Protective Nesting Associations
and large falcons
sometimes nest near each other. Although falcons are smaller
in size than condors, they are better defenders of their nests. Consequently, when falcons aggressively drive away other predators from their nesting
territories, they also drive away predators from nearby condor nests, and
so can increase the chances that condor eggs and chicks survive
(Snyder & Snyder 2000).
In California, the Raven (Corvus corax)
is the main predator of condor eggs, while the Golden Eagle is the main predator of condor chicks
(Snyder & Snyder 2000).
One California Condor nesting territory was monitored for several years
and, during one year, it was found that at least 5 pairs of Prairie Falcons
nested "within a 2.4 kilometer radius of the territory center," driving
away most Ravens and Golden Eagles
that entered it (Snyder & Snyder 2000)
surprisingly, the condor egg and chick in this territory survived during
that nesting season. Two years later, however, prairie falcons nested
further away from the condor nest and consequently did not provide nest
defense for the condors. During that season, ravens invaded the territory
and nested near the condors. Not surprisingly, these ravens caused
"two successive nesting failures of the condors
(Snyder & Snyder 2000)
Of course, nesting near falcons is costly for the condors also, since
falcons aggressively dive at condors and cause them to waste time and
energy to avoid these attacks. However, the cost is well worth it to
the condors if eagles and ravens
threaten their nests (Snyder & Snyder 2000).
For more information about how birds increase
their breeding success by nesting near falcons and other birds of prey, see our
special review: Hawks, Owls and
Falcons that Protect Nesting Birds.
Four California Condor nests have also been
found located next to active nests of bumblebees (Bombus spp.) and honeybees
(Apis melifera - Snyder et al. 1986).
It is unknown whether or not these bees protected the condor nests from
predators, but such protection has been reported for many other bird
species that nest with bees (Haemig 2001).
Condors will feed
upon any size of dead mammal that they find. For example,
California Condors eat small mammals such as
kangaroo rats, ground squirrels, pocket gophers and rabbits; medium-sized
mammals such as Coyotes (Canis latrans),
Gray foxes (Urocyon cinereoargentineus), and Puma (Puma
concolor); and large mammals such as Mule Deer (Odocoileus hemionus), Wapiti, Grizzly Bears
(Ursus arctos) and whales (Koford 1953; Collins et al. 2000). Carrion of domestic
livestock is also eaten extensively by condors since it is now so abundant.
From a cave
in the Grand Canyon that was used by California Condors for nesting 9,000
to 13,000 years ago, bones have been found of the following prey species whose
remains are believed to have been fed to condor chicks at that time: bison (Bison sp.),
horse (Equus sp.),
mammoth (Mammuthus sp.), camel (Camelops sp.) and pygmy
mountain goat (Oreamnos harringtoni; Emslie 1987).
Like the Pleistocene California Condors of the Grand Canyon, Andean Condors today
feed upon the carrion of dead camelids, including the guanaco (Lama
guanicoe) (Sarno et al. 2000), vicuña (Vicugna vicugna) and their domesticated descendants the llama
(Lama glama) and alpaca (Vicugna pacos). Andean
Condors also feed on on a wide variety of other dead mammals (Houston
1994), and in some areas the carrion of exotic domestic livestock is now
the principal food (Lambertucci et al. 2009).
Exploitation of Marine Resources
not limit themselves to terrestrial food. In coastal regions they feed extensively on
marine life. Marine carrion is especially important to condors
living in arid regions, because in these areas grazing mammals are less
abundant and the sea often produces more food for condors than the land.
example, along the arid coasts of Peru and Chile,
the Andean Condor feeds
extensively on marine carrion washed ashore by the ocean waves. Food recorded
in its diet there includes the carcasses of whales and dolphins, maned sea
lions (Otaria byronia),
southern fur seals (Arctocephalus
australis, Peruvian Diving-petrels (Pelecanoides garnotii),
Humboldt Penguins (Spheniscus humboldti), green sea turtles (Chelonia
mydas), fishes and kelp (Murphy 1936; Housse 1945; Wallace and Temple 1987a).
During El Niño years, when high mortality of marine vertebrates
occurs, condors often benefit from an increased food supply if ocean
currents deposit the carrion on beaches that they patrol (Murphy
1936). If, however, the ocean currents wash the dead animals ashore
in densely populated urban areas that condors are afraid to visit, this
food will not be eaten by condors (Wallace & Temple 1988).
also feed on marine carrion.
For example, during the nineteenth century, when whales
were more common than they are today, Gambel (1846) wrote that it was "not
uncommon" to see California Condors feeding on the carcasses of whales that had
been cast up on the beaches of California. Near Monterey, Taylor
(1859b) also observed condors feeding "on the carcass of a whale on the sea shore."
Further north, along the coast of Oregon during the winter of 1805-1806,
Meriwether Lewis and William Clark observed California Condors feeding upon the
remains of a whale and on fishes that had been "thrown up by the waves on the
seacoast." During the winter months that these renowned explorers spent
near the Columbia River estuary, they found the condor "more abundant below
tidewater than above (Lewis & Clark [1804-1806] 1990)."
