The Ecological Value of Turkey Vultures (Cathartes aura)

In late May 2015 I was able to capture some good photos of a pair of turkey vultures (Cathartes aura) feeding upon a rabbit carcass. These are very interesting birds, despite their questionable reputation garnered by their lifestyle of feeding upon carrion. While humans might find this disgusting, this is actually a very important ecological function since it means that decaying animals are quickly removed from the scene, which helps prevent the spread of diseases. It also stops the breeding of flies and other undesirable pests in decaying carcasses. The generic name of Cathartes means “purification” and pays homage to this trait.

vultures eating rabbit carcass near bedroom window,Th May28,2015 105Turkey vultures are the primary avian scavengers in North America, and are found over all of the contiguous 48 states and into southern Canada in summer. They migrate southwards in winter and are permanent residents in the southern states, Mexico, and South America.

vultures eating rabbit carcass near bedroom window,Th May28,2015 172Turkey vultures have almost no natural predators, but when they do feel threatened they have a nasty tendency to vomit up partially digested, decaying meat onto their aggressors. This is more than enough to deter most would-be attackers. They lack a syrinx, which is the vocal organ of birds, and cannot utter any noises other than a few grunts and hisses. They are fairly large birds, with wingspans of about 5 to 6 feet (1.7 meters) and weighing about 4 to 4.5 pounds (2 kg) in North America. South American birds tend to be a bit smaller.

vultures eating rabbit carcass near bedroom window,Th May28,2015 263Turkey vulture nostrils are not separated by a septum, a condition called perforate, which means that you can see through the beak when the vulture is turned sideways. Unlike most birds, vultures have a very strong sense of smell, and are capable of detecting even tiny concentrations of ethyl mercaptan, which is the chemical we associate with the odor of decay in dead animals. That plus their keen eyesight enables them to find carcasses, even hidden in vegetation.

vultures eating rabbit carcass near bedroom window,Th May28,2015 228The naked, featherless head is an adaptation to keep somewhat cleaner when the birds probe into rotting carrion. Since having feathers on their heads would be a cleanliness issue (because birds cannot easily groom their own heads) they have simply dispensed with having them there at all. The dark red pigmentation helps them avoid UV sun damage. Vultures typically live 13 to 15 years in the wild, and captive birds have exceeded 30 years in age.

vultures eating rabbit carcass near bedroom window,Th May28,2015 135Note the white staining on the legs and feet of the vulture. They have a habit of urinating and defecating on their legs to help cool off on hot summer days, a process called urohydrosis. Vultures normally have pink skin on their legs otherwise.

They do not make good pets for this reason. 😉

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On Saturday June 8, 2019 as I was preparing to leave for a trip to San Diego in the early morning, I stepped outside to commence loading the car with items I was taking with me. A turkey vulture flew off from a Joshua tree about 100 feet away down my driveway, drawing my attention. Another vulture remained sitting upon a Baja cardon cactus (Pachycereus pringlei) that is adjacent to the cardon, and graciously stayed put for the next few minutes while I obtained my camera and took a series of photos of it from various angles. The following pics are from that session.

P1590941 (2)The first photos I took were of the vulture sitting on the cardon, framed nicely by a Parry century plant (Agave parryi) in full, prime bloom. The perspective is a bit flattened due to the distance I was away but the agave is about 35 or 40 feet closer to me than the cardon and vulture are. You can see the more prominent ribs of the cardon which are nearly spineless, as opposed to the spiny, fuzzier look of the other cacti farther down the drive, which are all native saguaros (Carnegiea gigantea).

P1590961 (2)I wanted to grab these photos while I still could, partly because I could zoom in on the agave from this perspective, and also because I didn’t know if the vulture would tolerate a closer approach. Better to get at least some images up front in case the bird got spooked away as I attempted to draw nearer.

P1590968 (2)The vulture was not alarmed by me as I got closer, although I made it a point to move slowly and avoid eye contact as I did, so as to avoid seeming like a threat. The vulture rewarded my caution by opening its wings and doing a bit of early morning sun basking. This is a frequently seen behavior of vultures in the early mornings as they use solar energy to help warm themselves up.

P1590971 (2)A nice detail shot of the vulture in sunbathing mode. I was perhaps about 60 to 70 feet away at this point, using the zoom lens in motor drive mode to catch photos in rapid fire succession. I like how you can again see the perforate septum in the nostrils as light shines through.

P1590973 (2)The bird folds its wings, but remains in place as I move around. My goal was to try to make a wide circle around the perching spot and get the combination from the opposite direction, not in backlighting mode.

P1590997 (2)I made a broad circuit around the vulture, who kept an eye on me but clearly did not seem frightened by my presence. Eventually I moved east of the bird and got the morning sun on it directly. The Parry agave bloom spike in the first photos is now a backdrop. Also see the differences in the stems of cardons versus saguaros in terms of epidermal colors and spination. The two plants are easy to confuse, but an experienced observer can readily tell them apart based upon appearance even at a distance.

P1590979 (2)A cropped-in detail shot of the vulture showing the striking red skin of the featherless head.

P1590988 (2)The bird flapped its wings again. It decided to fly off a short time after this, which didn’t disappoint me since by this time I had snapped over 100 photos of it.

P1590989 (2)Final shot of the vulture spreading its wings just before takeoff.

starving cows, almost new moon sunrise,Urginea fl Fri-Sat Sep7-8 032Here is a different photo taken in September 2018 of a flock of vultures perching on a couple of Joshua trees a few miles away from my house and garden. These birds were feeding upon a dead cow carcass that had died from starvation in the dry year between September 2017 and October 2018 that had preceded this photo. I posted about the starving cattle back then – you can read the story here:

A Discussion of Cattle and Drought Starvation (Warning: Sad Images Within)

starving cows, almost new moon sunrise,Urginea fl Fri-Sat Sep7-8 037A vulture at the dead cow carcass. Vultures are semi-social, in that they often congregate in groups to feed or rest, and rely upon a community of eyes and nostrils to find their carrion food. But they frequently travel alone as well and nesting behavior is usually solitary, not communal like some birds.

Pinacate 4 drive PP-PLib,LunarEcl SuperWolfBlood,cardonsSunJan20 1537 (2)A final shot from January 2019 taken down along the coast of Sonora, Mexico on a wildflower and lunar eclipse trip I took down there a few months ago. The flock is resting in a cardon grove, again displaying the communal behavior that they commonly do. For an account of the “Super Blood Wolf Moon” lunar eclipse in the nearby cardon forest, visit this blog post here:

Lunar Eclipse In A Mexican Cactus Forest

Thanks for reading!

 

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