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 at Black Mesa in the hills 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 meets the Gila River. This area is known as Tres Rios (Three Rivers), because the Salt River also joins the Gila here. 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.

Thursday, August 14, 2014

Happy Valley Trails

One of the criteria at the top of our list when we were searching for a house in Phoenix twelve years ago was that we would be able to hike and ride our mountain bikes in the desert without having to drive more than ten miles to the nearest trailhead. Better yet, we'd be thrilled to have trails within walking distance from our front door. We found the perfect place, confirmed after a walk in the rain into Deem Hills Recreation Area from our prospective home just north of Happy Valley Road. Perhaps we became intoxicated by the sweet smell of creosote in the air, or captivated by the rainbow arching over the saguaro-studded ridgeline. A contract was signed the next day and we've been hiking and biking out our front door nearly every day since!

Miraculously, the number of trail miles to hike and bike near our neighborhood has multiplied over the past decade. The City of Phoenix expanded the formal trail system in Deem Hills from a few miles to over eight in 2010. A year later, fourteen miles were carved into the hills of the newly designated Sonoran Preserve just east of I-17, well within our ten-mile circle. Less than a year ago, twenty more trail miles were created, along with expansive parking and restroom facilities at Apache Wash, just south of Carefree Highway. To the south and west, Glendale's Thunderbird Conservation Park and Peoria's WestWing trail system double again our options.

These city parks and preserves are just a sampling of the network of desert trails that have earned the Phoenix Metropolitan area a spot in the top ten of the world's most Biophilic Cities, a program that recognizes urban areas that have intentionally incorporated ways for people to interact with natural landscapes into daily life. Grand designs for a 242-mile Maricopa Trail that will link all nine Maricopa County regional parks and a 336-mile CAP Recreation Trail planned to extend the entire length of the Central Arizona Project canal (CAP) are also underway, which would make the Central Valley of Arizona one of the most bike-able, walk-able and equestrian friendly suburban areas in North America.

Come see…and walk, or ride...for yourself!

Thursday, August 7, 2014

The Many Superpowers of Lesser Nighthawks

A sure sign of summer in Phoenix suburbs is the return of Lesser Nighthawks that migrate north from Central and Sough America to breed and feed in the Sonoran Desert, while at the same time, many people flee to escape the heat. Between late April and October, moonlit nights and early mornings are excellent times to catch a glimpse of these ghost-like birds, as they silently dance through the air catching insects. In dim evening light, flashes of white on the tips and tails of dark silhouettes may be all you'll see, but near a lighted ball field or street light, you can get a better look at the long, pointed wings and striped plumage that make them resemble a small falcon. Nighthawks are not hawks at all, though, and lack the fierce talons and sharp beak that are primary hunting tools for birds of prey. Instead, their erratic float-and-flutter flight pattern, wide mouth, tiny beak and tiny feet are some of their most notable features.

Their dawn and dusk, or crepuscular, feeding habits and gaping mouth earned them and others in their family of birds the common name, "nightjar." Somehow they were also dubbed "goatsuckers" because they were once believed to steal milk from nannies, but there is no hard evidence for this bit of folklore. The wide mouth has also led many naturalists to speculate that nighthawks are capable of picking up their own eggs and moving them away from would-be predators, or into shade during especially hot days, but again, well-documented observations are lacking.

However, it is true that nighthawks are masters of camouflage at every life stage. As adults, striped and mottled brown and gray feathers enable them to blend perfectly with rough-barked tree branches or a
pebbly desert floor. Unless you just happen to disturb one by walking near a nest or roosting sight, it is extremely rare to see a lesser nighthawk during the day, even if you are ardently searching for one.

A female nighthawk has the additional superpower of being able to tolerate surface temperatures over 110 F as she shelters her pair of eggs or newborn chicks with the shade of her own body. The mottled eggs are laid on open ground with not other nesting material to insulate them. After eighteen days of incubation, the downy calico chick hatch and are ready to fly within a couple of weeks.

One strategy that nighthawks use for keeping cool during our scalding summers is called "gulag fluttering," which is basically a kind of panting, or evaporative cooling. The extra wide mouth, in this case, acts like a miniature swamp cooler, helping to lower body temperature. Lots of birds do this, but nightjars can also vibrate their throats to enhance the cooling effect.

Acrobatic flight, deep camouflage and extreme heat tolerance are just a few of the nighthawk's superpowers.

