March Nature Almanac: Soaring Into Spring on a Turkey Vulture’s Wing
By Ruth Carol Cushman, with Stephen R. Jones and Scott Severs
March 2024
A hulking black bird associated with carrion is not what most people think of as a harbinger of spring. Nevertheless, the return of Turkey Vultures from Mexico, Venezuela, and points south brings excitement to winter-weary Colorado birders. “TVs”, as aficionados say, or Cathartes aura, as scientists say, soar into Boulder County by early April, riding thermals of warm air to attain great heights with little effort.
Is this turkey vulture giving the photographer a quizzical look or an evil eye? Photo by Stephen R. Jones.
With wings uplifted in a dihedral, or V-formation, and tilting side to side in the wind, Turkey Vultures look as though they indulged in too many Bloody Marys. The birds are such proficient fliers that the Wright brothers designed their first airplane based partly on the Turkey Vulture's skill of adjusting feathers to control the flow of wind over their nearly six-foot wide wings.
Graceful in the sky but ungainly on the ground, these nearly eagle-sized birds hop clumsily around dead animals or sit hunched in trees as though their two-foot-plus height were too much for them. With a scrawny, featherless red head Turkey Vultures are not pretty close up, and some of their habits could be considered gross. The lack of head feathers lessens the mess when they thrust their heads into the entrails of a bloody carcass. They defecate on their legs to cool off AND they use projectile vomiting as a defense weapon.
A single turkey vulture in the Boulder roost. Photo by Stephen R. Jones.
A strong sense of smell and keen eyesight help them find carcasses far below. They also watch for other vultures circling above a dead animal. So, if you see a few together in the sky, you may soon see dozens—an aggregation referred to as a “kettle.” Other collective nouns for these sociable birds include "cast," “venue”, "committee," "vortex," and "wake." We propose “olfactory.”
Roadkill is a popular menu item. Their feet, however, are too weak to carry large chunks of food, so they tend to hunker down by the road to dine, often becoming roadkill themselves. They are seldom deliberately persecuted, as most people are grateful for the clean-up crew. In fact, their genus name, Cathartes, means purifier.
A turkey vulture spreads its wings to dry in the early morning light. Photo by Stephen R. Jones.
When populations of nine species of Old World vultures plummeted in India in the mid-1990s, the human deaths rose alarmingly. According to a recent article in The Economist, human mortality rate rose by 4% in districts where vultures no longer demolished carcasses. Rotting flesh led to an increase in deadly pathogens in the water and to an increase in feral dogs and rats, which carried rabies and other diseases. It’s estimated that an additional 500,000 human deaths occurred when vultures disappeared.
The contributing culprit of the population decline turned out to be diclofenac, an anti-inflammatory drug commonly used to treat cattle, but highly toxic to vultures who fed on cows that didn’t recover. When diclofenac was phased out starting in 2006, the nine vulture species (only distantly related to New World vultures) slowly began to recover. Several species, however, are still in danger of extinction.
In the US, California Condors are recovering from the brink of extinction after extensive captive-breeding efforts. Like the Indian vultures, one factor holding them back is a toxin in the carcasses they eat – lead shot. California banned lead shot in 2019. Arizona and Utah, other states where condors now live free, have not. The other two US vulture species—turkey and black—are thriving. Only the Turkey Vulture is common in Colorado.
Several Native American tribes call vultures “peace eagles” because they are the only bird that does not kill. While many people associate them with raptors, DNA studies show they are more closely related to storks, gulls, pelicans, and loons than to hawks and eagles.
Turkey Vultures reach breeding age at about five years old and mate for life. They perform aerial courtship displays in spring and often sit companionably side by side, but songsters they are not. They do little vocalizing except for hisses and grunts.
Females start laying eggs in April, but their nests are notoriously difficult to find as the birds favor crevices and caves for nesting. The secretive parents will not approach the nest if they see a person within a mile or so of it. The adults also leave to hunt during the day, not returning until evening when they regurgitate food to their young. The aroma of vomited carrion is often the only clue to locating a nest. In 130 years, fewer than half a dozen nests have been documented in Boulder County.
An “wake” of turkey vultures in a Nebraska roost tree. Photo by Stephen R. Jones.
Roosts where large numbers of unmated birds spend the night are easier to see. We have watched some thirty juveniles fly out of the large maples along 6th Street below Flagstaff Road in Boulder at sunrise. The largest recorded roosts are in Florida where 4,000 vultures have been counted at Lake Okeechobee in winter.
A good place to see migrating Turkey Vultures and other raptors is the Dinosaur Ridge Hawk Watch north of Morrison. From I-70 take exit 259, park at the south Point of Geologic Interest, and hike the trail to the ridgetop.
Former Boulderite and wildlife specialist Christina Nealson will lead the Arivaca Vulture Fest in Arivaca, Arizona, from March 22-23, 2024. Participants will dance, sing, wax poetic, and watch the vultures return to their roost tree at night. Many similar festivals are held around the southwest to welcome the vultures back, and on the first Saturday in September International Vulture Awareness Day is celebrated around the world.
Other March Events
The earliest breeding birds are starting to incubate or even have nestlings.
NestWatch, a nationwide nest monitoring program run by Cornell, reported a couple of early hatchlings of Eurasian Collared-Doves (2 min video), born in Berthoud, Colorado, on January 21.
Bald Eagles are incubating eggs. Nest monitors at Stearns Lake say this is the earliest incubation since they have been keeping records there.
Folks at the February BCAS Audubon meeting reported seeing the first American White Pelicans and Mountain Bluebirds of the spring. Sandhill Cranes should soon be winging and trumpeting overhead.
Easter daisies begin blooming on shales adjacent to the Foothills Highway north of Boulder in early March, and spring beauties and pasqueflowers usually bloom in the foothills by month’s end.