Ecology of Condors
This online review is updated and revised continuously, as soon as results
of new scientific research become available. It therefore presents
state-of-the-art information on the topic it covers.
giant raptorial birds found only in the
western hemisphere. Two species are recognized: the California Condor (Gymnogyps californianus) of North America,
and the Andean Condor (Vultur gryphus) of South America.
The Andean Condor is larger in size, with a wing span of up to 3.2 meters,
compared to 2.7 meters for the California Condor (Houston 1994).
Although the condors differ enough to be
classified into two genera, they
are more closely related to each other than to other birds (Sibley and Alquist 1990)
and their ecology is similar.
photos: Figure 1,
Figure 2, Figure 3
belong to the bird family Cathartidae (also called Vulturidae). This
family is widely known as the "New World
Vultures" because all of its living members are found only in the western
The Cathartidae also include the familiar Turkey Vulture (Cathartes aura)
Black Vulture (Coragyps atratus), as well as three other species.
All are raptorial in appearance and specialized for finding and eating the
meat of dead animals. However, unlike the similar-looking Old World
Vultures, which are related to hawks and eagles, the New World Vultures
are related to storks (Sibley & Alquist 1990).
three-page report, we review the many ways that condors interact with other
organisms and the environment, and explain why condors are endangered.
Both condors feed primarily on mammalian carrion.
They usually nest on cliffs, but some exceptions occur (see below). The
clutch size is one egg, however if it is lost a replacement egg will be
laid. Because it takes condor parents more than one year to raise a
young condor, the rate of reproduction is extremely low: usually only one
young, on average, every two years.
Andean Condors forage for food as far as 200 kilometers from their nests, while
breeding California Condors forage as far as 180 kilometers
(Wallace & Temple 1987b; Meretsky & Snyder 1992)
However, where food is concentrated in a smal
condor foraging ranges are smaller. For example, on
the arid coast of Peru, where the ocean washes ashore a "remarkably
constant food supply" of dead marine mammals and seabirds, some Andean
Condors limit their foraging to "stretches of beach several kilometers
long (MP Wallace in Snyder & Snyder 2000)."
Snyder & Snyder (2000) list three habitat
requirements for condors: (1) reasonably reliable winds or thermals upon
which to soar, (2) foraging habitat that is sufficiently open to discover
and access carrion food, and (3) adequate supplies of carrion. A
study of Andean Condors in southern Chile found that condors soared most
frequently when winds were moderate (25-48 km/hr), and soared least when
winds were strong, i.e. over 64 km/hr (Sarno et al. 2000).
nineteenth century, the California Condor ranged along the west coast of
North America from southern British Columbia south to the Sierra San Pedro Martir
of northern Baja California (Snyder & Snyder 2000). At this time,
the bird was also found in Alberta, Montana, Idaho, Utah and Arizona, but
it is unknown if the individuals observed were nesting in these inland
states or simply wandering there (Snyder & Rea 1998; Snyder & Snyder 2000). No attempts were ever made by
early ornithologists to find
California Condor nests north of San Francisco or outside California, so
the exact breeding range of the species in the nineteenth century is
Oral traditions of
the Blackfoot Indians tell of occasional sightings and possible nestings of the
California Condor in Montana and Alberta during the
nineteenth century, and of this bird's visits to their bison kills on the
plains (Schaeffer 1951). Confirmation of condor occurrence in Alberta is
provided by Fannin (1897), who observed two individuals between Calgary
and the Rocky Mountains. In Idaho, the condor was reported to be "not
uncommon" near Boise before cattleman began to "poison carcasses to kill wolves (TE
Wilcox in Lyon 1918)."
spring along the Colombia River, the
California Condor was "particularly attached to the vicinity of cascades and falls, being
attracted by the great number of dead salmon," which it fed upon
(Townsend in Audubon 1831-39) . Along this same river, the condor
was also seen "near [American] Indian villages, being attracted by the
offal of the fish thrown around their habitations (Townsend in Audubon
1831-39)." In Arizona, many distinguished ornithologists
such as Elliott Coues observed California Condors between the years 1865
and 1924, and considered them to be nesting in the state (Snyder & Rea 1998).
the beginning of the nineteenth century, the Andean Condor bred along the
entire chain of the Andes, from western Venezuela to Tierra del Fuego.
Although it is still found in much of this range, it has suffered intense
persecution from humans and has been extirpated from many localities (Ridgely
& Greenfield 2001).
According to Murphy (1932), the Andean Condor
is "a mountain bird" that keeps to high-elevations in "rainy and forested
parts of South America," but which "regularly descends to sea-level in desert districts," such as along the
arid Pacific coast of Peru and northern Chile, and also along the arid
Atlantic coast of Patagonia, from the Rio Negro south to the Strait of
Magellan (Murphy 1936).
to occurring in the main ranges of the Andes, the Andean Condor is also
found in some nearby mountain ranges. For example, it
occurs in temperate and paramo zones of the Sierra Nevada de Santa Marta
on the Caribbean coast of Colombia (Norton 1975; Hilty & Brown 1986), in the Sierra de Perijá
on the border of Colombia and Venezuela (Calchi & Viloria 1991; Hilty 2003),
and in the Sierra de Córdoba of Central Argentina (Hendrickson et al.
It also enters Brazilian territory in the state of Mato Grosso,
specifically in the "Rio Jauru region west of Cáceres (Sick 1993)."
late nineteenth and twentieth centuries, poisoning and shooting of condors caused massive declines
of many condor populations, with the result that condors of both species
disappeared from many parts of their former ranges. The situation
was especially bad for the California Condor, which became extinct in the wild from 1987 to 1992.
breeding and release programs have begun to return condors to the wild in some areas
of their former ranges
(eg. California, Arizona, Baja California, Colombia, Venezuela).