Even during the late twentieth century, when the California Condor
was almost extinct in the wild, fragments of marine molluscs, including the Pismo
Clam (Tivela stultorum),
Common California Venus (Chione californiensis), and Moon Shell (Polinices
were frequently found in condor nest caves in southern California (Collins et al. 2000),
suggesting some foraging by parent condors in the inter-tidal zone.
living along arid coasts also fly out to offshore islands to raid seabird colonies of eggs
and young. For example,
when Murphy (1925) visited Asia Island off the coast of central Peru, he found Andean Condors, Turkey Vultures and
gulls feeding on eggs at a large colony of the Guanay Cormorant (Phalacrocorax
bougainvilli) that contained "countless eggs and young."
According to Murphy, the condors, vultures and gulls were all "more
abundant and rapacious" there than anywhere else he had visited. One condor stood in the middle of the cormorant colony, "with
a circle of abandoned and rifled nests roundabout." When this condor
was shot and picked up by its feet, "the albumen and mostly unbroken
yolks of a round dozen of fresh eggs slid out of its gullet." Because
virtually no shell fragments were visible in this meal, Murphy suggested
that "condors must suck the contents of the eggs through their
During his visit to Asia Island, Murphy observed a minimum of 18 condors "flying
back and forth slowly" over the cormorant colony and, before noon, watched them all fly back to the mainland.
He added that at Santa Rosita, a nearby island, a reliable informant observed 36
condors descend together upon a Guanay Cormorant colony.
On San Gallan,
another island off the coast of Peru, Murphy (1925) found that Andean Condors
walked around outside the burrows of Peruvian Diving Petrels and snatched
exiting birds to eat. Thus, the Andean Condor is not just a scavenger on
these islands, but a bird of prey as well, eating adult seabirds and eggs as
well as carrion (Murphy 1925). Fortunately for the nesting seabirds, if a
condor eats their eggs and young, they can just lay new eggs to replace the lost
appears that the
California Condor also foraged on offshore islands.
For example, during the twentieth century, a resident of
Oxnard, California who was a close friend of Professor Barbara B. DeWolfe
(University of California, Santa Barbara), told DeWolfe that she often saw California Condors flying out to the
nearby Channel Islands, presumably to raid seabird nests, forage for carrion of
marine vertebrates, or eat the carrion of domestic livestock raised there
(Barbara B. DeWolfe, personal
comment to the author in the 1980s). Fossils of California Condors have also
been found on these islands, suggesting that condors exploited marine
resources there for thousands of years (Orr 1968; Guthrie 1992, 1993).
other Scavenger Birds
descend to feed on a carcass, they often meet other species of scavengers
there that are already feeding. Sometimes condors peacefully join
these other scavengers in feeding, but other times they must fight to
displace them or else wait until they have finished eating and leave. Fortunately for
condors, their larger body size helps them win encounters with other
For example, in Peru, Wallace and Temple (1987a) studied
interactions of Andean Condors with other vulture species at carcasses,
and found that the larger species dominated the smaller species.
Since condors had the largest body size, they occupied the top of the
dominance hierarchy and the other vultures yielded to them. Turkey
vultures were usually the first to arrive at a carcass, Black Vultures
second, and condors third. Yet, when the condors arrived, the other
vulture species generally yielded to them. Condors won 100% of aggressive
Turkey Vultures, 94% with Black Vultures and 100% with King Vultures (Sarcoramphus papa).
At no time did a King Vulture (the second largest species) initiate an
encounter with a condor.
In the mountains of Argentina, Condors arrived to
carcasses before other scavenging animals 76% of the time (Carrete et al.
2010). On the plains, however, Black Vultures arrived first 72% of
the time. These results can be explained by population differences, since
Andean Condors are more abundant than Black Vultures in the mountains,
but less abundant than them on the plains. Although the Black
Vulture is smaller in size, data suggests that when Black Vultures are abundant at carcasses
they sometimes prevent Andean Condors from joining (Carrete
et al. 2010).
America, the Turkey Vulture also arrives early to
carcasses, often first because of its well-developed sense of smell. However,
in some regions ravens are more abundant than Turkey Vultures and so
often arrive first at a carcass, followed by Golden Eagles and
then California Condors
(Snyder & Snyder 2000). The much larger condor dominates both the
Turkey Vulture and the Raven, causing them to yield during encounters.
However, interactions between the California Condor and the Golden Eagle
are more complex and do not simply follow the dominance hierarchy based on
size. California Condors weigh approximately twice as
much as Golden Eagles, yet usually wait for the latter to finish eating
and leave before stepping up to a carcass, perhaps fearing the eagles'
(Snyder & Snyder 2000). On some occasions, perhaps when very
hungry, adult California Condors do challenge eagles and displace them
from carcasses, however juvenile condors have not been seen to do so
(Snyder & Snyder 2000).
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Photograph at top of page: An adult
Andean Condor soars in the Quebrada del Condoritos National Park, near
Córdoba, Argentina. Photo by Yuri.