By Richard Telford
Author’s Note: This is the first in what I anticipate being a long series of posts on the natural history and conservation of vultures. While these posts will likely not follow a rigid order, I hope to eventually meld them into a longer, more substantive work titled In Defense of Vultures.
A light, easterly breeze bent the slender stalks of Queen Anne’s lace and goldenrod that had emerged in early summer from the patchwork quilt of little barley and fescue, overtaking red clover and thistle long past their blooming. Just as the breeze undulated the complex fabric of disturbance obligate plants, so too did life itself undulate there, in short, complex cycles in which plant overtook plant, each bringing an equally complex host of pollinators, predators, migrants, and breeders, all quickly mortal in the short-lived life-burst of the summer pasture.
Such were the observations I recorded on July 22, 2012 as I sat on Lois Cole’s small memorial bench nestled among the trees in Monument Pasture in the Edwin Way Teale Memorial Sanctuary in Hampton, Connecticut. By 1:30 the temperature had reached 80 degrees, and I sat adding species to a master site list while the raucous pasture music in all its forms reached its daily crescendo. Ten minutes later, a shadow at the periphery of my downward gaze drew it upward, first to the brightly lit mass of an old eastern white pine at the pasture’s southeast edge, then across the pasture itself, finally up to the azure sky marked by a scattering of cumulus clouds.
Perhaps thirty feet above, the penumbral form of a turkey vulture (Cathartes aura) drifted in its rocking, dihedral flight, circling the pasture several times before disappearing beyond the tree line. This dihedral flight, in which vultures utilize thermal columns and expend little energy, allows them to outcompete facultative vertebrate scavengers. This evolutionary adaptation is critical for vultures, the only known terrestrial vertebrate obligate scavengers, and thus vultures serve a concomitantly unique systemic role. Vultures increase the energy cycling of natural systems, moving energy stored in carrion quickly through the trophic levels. They likewise serve a critical sanitation function. Despite historic, cultural maligning of vultures as filthy scavengers that spread disease, they in fact check the spread of carrion-based diseases, aided by a number of evolutionary adaptations. These include exceptionally caustic stomach acid that can break down bacterially toxic carrion, featherless heads that resist the crusting of putrid flesh while feeding, and, in the case of the turkey vulture, acutely sensitive olfaction that will prompt rejection of the most toxic remains.
These and many other adaptations, some of which will be examined in subsequent posts, confer a unique ecological role upon the turkey vulture in particular and on the other 21 extant vulture species worldwide more broadly. Such niche roles necessarily create a duality for the species that fill them; while these species are especially critical to systemic function, they are also highly prone to extinction when the systems they occupy are disrupted. Such vulnerability is illustrated by precipitous population declines in the Gyps genus group in Asia and Africa, due principally to poisoning from livestock carcasses containing diclofenac, a commonly prescribed veterinary non-steroidal anti-inflammatory drug which causes rapid renal failure in exposed Gyps vultures. The Oriental white-backed vulture (Gyps bengalensis), for example, has suffered a staggering 99.9% population decline in India. These potentially catastrophic vulture losses will be examined more closely in a later post.
I focused little on the natural history or conservation of vultures on that warm July day. Instead, in my journal I noted the “low, lumbering flight, riding along warm air currents, still-winged and seemingly motionless.” The vulture was, I felt (and still feel), “an apt metaphor” for life, showing us the importance of “embracing life’s currents; changing direction by slow, deliberate degrees; conforming to the world’s parameters rather than trying to force the world to conform to our desired ones.” I concluded my observations by writing one simple word loaded with complex implications: “Magnificent.” Here was an illustration of the way in which scientific observation and emotional response cannot be fully separated, despite traditional calls for objectivity. In observing natural systems, how can we help but see ourselves, even if only through stark contrasts of what we may have been millennia ago, are at present, and may be in the future? Without such connections, how can we avert what Richard Leakey, Roger Lewin, Niles Eldredge, and others have termed the sixth extinction?
Five days after my initial turkey vulture observation at Monument Pasture, a shadow at the periphery of my gaze once again drew my attention. Driving home on state route 97, having finished a long morning of observations at Monument Pasture, a dark shape in the summer weeds at the road edge drew my gaze. A large wing rose up as I passed, and I could see the distinct, articulated wingtip feathers of a turkey vulture, likely car-struck. I pulled my car to the shoulder and walked heavy-heartedly back towards the vulture, its wings periodically unfurling, cutting the hot, dry air with the sound of delicate paper crumpling. I was distressed by the obvious suffering of an animal that, five days earlier, had evoked in me the deepest awe. I wondered if this could be the very animal that, days earlier, had silently circled Monument Pasture.
Reaching the vulture, I realized it was already dead; its bluish eyelid was drawn tight, a small heart-shaped pool of blood darkened the ground near its beak, its frame neither expanded nor contracted with breath. The light, broad wings that in life had allowed its effortless soaring now caught even the slightest breeze, drawing the splayed bird upward by inches only to drop it again like a downed kite. I quickly rough-sketched the vulture in its entirety, first feeling grief, then wonder, then gratitude. Realizing the gift of observation that this vulture had unwittingly given me through its death, I knelt beside it for another ninety minutes, painstakingly sketching its head, seeing the beauty of its graceful flight mirrored in the complex beauty of its functional adaptations. Gazing at this young vulture’s hooked, tearing beak, its bald head that would resist the caking of putrid flesh as feathers could not, its large, open nostril through which the ground beneath it was visible, it was clear to me why Thoreau, 158 years earlier in Walden, had written, “We are cheered when we observe the vulture feeding on the carrion which disgusts and disheartens us, and deriving health and strength from the repast.” If we wish to avert the sixth extinction, perhaps the beauty of function must be invoked to foster conservation-mindedness as readily as the beauty of form.