Rigor Vitae: Life Unyielding

Sunday, May 28, 2023


 This is the time of year when one of our most mysterious bird species returns to our area from its wintering grounds. With an 18" wingspan, the Black Swift is significantly bigger than other North American swift species. It was never common, but over the past half century, its overall population seems to have decreased by about 90 percent. It looks very much like a larger version of the much more common White-throated Swift, only its plumage is completely blackish. Some individuals have whitish tips to the feathers of their undersides, and for a long time this was presumed to be a characteristic of juvenile birds. A recent study found that it tends to be a mark of female birds of all ages, although it's not a dependable way to distinguish the sexes, as some females lack the white tips and some males have them. The white tipping also tends to be more distinct in juvenile birds. The sexes can be reliably told apart by the shape of their tails; those of males are distinctly notched, while the females' tails are not. The only place I know of in Utah where Black Swifts reliably nest is Mount Timpanogos. When you hike to the top of that mountain in the summer, you can usually spot one or two flying about high in the sky, if you keep your eyes open. Black Swifts have also been recorded in Iron, Kane, Sevier, Washington, Cache, Salt Lake, Duchesne, Uintah and Wasatch Counties. Like other swifts, they spend all day aloft, even sleeping while flying, in a technique known as "aerial roosting." Normally, they only land to nest. A crevice in a rock face, usually behind a waterfall, is selected as a nest site. A single egg is laid, and both parents care for the young bird. They bear a throat pouch that they can fill up with insects caught on the wing. Once the young bird is flying well, in about mid-August, the family disappears. For a long time, nobody knew where they migrated to, until a couple of years ago, when researchers in Colorado fitted four Black Swifts with geolocators and managed to retrieve three of them the following year. All three birds had followed roughly the same route to winter in western Brazil. What sort of habitat they exploit or how they live is still unknown, since there are still no documented sight records of Black Swifts in Brazil. We only know that they make it back up to our region around the end of May. The IUCN lists the Black Swift as "vulnerable," with an estimated population of 170,000 mature individuals.

Tuesday, March 15, 2022

Since yesterday was "Save A Spider Day," I should have posted about the Joro Spider, but that didn't occur to me until now. This spider has been the subject of a lot of hysterical media coverage lately. It was accidentally introduced into the southeastern US about six years ago and has established itself in parts of Georgia and South Carolina. One of the stories told about this spider is that they can transport themselves by "ballooning" on a strand of thread. What the stories don't mention is that they do it as hatchlings, just like a lot of native spiders do. Here's a short video I made about ballooning and other forms of transportation that tiny animals employ:



Today is Buzzard Day, the day that Turkey Vultures typically return to Hinckley, Ohio from their wintering grounds. That's not very interesting, so let's talk instead about that word "buzzard." It's an American colloquialism, of course, for Turkey Vultures and their relatives like Black Vultures, but like many common names for American animals, it was bestowed by settlers with vague knowledge of wildlife in general, upon the wrong birds. The true buzzards are a group of raptors that includes our Red-tailed and Red-shouldered Hawks. Had the early English colonies been populated by zoologists, we'd surely know these birds as Red-tailed Buzzards, Red-shouldered Buzzards, Swainson's Buzzards, etc. Calling the buzzards of Hinckley "vultures," though, isn't exactly correct, either. The New World birds we call vultures belong to an ancient lineage that's quite different from the true vultures of the Old World, which are more closely related to the sea eagles like our own Bald Eagle. The late ornithologist Dean Amadon used to suggest using the word "condor" for all New World vultures (Turkey Condor, Black Condor, King Condor, etc.), and that's an idea I'd happily go along with. There are a lot of other examples of these confusing American wildlife misnomers. Another good one is the name "Elk," which was given to a large American deer that's much more like the European Red Deer than the animal that should have received that name, which we call a Moose. Can you think of some others? (The painting is of a California Condor, a bird whose name I have no gripes about.)

Sunday, November 22, 2020



Wednesday, March 20, 2019


Today is World Sparrow Day, a day to celebrate one of the most successful of Human commensal species, the House Sparrow (Passer domesticus). Commensalism is the dependence of one species on another in a relationship just a bit south of true parasitism. A number of human commensals are familiar, the Norway Rat, Black Rat and House Mouse, the Common Starling  and Rock Dove--creatures despised and maligned by most. It's pretty tough, though, not to be charmed by the jaunty little House Sparrow. The black bib and bright brown back of the male can be seen bouncing merrily along sidewalks throughout the world. A poet friend of mine used to call them “Party Birds.” In falconry slang, the word “Spug” is borrowed from old Scottish. I think either term works well.