However, because nesting condor pairs of both species raise, on average, only one
young every two years, and also because poisoning and shooting continue to
cause condor deaths at alarming rates, it will take many years before the number of wild
condors returns to nineteenth century levels. Until then,
populations of both condor species will remain endangered.
species of condors were more widespread in prehistoric times than in the
nineteenth century. For example, during the Pleistocene in North and South America, condors appear to
have ranged across both continents, from the Atlantic to the Pacific,
occurring in many areas where they do not occur today.
possible explanation for the flourishing of condors during this time is
that great herds of ungulates as well as other large mammals, such as sloths and elephants, roamed
the Americas then, providing condors with a rich supply of carrion to eat.
Many of these prehistoric mammals are now extinct, so the subsequent contraction of
condor ranges may in some way be related to this fact (Emslie 1987;
Steadman & Miller 1987).
other explanations are also possible. For example, killing of condors for ceremonial purposes by
indigenous human cultures
(McMillan 1968; Snyder & Snyder 2000) may have
increased since the Pleistocene, and this activity alone could have led to
extirpation of condors from significant parts of their ranges.
Alternatively, the wind conditions that enable condors to soar may have
become less favorable in some regions, causing condors to abandon those
areas (Tonny & Noriega 1998).
fossils from the Pleistocene have been found in many localities outside
the nineteenth-century ranges of both species. For example, Andean Condor remains
13,000 years old have been found in caves at Lagoa Santa, Minas Gerais,
Brazil (Alvarenga in Sick 1993), and California Condor remains
to 16,000 years old have been found in New York, Florida, Texas, New
Mexico and Arizona, as well as in California and other western states (
& Snyder 2000; Brasso & Emslie 2006).
California Condor fossils discovered in western New York state, near the
village of Byron in Genesee County, are especially interesting because
they date from a time (9000 B.C.) when flora and fauna were reoccupying
the land following the melting of Ice Age glaciers. Boreal, coniferous
vegetation, characterized by spruce (Picea sp.) and jack pine (Pinus
banksiana), dominated the area at this time, and the climate is believed to have
been cold. Fossils found in association with those of the California
Condor at this site include extinct mastodonts (Mammut americanum),
caribou (Rangifer sp.) and wapiti (Cervus elaphus).
These findings demonstrate that the California Condor was "able to live in
a colder climate and in a boreal, coniferous setting at a time when
appropriate food (large mammal carrion) was available (Steadman & Miller
1987)." Synder & Snyder (2000) point out that the presence of
California Condors fossils in such far-flung localities as New York,
Florida, the Southwest and the Pacific Northwest suggests that this
species has "very wide habitat and climatic tolerances." Their
conclusion is also supported by the wide distribution of the California
Condor in western North America at the beginning of the nineteenth
century, a range that included the Pacific coast region from British
Colombia to Baja California, and inland to the Grand Canyon and Rocky Mountain
regions (see previous section).
Nest Site Selection
Both species of condors nest
primarily on cliffs. However, detailed information on nest-site
characteristics is currently available only for the California Condor.
Condors nest from near sea-level to an altitude of 1830 meters (Snyder et
al. 1986). High elevation nest-sites differ from those at lower
elevations in that they more frequently face south, but it is unknown if
south-facing cliffs are used more frequently because they are warmer or
simply because they are more abundant (Snyder et al. 1986).
California Condor nests are made on cliffs (in potholes, crevices, cracks
or on overhung ledges), some are also made in crevices among boulder piles
on steep slopes, and in natural cavities of large trees (Snyder et al.
1986). For example, in the Sierra Nevada, condors not only nest on
cliffs, but in cavities of the Giant Sequoia
largest species of tree in the
world (Koford 1953; Snyder et al. 1986).
One nest placed in a Sequoia was 29 meters above the ground, while
another placed in a different Sequoia was 30 meters above the ground (Snyder et al.
1986). Both were
placed in cavities that had been "produced by burn-outs of limbs into the
main trunks of the trees
(Snyder et al. 1986)."
survey of 96 Giant Sequoias, Snyder et al. (1986) found that 20% of these
trees had natural cavities, all produced by similar burn-outs,
demonstrating the dependence of California Condors on wildfire for
producing nest cavities in Giant Sequoia trees. In the Santa Lucia
Mountains of the Central California Coast, a condor nest was found "in the hollow of a tall, old robles-oak, in a steep barranca, near
the summit of one of the highest peaks (Taylor 1859)."
The male of one
California Condor pair found nesting in a
cavity of a Giant
Sequoia had, the year before, nested with another female 150 kilometers
away in a pothole on a cliff, demonstrating that at least some individual
condors show variability in choosing nesting sites
(Snyder and Johnson 1985).
Condors appear to avoid nesting in areas where Golden Eagles
chrysaetos) are common
(Snyder & Snyder 2000). Of the many nesting
sites studied in the 1980's, only one was located in a territory where
Golden Eagle sightings were frequent (Snyder & Snyder 2000). Fortunately for the
condors, this territory also had numerous nesting Prairie Falcons
(Falco mexicanus), which protected the condor
nest from eagle predation by driving the eagles away
For more information, see
the next section: Protective Nesting
earlier, the Andean Condor also nests primarily on cliffs, but like the California
Condor it is adaptable and can nest elsewhere. For example, along the
arid coast of Peru where the terrain is relatively flat, some nest sites
of this species are "little more than partially shaded crannies tucked
against boulders on modest slopes (
& Snyder 2000)."
Caves are also used for
nesting, especially when located on cliffs (Lambertucci et al. 2008).
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Photograph at top of page: Adult Andean
Condor in the Colca Canyon (Cañon del Colca) near Arequipa, Peru.
Photo by Jacob Dockendorff (Canada).