What are yours?

Thursday, May 1, 2014

Javelinas in the Hood

The signs are everywhere if you know what to look for: seedy piles of scat; hoof prints in the dust; large bites taken out of cactus pads; shallow depressions in the shade of mesquite trees and the occasional tuft of coarse dark gray hair. If you have a good nose, you might smell their peculiar musky scent. Collared peccaries, better known as javelinas, are frequent visitors to many suburban neighborhoods in Arizona. However, unless you are nocturnal like they are, actually seeing one is quite rare.

Stetson Hills resident, Jennifer Moore, was once woken at 2:00 am by the sound of snorting and huffing outside her open window. When she looked out to see what was going on, there was a herd of eight javelinas trotting single file down the sidewalk. Another neighbor regularly sees them very early in the morning outside their view fence as the animals make their way to daytime shelters under nearby palo verde trees. A more recent report came from a neighbor who witnessed a pack of coyotes gorging on the carcass of a large javelina boar along one of the neighborhood trails.

Suburban habitats around Phoenix provide a smorgasbord of some of the javelina's favorite foods, including jojoba nuts, acorns, cactus fruit and pads, mesquite pods, agave, plus flowers, fruit and bulbs. Like their distant cousins, wild boars and pigs, javelinas are opportunists, so will happily eat your garden tomatoes, squash, birdseed or a bowl of dog food. By night they may be munching in  your yard, but during the day they will retreat up washes into the desert where they can rest unseen until the sun goes down. The Deem Hills are home to at least one small herd of javelinas that considers the neighborhood of Stetson Hills to be part of their territory.

They are named for their small spear-like, or javelin-shaped, tusks that grow from the upper jaw of both sows and boars. Also recognized by their peculiar flattened heads and long "collar" of bristly white hair, javelinas are reputed to have very poor eyesight, but keen senses of smell and hearing. They are common throughout the Sonoran and Chihuahuan deserts, all of Mexico and Central America and down into Argentina where they also inhabit tropical rain forests. In fact, paleontological research suggests that javelinas evolved in rain forests and have gradually extended their range to North American deserts. Archaeological evidence indicates that they did not inhabit northern and central Arizona until the late 1600's. Severe winter weather limits their range further north.

Javelinas are one of the few large wild mammals that breed year round, so it is not unusual to see pairs of tiny, red-haired piglets scampering to keep up with the rest of the family. About the size of a cottontail rabbit, the one-pound piglets are ready to run within a few days of being born. Although the mortality rate for javelinas is over 50% within the first year, those who make it beyond their youth may wander the desert for up to a decade. Humans, coyotes, bobcats and mountain lions are their main predators. Although javelinas are generally gentle animals, they do have a reputation for being aggressive defenders of their young. In any encounter with wildlife, it is best to not get between a mama and her babies!

As with most wildlife, javelinas are more threatened by humans than the other way around. To avoid any chance of unwanted aggression between you, your pets and a frightened javelina, refrain from artificially feeding or watering them, and keep pet food indoors.

Wednesday, February 5, 2014

Blackbirds: Pastry Surprise or Avian Pirates?

"Four and twenty blackbirds baked in a pie" is one of the more memorable lines in nursery rhymes passed on from eighteenth century England. There are many interpretations of this verse, but the two most cited are that there were actually recipes for live birds to serve as surprises at royal banquets; or that the entire poem is a secret code advertising for crewmen to contract with Blackbeard's ship.

In Europe, where this poem originated, one of the most common "blackbirds" is the starling, which was imported to North America in the 1890's as one of the menagerie of over sixty bird species mentioned in Shakespeare's writings. (The bard's play, Twelfth Night, is the oldest known source for the line "Sing a song o' six pence.") On many spring mornings, you might see starlings grazing local lawns and parks along with flocks of several types of North American blackbirds, which include cowbirds, grackles, Brewer's blackbirds, as well as the more colorful yellow-headed and red-winged blackbirds. This is especially true in winter months, when many birds congregate in mixed flocks while feeding.
Female grackles                                                        photo by Rick Halliburton
In the official blackbird family, Icteridae, males and females are often mistaken for completely different species because they look so different. Females' feathers are designed for camouflage, dressed in drab brown rather than black. Showy males are up to 60% larger than females and wear sleek black feathers with sheens of blue, green and purple. Blackbirds tend to thrive in the company of humans in both agricultural and urban settings, often in noisy flocks of hundreds, thousands or even millions. Because of this, they are often considered to be "pests," but there is also much to appreciate about blackbirds.
Male grackles in courtship displays                      photo by Rick Halliburton
The most elegant of this group are the male Great-tailed Grackles, with long fan-shaped tails, iridescent feathers and bright gold eyes. During their breeding season, the males perform ardent courtship displays featuring neck stretching, wing vibrations and tail fanning, accompanied by loud screeching and cackling. Some of this is competitive, so you'll sometimes see several males displaying at once as they vie for their rank in the local mating hierarchy. Both males and females are promiscuous, meaning that they all have multiple partners, although there tends to be more available females than males in most colonies. In this species, the ladies take care of nest-building and chick-rearing on their own. Thus, in some Hispanic cultures, a lazy husband who doesn't work is called a Zanate, one common name for a male grackle.