The taxonomical placement of the Spug and his 20 or so congeners has been the subject of much debate. Not closely related to the American sparrows, for years they resided in the weaver family, Ploceidae, then found themselves lumped for a time with the family Estrildidae, which includes most of the well-known cage finches. Today most authorities follow Sibley in placing them in the family Passeridae, along with pipits, wagtails and accentors. Most anywhere in Africa and Eurasia one or more Passer species is native, and a number of them have been human commensals for millenia. The Eurasian Tree Sparrow (P. montanus) has pioneered frontiers as far-flung as Missouri, but it's P. domesticus that has shown true genius at the art of commensalism, with a present range that extends from Australia through urban and rural situations in both Americas. Spugs have learned to thrive in a variety of settings, often living their whole lives indoors, successfully breeding in shopping malls and warehouses. There is even a record of a pair successfully raising a brood in an English coal mine 640 meters below the ground.

Toward the end of the nineteenth century, Eugene Schieffelin, a British expatriot living in New York City, embarked on a little project that would secure his place in ornithological history. Obsessed both with birds and Shakespeare, Schieffelin set out to introduce every bird species mentioned by the Bard into Central Park. Today we remember him as the Victorian ninny who brought us ecological doom in avian form, but what's often forgotten is that Shieffelin was a member of an “acclimatization society,” one of many groups dedicated to redistributing favorite animals and plants. During this time, such projects were all the rage, but were almost invariably failing propositions. Schieffelin's starlings and sparrows thrived well enough, but let's not forget his Eagle Owls, Blackbirds, Nightingales, and all the others doomed to bachelor deaths in the Big Apple

Young Spugs grow quickly, and can fledge at less than two weeks of age. It is normal for a pair to fledge three different broods in a season, and as many as seven broods have been recorded. Their fecundity and willingness to eat nearly anything helped them spread across the North American continent in a few decades, radiating into new ecological niches, and showing astonishing physical change in well under a century, the big, dark birds of the Pacific Northwest contrasting with their small, paler brethren of the desert Southwest and their brightly-colored Eastern kin.
As they've invaded new spaces, English Sparrows have had their effect on the ecology at large. Far slower than any native passerine bird, their presence has affected the behavior of certain predators. In many American cities, the once bashful Cooper's and Sharp-shinned Hawks have taken up urban living, and in the winter are exceptionally common now in many cities, a fact I attribute to the Spug. In 1980 a friend and I found a Cooper's Hawk nest in the heart of Salt Lake City. At the time I could find no previous citation of an urban Cooper's nest in the literature. Today it's hard to swing the proverbial dead cat without hitting one, or at least attracting its attention. American Kestrels  have also learned to exploit the easy quarry, and in doing so, I believe have become more ornithophagic in general. I've noticed that urban and rural kestrels in my area bring far more native birds to the nest than do those in more pristine habitats. In 1992 I saw a suburban falcon kestrel nail an adult Mourning Dove in the air, and have since seen the same thing documented photographically several times. Such an act would have been unimaginable from the truly wild, grasshopper and vole-eating kestrels I grew up with.
Commensal birds also displace natives, and are roundly vilified for it. Much is made of the effect English Sparrows and Common Starlings have on cavity-nesting birds, most notably bluebirds (Sialia spp.), whose nests they often appropriate. Of course, this only happens in habitats that have already been severely altered by human development, so it's a little disingenuous to blame the birds for continuing our own effect. The best way to conserve native birds is to leave their habitat alone in the first place. Like all our other commensals, the Spug will be a part of us for the foreseeable future, and I, for one, am happy to have him along for the ride. On this World Sparrow Day, let's all drink a toast to the health of the Party Birds!

Tuesday, November 27, 2018


Over the four-day Thanksgiving weekend, something like a dozen outdoor murals in Salt Lake City were vandalized. Some murals were on the walls of commercial businesses, others were decidedly non-commercial, like this wall, belonging to The Bicycle Collective, a great non-profit organization that provides low-cost bicycles and bicycle parts to the community, as well as a shop where people can work on their bikes. Also attacked were some murals that were created this summer during “Mural Fest,” a public art event spearheaded by another cherished local nonprofit, the Utah Arts Alliance, in collaboration with the City of South Salt Lake. My personal favorite damaged public art is on the wall of a former art gallery. It features copies of famous artworks with the main figure missing, so you can photograph your friend posing appropriately as the subject. Included are Whistler's Mother, Munch's “The Scream,” Boticelli's “The Birth of Venus” and others (below).

