The Andean condor: a bird that hardly ever flaps its wings

The Andean Condor (Vultur gryphus) is a bird with one of the longest wingspans in the world—about 3.3 meters, or 10 feet 10 inches. Their mean weight is 11.3 kg (25 lb), with males weighing about a kg more than females. Wikipedia notes that its wingspan is “exceeded only by the wingspans of four seabirds and water birds—the roughly 3.5 m (11 ft 6 in) maximum of the wandering albatross, southern royal albatross, great white pelican and Dalmatian pelican”.

The condor is a denizen of the Andes and a carrion eater, now favoring large dead animals like cows and cattle, though before humans arrived it certainly feasted on the carcasses of native herbivores like guanacos.

A new paper in PNAS (see below) gives data obtained by affixing electronic devices to eight condors, devices that recorded their altitude, whether they flapped their wings (measured by an accelerometer), and how far they traveled using an included GPS. The results are quite amazing: they hardly every flap their wings except when taking off. But I am getting ahead of myself. First, have a look at the soaring behavior of this bird in a 2½-minute video. You can see one desultory wing flap 36 seconds in, and another at 2:20. That’s it.

 

You can read the PNAS paper for free by clicking on the screenshot below; the pdf is here, and full reference at bottom.

And, at The Conversation, one of the authors, Emily Shepard, describes the study in layperson’s terms (click on screenshot).

The authors caught juvenile condors by luring them down with sheep carcasses, and than affixing clever electronic boxes to the birds, boxes that were designed to fall off after a few days when they were roosting. The data collected was so copious—320 pieces per second, that they couldn’t record it in real time, but had to recover the boxes from the roosting sites and download the data that way.

Here’s a bird being tagged (two photos below from The Conversation piece)

And retrieval of the data box:

The results are unsurprising in one sense, as they found (and we already knew) that these birds soar by using thermals—warm rising air—as well as winds blown upwards when they contact mountain peaks (updrafts).  But the surprising thing was how rarely the condors flapped when they were on their foraging flights.

In 235 hours of flight time recorded (1.3 billion data points!), the authors found that condors spend about three hours of the day soaring between roosting and feeding sites, looking for livestock carcasses.  The intriguing result was how little wing flapping there was: only about 1% of that time aloft was spent flapping.  One striking bit of data came from a single bird who didn’t flap its wings at all for 317 minutes (5 hours, 17 minutes), and yet covered 172 km (107 miles).

This is the lowest amount of flapping of any free-ranging bird, and of course this reduces the energy needed to keep such a large bird aloft. In toto, researchers calculated that 21% of the daily costs of flight were spent in flapping while aloft, while 75% of the costs were involved in takeoff, each such takeoff using the energy equivalent of 3.3 minutes of flapping. Takeoff is onerous, time-consuming, and dangerous, as, say the authors, condors are susceptible to predation then (presumably by large cats like pumas).

Here’s a 25-minute readout from a single soaring condor giving three bits of information: the altitude (top), the heading (middle), and whether they were flapping (“acc” or acceleration), bottom. There appear to have been seven or eight flaps.

The extremely low rate of flapping, using only about 1% of its time aloft, and the bird’s use of thermals and updrafts, explains how such a heavy bird can maintain its lifestyle without expending excessive energy. And the high costs of takeoff explain (along with predation) why these birds roost and nest on high mountain ledges, where they don’t really have to take off, but can simply fall off the ledge and begin soaring.

What are the implications of this work? The authors mention an extinct terrestrial bird, Argentavis magnificens, which apparently weighed about 72 kg—more than six times heavier than the Andean condor. (It’s know from a single humerus, or upper arm bone, which is about as long as a human’s.) Here’s a photo of its size relative to humans and Andean condors:

 

Wikipedia gives details, and adds that there’s now a fossil species with an even longer wingspan one that would extend to the right side of the figure above!:

Argentavis wingspan estimates varied widely depending on the method used for scaling, i.e. regression analyses or comparisons with the California condor. At one time, wingspans have been published for the species up to 7.5 to 8 m (24 ft 7 in to 26 ft 3 in) but more recent estimates put the wingspan more likely in the range of 5.09 to 6.5 m (16 ft 8 in to 21 ft 4 in). Whether this span could have reached 7 m (23 ft 0 in) appears uncertain per modern authorities. At the time of description, Argentavis was the largest winged bird known to exist but is now known to have been exceeded by another extinct species, Pelagornis sandersi, was described in 2014 as having a typical wingspan of 7 to 7.4 m (23 ft 0 in to 24 ft 3 in). Argentavis had an estimated height when standing on the ground that was roughly equivalent to that of a person, at 1.5 to 1.8 m (4 ft 11 in to 5 ft 11 in), furthermore its total length (from bill tip to tail tip) was approximately 3.5 m (11 ft 6 in).

Argentavis was certainly airborne, and the present work on condors shows that it probably remained aloft by soaring. That, in turn, would imply that it was a scavenger and not a predator, as the latter lifestyle would imply a much more active flight that would be impossible in such a bird. I’ve seen an Andean condor once, in Argentina, and even though it was way up in the sky, it was still impressive. Imagine what it would look like to see an Argentavis magnificens soar past!