However, it is not completely derogatory to be called a Zanate, for they are also known as great vocalists. According to a Mexican legend, the grackle's diverse repertoire of whistles, chattering and squawks is said to represent songs expressing the Seven Passions of Life: love, hate, fear, courage, joy, sadness and anger.

Although the meaning of the nursery rhyme is ambiguous, one thing is for sure: if you take the time to watch a flock of blackbirds in their amazing synchronized flights, listen to their songs, or watch their elaborate courtship displays, you are sure to feel one of life's passions: joy!

Wednesday, January 1, 2014

From Down Under: Wattles, Kurrajongs & Gum Trees

Eucalyptus at a Phoenix golf course
One of the curious things about Phoenix is that there are more species of plants in the urban area than there are in the immediately surrounding Sonoran Desert. This is because we have imported hundreds of plants from other parts of the world. One of the highest-ranking countries for floral immigrants is Australia, with over eighty species of trees and shrubs that are cultivated and sold in garden centers all over the southwest. Since the interior of Australia is a desert very similar to central and southern Arizona, the plants adapt quickly to our equally hot, arid and sunny climate. A walk around the block of suburban neighborhoods around Phoenix is bound to take you past many Aussie ex-pats, especially wattles, gum trees and kurrajongs.
What wattles are to Aussies are known as acacias in North America. They all belong to the pea, or legume, family, but Australian acacias lack the spines or thorns that serve as self-defense from browsing mammals in North American ones. In place of thorns, the leaves of wattles contain alkaloids that are toxic to most animals. Over nine hundred of the world's thirteen hundred Acacia species are native to Australia. The most popular ones used for landscaping around Phoenix are the slender-leaved Willow Acacia (A. salicina) and Shoestring Acacia (A. stenophylla), both of which fill the air with sweet perfume from the puffball-like flowers every fall.
Kurrajong is the Australian aboriginal name for the bottle tree, a stout tree named for the shape of its trunk. The hard brown seedpods look like little canoes and the speckled maroon and white flowers resemble tiny jester caps. Indigenous people still use the bark of the tree to make fishing line, which is what "kurrajong" means in a now extinct language once spoken near Sydney.
Perhaps best known of the Australian flora are gum trees, or Eucalyptus, famed home of the kookaburra, a type of giant kingfisher. Just fifty miles west to Phoenix near Tonopah, Australian Outback boasts that it is "the worlds most extensive Eucalyptus browse plantation," providing North American zoos with leaves for captive koalas, which feed almost exclusively on Eucalyptus. There are seven hundred species in the world, and all but fifteen are native only to Australia. Here in Phoenix, around forty species are available through the garden trade. gum trees are revered for their beauty, shade and as fast-growing trees that provide wind breaks and screening in agricultural and industrial areas. That is why rows of eucalyptus are commonly planted along our roads and freeways and other not-so-scenic parts of the city, which is just about everywhere! Gum trees also make excellent pulpwood; the soft fibers are especially useful for making tissue paper. You probably have rolls or boxes of eucalyptus-based papers in your bathroom! In your medicine cabinet too, you may have throat lozenges, toothpaste or other cosmetics that contain eucalyptus oil.

Although it would be difficult to support a population of koalas in Phoenix gum trees, many native birds and insects have adapted to using them for food and shelter. most notably, monarch butterflies will roost and feed on Eucalypts during their annual migration. This is especially prevalent along the coast of California, where hundreds of thousands of monarchs roost during the winter months. In the annals of evolutionary biology, rapid adaptive responses to recently introduced species are a unique crucible for speciation. On the other hand, some people view any non-native species as a pest that interferes with the natural order of things, so many eucalypt forests are targeted for destruction, especially since they are also fire and windfall prone trees.