Judging from the styles, the spray-paint vandalism represented the handiwork of multiple people, but most of it looked like the top photo, with a crudely-drawn pizza slice, a spray can, a cartoon face (not shown in this photo) and the intials “TMB,” which I'm assuming stands for “The Mural Bomber.”

For years, graffiti artists have worked under an ethic that respects the work of others and eschews the defacing of pre-existing artwork. While I was working on a mural this summer, some local taggers left us this note one night on a section of wall we hadn't yet painted: "Howdy! Nice Mural!"

 In the rare event that murals have been vandalized, the motives have usually been clear and political, like the mural below, a celebration of early-20th Century Union Organizer Joe Hill, which was defaced by right-wing vandals in 2015, less than two weeks after its creation.

 The organized effort of last weekend is something new that has also recently been seen in at least a couple of other American cities. Unlike traditional guerrilla art, mural bombing has little thought or vision behind it. It's a revolution of dilettantes. I've heard some in the local art community describe these bombings as a counterattack against a cultural appropriation. They say that public art involving an exchange of currency treads on the territory of the street artists, and such a backlash is to be expected. It's likely that this accurately describes the motivation of these attacks, but to give these vandals credit for being the voice of street art culture is ridiculous. They're nothing of the kind. They're the whine of a petulant little club of amateurs.

Derek Dyer, the director of the Utah Arts Alliance, has started a gofundme page to raise funds for the restoration of these murals.

Monday, January 08, 2018


Hibernation is one of the more effective strategies temperate animals have developed to survive winter's cold temperatures and lack of food resources. Many birds, bats and even insects opt instead for seasonal migration, exploiting distant habitats during different seasons. A few, like the Monarch Butterfly (Danaus plexippus) and the Poorwill (Phalaenoptilus nuttallii) use a combination of the two. Poorwills, relatives of Nightjars, breed in arid parts of western North America from southern Canada into northern Mexico; northern individuals seem to winter in the desert southwest. A number of bird species use daily torpor to minimize energy loss during cool nights or brief bad weather. Members of three related orders, the goatsuckers, hummingbirds and possibly the swifts, all show some abilities at metabolic adjustment, but none to the degree of the little Poorwill, which, in addition to its natural tendencies toward torpor, feeds heavily on beetles, rich in polyunsaturated fats, which remain liquid and metabolically available at low temperatures. In the laboratory, Poorwills have been observed sustaining periods of torpor for over 80 days, and in the wild as long as 25 days.

A shallow shelter, open to the southern sun is selected: a patch of cactus or rock niche to which the bird develops substantial fidelity. After sundown, the torpid Poorwill's body temperature begins to fall, until the ambient temperature reaches 5.5°C, an apparent optimum hibernating level which the bird tries to maintain. Solar radiation raises the body temperature daily, presumably allowing the option to forage during warm nights. I know of no human witnesses to a Poorwill rousing from torpor in the wild, but I imagine the bird backing out of his shelter to fully bask in the final evening rays, periodically flapping his wings to elevate his body temperature. It's not known how severe a winter these birds can survive, but a sufficient winter insect population, rather than temperature, is probably the limiting factor.

upper: REANIMATION: COMMON POORWILL (2012) acrylic on illustration board 30" x 20"
lower: Field sketches of a female Poorwill feeding on darkling beetles, Salt Lake Co., UT June 2014

Sunday, October 22, 2017


In honor of National Reptile Awareness Day, I'm recycling this old post, "A SERPENT'S TAIL," from January of 2008:

