Appreciating the Cleanup Crew

October 24, 2022 ~ I have fallen into a bad habit, judging a bird by its cartoons, instead of by its real nature and place in its ecosystem. When a vulture circled overhead, I typically took a few cursory shots (because, practice), but without really looking or learning. So, as Halloween approaches, it seemed a good time to focus on some overlooked birds.

Range maps for Black Vultures (left) and Turkey Vultures (right), courtesy of All About Birds

There are two distinct populations of vultures on the planet, the Old World Vultures of Europe, Africa and Asia, and the New World Vultures of North and South America. These populations are genetically separate, suggesting that two different branches evolved at the same time, filling similar ecological niches, resulting in similar body plans. In North America, there are three species of vulture, the Black Vulture with approximately 190 million birds globally, the Turkey Vulture, with roughly 28 million birds globally, and the California Condor, just barely rescued from extinction with around 500 birds located only in a tiny area along the US west coast. The Black Vulture is sometimes called the American Black Vulture, perhaps for linguistic symmetry in differentiating from the Eurasian Black Vulture, one of the Old Word Vultures.

Black Vulture displaying silvery wing-tips during a long glide
1/1600 sec. f/5.6 ISO 2000
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR
(Click on any photo once to enlarge in a new window; close that window to return here.)

The Black Vulture, Coragyps atratus, is almost completely black. He has “jazz hands”: the tips of both the upper and lower wing surfaces have a silvery pewter coloring that looks gray in some lights, and bright white in others. The Black Vulture has black skin, including his naked head and neck, and a black bill. Black Vultures are scavengers, but have been known to attack and eat live prey that were sick, injured or newborn. Their scientific Family name, Cathartes, is the Greek word for “purifier,” referring to vultures’ role as “cleaners”, removing decomposing corpses in nature.

Turkey Vulture displaying under-wing silvery stripe
1/2000 sec. f/7.1 ISO 2500
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

Black Vultures often travel with the Turkey Vulture, Cathartes aura, which is mostly black with distinctive silvery pewter bands under the full length of their wings’ trailing edges. Turkey Vulture head and neck are naked and both head and bill are reddish in color. And the Turkey Vulture wobbles as he soars, while the Black Vulture has a steady flat-winged soaring path. This Turkey Vulture kept flying from one fence post to another, advancing along the road as I slowly drove along taking his picture, at Anahuac National Wildlife Refuge.

Black Vultures canoodling
1/2500 sec. f/5.6 ISO 1600
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

Black Vultures mate for life, and pairs can often be seen snuggled together on a sturdy roosting branch. This pair cuddled up in late afternoon, at Aransas National Wildlife Refuge, near Rockport, TX. They didn’t just sit side by side, they nuzzled each other’s shoulder, edged their feet over on the branch so that their sides were touching, gently touched bills and grunted softly to each other. It is an unfortunate reality that the mate of a Black Vulture killed by a vehicle on the road, will often also be killed, as the mate is reluctant to leave their dead partner.

Juvenile Black Vulture with feathered head
1/1600 sec. f/7.1 ISO 2000
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

This is a juvenile Black Vulture, his head covered by little-guy short black feathers, which have not yet transitioned to the mature bird’s wrinkled featherless head and neck skin. This juvenile was sitting by his older sibling on a bridge railing at Creekside Lake, in Brazos Bend State Park, near Houston TX.

Immature Black Vulture sibling
1/1600 sec. f/7.1 ISO 2500
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

His sibling’s cowl of wrinkled skin has developed around his face, giving him a raised-eyebrows look, but his head and neck are still feathered. Black Vultures reach breeding age when they are 3 – 5 years old, so I’m guessing this might be a second-year bird. The Black Vulture family is a tightly bonded social group. The parents stay close to the young birds, and continue to feed them occasionally, months after the youngsters are able to fly and hunt on their own. Family groups of multiple generations stay together, and will defend a carcass from non-family Black Vultures.

Black Vulture (perhaps second-year) prying under park bridge tag
1/1600 sec. f/7.1 ISO 2000
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

The Black Vulture’s bill is well-adapted to the tearing action needed to remove meat from bones. This action is a core behavior; large gatherings of vultures can become pests, tearing at roof shingles, window calking, and vinyl seats on boats, motorcycles, golf carts and more. I thought this young adult was intent on fishing some tasty snack out from under the metal label but he may also have been simply picking, for a reason known only to vultures.

Mature Black Vulture watching over family dinner
1/2500 sec. f/5.6 ISO 800
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

This is the quintessential Black Vulture pose – one bird per pole, for two to five poles in a row. Often it appears that one is lookout, while the rest of the family feeds. This one was posted on Davis Estates Road south of Brazos Bend State Park, while a group of 5 more birds cooperated to make short work of some road-kill they had pulled from the road to the ditch.

Black Vultures locate their prey by sight, not by smell. They often circle above a kettle of Turkey Vultures, which have a highly developed sense of smell. When the Turkey Vultures locate prey and drop to the ground, the Black Vultures follow them to the carcass, where they take possession, aggressively defending against the Turkey Vultures. It is interesting to note how the Black Vulture range is almost entirely enclosed within the Turkey Vulture range; the former is quite dependent upon the latter to find food.

This tidbit comes from All About Birds:

Researchers proved fairly long ago that Turkey Vultures can smell. In 1938, the Union Oil Company discovered that by injecting a strong-smelling organic chemical called mercaptan into gas lines, they could readily find leaks by monitoring vulture activity above the pipelines. Some mercaptans smell like rotting cabbage or eggs. They and related chemicals are released as carcasses decompose. To us, mercaptans smell horrible, but for [turkey] vultures they are associated with fine dining.

Mature Black Vulture
1/2500 sec. f/5.6 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

This member of their group did a two-step flying hop across the road in front of my car to the long grass opposite. Vulture feet are good at walking or hopping, but are not strong enough for crushing or ripping, like hawk or falcon feet. Instead, vultures land directly on or in a carcass, stabilizing their food and bracing their bodies with their feet while tearing with their bill. Rolling the windows down to photograph this family treated me to the aroma of their repast, and was an eye-watering reminder of their special niche in our environment.

Vultures have evolved extremely powerful stomach acids and gut bacteria, which kill the germs they ingest with their over-ripe dinners (e.g., rabies, anthrax, botulism and salmonella). And, you recall I said their skin is black… but when you look at the photos, you’ll see white legs. Are you ready? Vultures poop on their own legs and feet. On purpose. Many references say they do this to cool their legs and feet, a behavior called urohydrosis documented in several species, including storks. I wonder if an added benefit is to disinfect their legs and feet with the same acid bath that kills the deadly bacteria in their stomachs.

Please approach the bench
1/2500 sec. f/9 ISO 1600
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

It is not just the black satin plumage and knurled head and neck cowl that evokes the image of a be-wigged judge sitting in somber judgement. On two separate occasions, I watched as a vulture sat hunched over, gazing at me with quiet and unmoved regard, and then deliberately lifted just one or two toes of one foot and carefully placed them down again. It was as if they were pensively tapping one finger on their massive desk, while deliberating my fate.

But that was just the cartoons talking. Today, I am amazed again at the variety of solutions nature has evolved for living in every niche imaginable, and I’m thankful for the cleanup crew.