However, a special Red Gum (E. camaldulensis), affectionately known as "Mr. Big," is well-guarded and cared for not far from Phoenix at the Boyce Thompson Arboretum in Superior. The giant is reputed to be the National Champion of its kind, running neck and neck with a specimen in California at over one hundred forty feet tall and over six feet in diameter. Equally notable is Mr. Big's stats as the State Champion of all trees for height in Arizona, topping the runner-up Ponderosa pine in height by over thirteen feet!

Sunday, October 13, 2013


If you had lived among the Hohokam people in this area hundreds of years ago, you would have looked forward to a bountiful harvest of hornworms at the end of monsoon season. The edible hornworms are the caterpillars, or larvae, of white-lined sphinx moths (Hyles lineata), and are named for a short spine protruding from their rear ends. This year, thousands of these fat, green caterpillars were seen along desert trails and city streets wherever there was an abundance of their favorite food, a sprawling annual plant called spiderling (Boerhavia spp.).  On the autumn equinox, there were so many trying to cross the road at Happy Valley and 33rd Drive that some sections of asphalt turned a lovely shade of chartreuse. If you were lucky enough to see them up close, you might have admired the colorful pattern of black and green stripes, accented by red spots along their sides, one of nature's most colorful works of art deco.

Still today, some indigenous people of southwest deserts gather and dry bushels of hornworms for food. In southern California, the Cahuilla people call them "piyatum." O'odham people of southern Arizona named the host plant "makkum jeej," which means "mother of the caterpillar." If you are going to try this local delicacy, it's important to pinch the head off and shake the guts out before you skewer them on a stick to roast over hot coals, according to one 19th century ethnographer who learned piyatum foraging skills from the Cahuilla. 

Lizards and birds also feast on hornworms, dead or alive, head, guts and all.

These finger-sized caterpillars are just one stage in the life cycle of an even more fascinating and beautiful moth. After they have eaten their fill, hornworms burrow into the soil and change into a brown, pod-like pupa. This resting stage varies from two weeks to six months, depending on the time of year and latitude where they live. During this time, the caterpillar transforms into a moth, a mysterious process still not fully understood by scientists. 
Longer days of spring induce moths to emerge from the pupae after spending the winter months underground. Pupae are able to perceive light and therefore, the number of hours of sunlight in a day. Here in central Arizona, there may be several cycles of metamorphosis between March and September, with moths emerging within two weeks of pupating. Additional environmental cues, including soil temperature and moisture, ensure that pupae remain underground so that the moth's emergence will coincide with flowers to feed on and the right kind of plants to lay eggs on so that caterpillars will have plenty to eat. This is a well-orchestrated miracle!

Since moths are mostly crepuscular (a fancy term for being active during shadowy hours of dawn and dusk) or nocturnal, they favor white flowers, which are more visible in low light. They are also strongly attracted by certain floral scents. Their super long tongues allow them to slurp up nectar from deep-throated flowers like evening primrose, jimson weed, columbines and night-blooming cacti. In the process, their furry bodies are dusted with pollen, which gets transferred to other flowers as they go about foraging, making them important pollinators for some species. 

As adaptable opportunists, white-lined sphinx moths often fly in broad daylight and will feed on any color of flower that has sufficient nectar. Their adroit hovering skills and rapid wingbeats make it easy to confuse a sphinx moth for a hummingbird at first glance, but the brown and white stripes on their wings and flash of orange on the underwings are unlike any hummingbird. During a moth's two to three weeklong life, their primary mission is to mate. Females may lay hundreds of eggs that hatch within a week or so to begin the cycle again.

This is all really interesting, but after consulting with several entomologists and texts, I'm still left wondering: "Why do caterpillars try to cross the road?" Is it just to get to the other side? And is it true, as some naturalists claim, that they tend to crawl north? It turns out, no one really knows. The caterpillars are probably looking for more food, or soft soil to burrow into. But wouldn't the vast corridors of hot asphalt deter them from what is almost always a suicidal journey? Fortunately, although we may notice them mostly on roads, there is still plenty of desert land for hornworms to inhabit without having to navigate through heavy traffic.