Those of us from certain parts of North America tend to take rattlesnakes for granted, rarely bothering to appreciate how fantastic they really are. They comprise about 50 species, in two unique American pitviper genera, all with tails that are tipped with a series of complex, interlocking, cornified scales, completely unlike anything else known to have been evolved by snakes—until very recently, anyway. These reptiles are not only specialized at their very tips; the musculature of the tail itself is dominated by three pairs of “shaker” muscles, two of which produce lateral, back-and-forth movements, while the third pair applies torsion, drawing the ventral edge of the rattle outward to either side. The fibers of these muscles are rich in mitochondria, sarcoplasmic reticula, capillaries and glycogen, and capable of sustaining the high respiratory levels necessary to vibrate the tail as rapidly as 100 Hz. for as long as an hour at a time. These speeds are comparable to the oscillations of sphingid moth wings. Among vertebrates, only the hummingbirds (family Trochilidae) can vie with the rattlesnakes in this respect.The rattling system's main function is to warn away dangerous animals like predators and large grazing animals, although in some of the small Sistrurus species, it is only audible at close range, and appears to be of little use in this area. I've never witnessed a wild ungulate or carnivore interacting with a rattlesnake, but have many times seen how effective rattling is in deterring domestic analogs like dogs and horses. Whatever the first proto-rattlers used their tails for, they probably enhanced an already existent behavior. Similar tail movements are exhibited in snakes of many species, in many unrelated taxa. Tail-thrashing of various forms can be a prelude to battle or mating, or a means of evading predators. Some fossorial boids like Calabar Pythons (Charina=Calabaria reinhardtii) and Rubber Boas (C. bottae) wave their blunt tails about while hiding their heads (see photograph here). Some elapids, like the Langsdorff's Coralsnake (Micrurus langsdorffii) pictured above, confuse the enemy by moving both ends simultaneously. Many snakes, including some vipers, vibrate the tail defensively. When doing so against dry vegetation, the resulting sound is not unlike a rattler's. Defensive tail-shaking colubrids, like the Common Racer (Coluber constrictor), lack the specialized tail musculature, and cannot sustain the motion more than several seconds, but the tail muscles of the Copperhead (Agkistrodon contortrix), a close cousin of the rattlesnake, have a significantly elevated respiratory capacity. The traditional view of rattler evolution posits that rattles evolved to enhance this behavior, and, since the earliest-known rattlesnake fossils were found in the American Great Plains, it's tempting to visualize the first rattler warding off vast bison herds like in the painting up top. Genetic mapping, though, strongly suggests that rattlesnakes first evolved in America's southeast, severely shaking this attractive theory.

A third form of tail movement is caudal luring (see video here), a not uncommon behavior in vipers and a number of another snake taxa. It is possible that the earliest rattlers drew potential prey within striking distance by writhing and twitching a simple rattling tail appendage. Caudal luring is practiced by some of the earlier mentioned Sistrurus rattlesnakes, particularly the young ones; in fact, in many of the Crotalus spp. as well, the rattle could function more as a caudal lure in neonates, which can't produce sounds until their first shed. Concurrent with the young snakes' diet shift from ectotherms to mammals is the rattle's increased effectiveness as a sounding device, and the fading of bold colors and patterns on the tail. Both caudal luring and defensive tail-shaking are behaviors seen in the Copperhead.

A new species of viper sheds a bit of new light on the subject. Pseudocerastes urarachnoides was described just over a year ago, from two specimens collected in Iran (a pdf is available here). The holotype, an adult male (above, top), was collected in 1968 and deposited in Chicago's Field Museum. At the time, it was identified as a Persian Horned Viper (P. persicus), but its tail bore a strange appendage resembling a small solifugid (below). This Linkwas assumed to be a tumor or other aberration, until a second specimen, a young male (above, lower), was collected in 2003.

The tails of both specimens were carefully examined, and confirmed to be normal and uninjured. The assumption is that these structures are caudal luring devices, although so far, nothing is known of the species' behavior, and caudal luring has not to my knowledge been observed in the other two Pseudocerastes spp (--update--a video of the tail appendage can be seen here. The stomach of the paratype contains a partially digested, unidentified passerine bird. Latifi's Snakes of Iran lists P. persicus' diet as consisting of mice and lizards. Since the female P. urarachnoides is unknown, it's anybody's guess whether or not this tail appendage is a sexual characteristic. Both specimens were preserved in formalin, and their tissues were deemed to be unsuitable for molecular analysis. We can only hope that live specimens will be found and observed. If these hopes are realized, surely they will give us insight into the evolution of their distant cousins on the other side of the northern hemisphere, as well as into the nature of all life.
upper: PRAIRIE SENTINEL--PRAIRIE RATTLESNAKE (2002) acrylic 40" x 15"
lower two: Photos of P. urarachnoides taken from BOSTANCHI et al : NEW SPECIES OF PSEUDOCERASTES FROM IRAN. Proceedings of the California Academy of Sciences, ser 4, 57(14): 443-450 figs 1-4, 8-9