____________

H. J. WilliamsE. L. C. ShepardMark D. HoltonP. A. E. AlarcónR. P. WilsonS. A. Lambertucci. 2020. Physical limits of flight performance in the heaviest soaring bird.

20 Comments

  1. Ken Kukec
    Posted July 16, 2020 at 9:05 am | Permalink

    Never knew until just now that the soundtrack tune to that vid, Simon & Garfunkel’s “If I Could,” is known in Spanish as “El Condor Pasa.”

    • Jonathan Wallace
      Posted July 16, 2020 at 10:17 am | Permalink

      I believe Simon and Garfunkel use the name ‘El Condor Pasa (If I could)’ on their track lists. It is a Peruvian melody that they covered.

      • Ken Kukec
        Posted July 16, 2020 at 11:52 am | Permalink

        Thanks. Having flaunted my ignorance in this manner, I can empathize with why they’d rather be a hammer than a nail. 🙂

        • Jonathan Wallace
          Posted July 16, 2020 at 12:30 pm | Permalink

          🙂

  2. Bill Shipley
    Posted July 16, 2020 at 9:11 am | Permalink

    The idea that, by using allometric scaling, one can deduce so much about the ecology of extinct organisms, is fascinating. I wonder if anyone has tried to recreate an entire ancient ecosystem, covering all of the fossil organisms found, using this method?

  3. Sher
    Posted July 16, 2020 at 9:26 am | Permalink

    As someone who does research on condors, I love that your return to reporting science papers (no criticism intended–I read that post) is a great new paper on the most fascinating bird in the world.

    –Totally Biased.

  4. ThyroidPlanet
    Posted July 16, 2020 at 9:28 am | Permalink

    Awesome!

  5. notsecurelyanchored
    Posted July 16, 2020 at 9:37 am | Permalink

    Now I want to come back as a condor.

    • Jacques Hausser
      Posted July 16, 2020 at 9:54 am | Permalink

      Bon appétit!

      • Posted July 16, 2020 at 5:57 pm | Permalink

        To paraphrase Snoopy:
        I could never eat a rotting dead skunk on a hot August morning.

        • phoffman56
          Posted July 17, 2020 at 6:55 am | Permalink

          Lacking in culinary skills, was he?

  6. Randall Schenck
    Posted July 16, 2020 at 9:43 am | Permalink

    They make even the most high performance gliders look bad. The aircraft I worked on years ago, F-100 had the glide ratio of a rock. That is why it was called the lead sled.

    • bPer
      Posted July 18, 2020 at 11:05 pm | Permalink

      They make even the most high performance gliders look bad

      Sorry, Randall, not even close. According to this paper, the Andean condor has a glide ratio of 14:1. Even a basic training glider like the Schweizer SGS 2-33 blows that away, achieving 22:1. Typical standard class gliders are in the 40+ range, and open-class gliders achieve better than 60:1.

      BTW, if you follow that link to the 2-33, the picture at the top of the article shows a 2-33 with registration C-GRVS. That’s the actual plane that I soloed in! In the third picture, you can see it at the club (Rideau Valley Soaring, south of Kars, Ontario, Canada). In the background, you can see another of the club gliders, a Grob G103. It gets 36:1. A nice plane to fly.

      βPer

  7. phoffman56
    Posted July 16, 2020 at 9:50 am | Permalink

    Nothing like a perpetual motion machine, but can you imagine civilized highly scientific beings living on a planet whose atmosphere’s properties are such that virtually all their long distance travel comes from the energy of the wind applied directly to the wings of their flying machines. The condor people.

    Will humans ever make this a possibility? It certainly would be a big advance re climate change problems, but seems very unlikely soon enough.

    I really would like to visit the Andes sometime soon; and bring the old Simon&Garfunkel with me.

  8. Jonathan Wallace
    Posted July 16, 2020 at 10:27 am | Permalink

    Albatrosses also manage to cover huge distances with barely any wing-beats. Rather than using thermals they use a technique known as dynamic soaring that exploits gradients of wind-speeds over the ocean surface. https://jeb.biologists.org/content/221/1/jeb169938

    The different methods used to achieve efficient soaring account for the differences in wing shape with the condor having the very broad wings and albatrosses having long slender wings.

    • Posted July 16, 2020 at 6:12 pm | Permalink

      Very cool. Evolution works hard to give its organisms access to free energy!

  9. Posted July 16, 2020 at 11:27 am | Permalink

    It would have been amazing to see such a bird as Argentavis magnificens flying. Some of the pterosaurs were even larger, much larger. Wikipedia says Quetzalcoatlus northropi maxed out at 13m (43 ft)! This would make it over double the wingspan of Argentavis magnificens. Keep your small children under cover!

  10. Joseph McClain
    Posted July 16, 2020 at 3:11 pm | Permalink

    Very interesting. I spend a lot of time watching turkey vultures soar and I’ve always wanted to see an Andean condor.

  11. Posted July 16, 2020 at 3:36 pm | Permalink

    And how about ~250kg arkdarsid pterosaurs taking off?

    rz

  12. Mark R.
    Posted July 16, 2020 at 4:40 pm | Permalink

    An amazing bird. It’s sad that their population is decreasing. Hopefully a program like the one that has succeeded in increasing the California condor’s population can be implemented.


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