toads emerge and lay eggs. Seeds that may have been waiting for decades to be scoured and soaked, germinate. Shrubs and trees grow lush crops of new leaves. Flowers bloom. Insects hatch. Birds and rodents feast, and so do coyotes and bobcats. Life that has evolved here is well adapted to these torrential events, resilient to what may seem tragic to humans. A flash flood is lifeblood for the desert.

Know Your Watershed
Skunk Creek is a tributary within the Middle Gila Watershed, just east of New River. About three miles downstream from the confluence with New River in Glendale, water from Skunk Creek mingles with Agua Fria, which runs for a few more miles before it joins the Gila River. This area is known as Tres Rios (Three Rivers), because Agua Fria and Rio Salado combine to become the Gila River. About 200 miles southeast of Tres Rios, a little east of Yuma, all of the water from these drainages joins the mighty Colorado, which on a rare day, might reach the Sea of Cortez and the Pacific Ocean, another sixty miles south.