For no particular reason, here are some interesting raptor photos. Birds of many kinds often sit around with their wings only partially folded, partly hanging down at their sides; one reason for this is that they’re sun-bathing and are using their wings to soak up heat. Among raptors, this behaviour is well known for Turkey vultures Cathartes aura in particular. But many others do it, and here’s another New World vulture (cathartid), an Andean condor Vultur gryphus, doing the same thing [photo by Markus Bühler, taken at Berlin Zoo].
During cold weather, captive Andean condors are reported to mostly sit still, with their neck ruffs pulled up to the head. They expose the bare neck and naked breast patch in warmer weather. Occasionally, males kept with females will inflate their necks, at the same time changing the skin colour from pinkish-grey to “a distinct pale rose and sulfur yellow” (Gailey & Bolwig 1973, p. 60).
The condor’s pose shown above reminds me of the pose adopted by this Lappet-faced vulture Torgos tracheliotos, photographed in captivity (I think in London Zoo) many decades ago.
I’ve used this photo before (in my review of Kaiser’s The Inner Bird) because – one might argue – the pose helps remind people that a bird’s wing is merely a tightly folded version of the maniraptoran arm. Anyway, I’ve always wondered why this bird was holding its wings like this: sun-bathing doesn’t look likely on this occasion. Was the bird merely photographed in the act of folding its wings up, or was there something wrong with it? Torgos is an Old World vulture (an aegypiine accipitrid), apparently closely related to the Black or Cinereous vulture Aegypius monachus and the White-headed vulture Trigonoceps occipitalis (Lerner & Mindell 2005). The large size (wingspan up to 2.7 m) and robust bill of Torgos mean that it is dominant to other Afro-Arabian vultures at kills.
And while on the subject of aegypiine vultures…
This is the head of a griffon vulture (griffons: the eight or so Gyps species): I assume (based on the pale bill, straw-coloured iris and pale head and neck) that it’s a G. fulvus (typically just called the Griffon vulture) [photo by Markus Bühler, taken at Berlin Zoo]. It serves to remind us well that most Old World vultures aren’t ‘naked headed’ at all: they actually have a very respectable covering of fine, filamentous feathers. In fact, Torgos is the peculiar one in being naked-skinned. Rather than being anything to do with keeping clean at carcasses (the most usually proposed function for naked-skinned heads and necks), the peculiar head and neck feathering of griffons might be more to do with thermoregulation: these birds have to cope with rapid temperature fluctuations of as much as 70° C (Ward et al. 2008) as they move rapidly from soaring in cold, high-altitude air to running around on the hot ground in tropical environments. I’ve had some nice encounters with griffons in Spain, check out these photos (courtesy of Bob Loveridge)…
One really important point that needs emphasis whenever vultures (both Old and New World) are discussed is that they most emphatically are not sorry, garbage-eating consumers of leftovers. While it’s – of course – true that they eat carrion, vultures are the primary consumers of this enormous resource, out-competing all other carrion-feeders simply by finding and consuming carcasses more rapidly than anything else (DeVault et al. 2003). Lord Geekington covered vultures back in 2009 (sorry, Cameron) and wrote “So forget the image of vultures cleaning up after lions on the savannah – they consume staggering amounts of biomass from carcasses the size of mice to elephants in temperate and tropical environments worldwide (except Australia…)”.
Condors and their possible close relatives, teratorns, were previously covered here…
And for more on raptors of all kinds, see…
- Yet again, poor little deer gets killed by big nasty eagle
- Titan-hawks and other super-raptors
- The most amazing eagle footage ever….. faked
- Raptor makes killing in university grounds
- When eagles go bad, all over again
- Screwed-up Secretary bird
Refs – -
DeVault, T., Rhodes, Jr., O., & Shivik, J. (2003). Scavenging by vertebrates: behavioral, ecological, and evolutionary perspectives on an important energy transfer pathway in terrestrial ecosystems Oikos, 102 (2), 225-234 DOI: 10.1034/j.1600-0706.2003.12378.x
Gailey, J. & Bolwig, N. 1973. Observations on the behavior of the Andean condor (Vultur gryphus). The Condor 75, 60-68.
Lerner, H. R. L. & Mindell, D. P. 2005. Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Molecular Phylogenetics and Evolution 37, 327-346.
Ward, J., McCafferty, D. J., Houston, D. C. & Ruxton, G. D. 2008. Why do vultures have bald heads? The role of postural adjustment and bare skin areas in thermoregulation. Journal of Thermal Biology 33, 168-173.