Ecology of Condors

Updated: 6 September 2021

Condors are giant raptorial birds found only in the western hemisphere. There are two species: 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.

Andean Condor (Vultur gryphus). Photograph by Jean Vella (Unsplash).

Condors 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 hemisphere.

The Cathartidae also include the familiar Turkey Vulture (Cathartes aura) and 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).

In this report, we review the many ways that condors interact with other organisms and the environment, and explain why condors are endangered.

General Biology

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.

Breeding Andean Condors forage for food as far as 200 kilometers from their nests, while breeding California Condors forage as far as 180 kilometers from their nests (Wallace & Temple 1987b; Meretsky & Snyder 1992). 

However, where food is concentrated in a little area, 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). A study of California Condors found that they “were more likely to fly, soared at higher altitudes and flew over smoother terrain when weather conditions promoted either thermal or orographic updrafts, for example when turbulence and solar radiation were higher and when winds from the east and north were stronger” (Poessel et al. 2018).

Distribution

In the 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 unknown.

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).”

During 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).

At 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).

In addition 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. 2003). It also enters Brazilian territory in the state of Mato Grosso, specifically in the “Rio Jauru region west of Cáceres (Sick 1993).”

During the 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.

Fortunately, captive 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.

Prehistoric Distributions

Both 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.

One 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).

However, 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).

Condor 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 9,500 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 (Emslie 1987; Snyder & Snyder 2000; Brasso & Emslie 2006).

The 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 Condor 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.

California 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).

While most 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, California Condors not only nest on cliffs, but in cavities of the Giant Sequoia (Sequoiadendron giganteum), the 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).”

In a 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).

California Condors appear to avoid nesting in areas where Golden Eagles (Aquila 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 Associations).

As mention earlier, the Andean Condor also nests primarily on cliffs.  However, 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 (MP Wallace in Snyder & Snyder 2000).”  Caves are also used for nesting, especially when located on cliffs (Lambertucci et al. 2008).

Protective Nesting Associations

Condors 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). Not 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).

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).

Food Habits

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 a wide variety of other dead mammals (Houston 1994), and in many areas the carrion of exotic domestic livestock is now their principal food (Lambertucci et al. 2009; Duclos et al. 2020).

Exploitation of Marine Resources

Condors do 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.

For 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).

California Condors 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 sp.) 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.

Condors 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 trough-shaped tongues.”

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 ones.

It 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).

Interactions with other Scavenger Birds

When condors 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 vultures.

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 interactions with 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).

In North 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’ dangerous talons (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).

Interference between Individual Condors

Individual condors of the same species may also fight with and displace each other. In northern Patagonia, Donázar et al. (1999) studied Andean Condors at carcasses and found a dominance hierarchy based on size, sex and age. Male condors, which weighed 36-37% more than females, dominated female condors independent of age. In addition, within each sex group, older birds dominated younger birds. 

Thus, adult male condors occupied the top of the dominance hierarchy, while juvenile females occupied the bottom.

Because males and older females displaced juvenile females at carcasses, juvenile females tended to avoid foraging in the mountains where food was more abundant and encounters with males and older females more likely. Instead, they foraged more often over the plains where they were less likely to find food, but where they were more likely to avoid encounters with males and older females once they found food. Males and adult females preferred to forage in the food-rich mountains.

In northern Peru, Wallace and Temple (1987) reported slightly different results. They found that while male Andean Condors generally displaced female condors of the same age at carcasses, individual females sometimes displaced individual males that were more than one year younger.

Why Condors are Endangered

Condors are less abundant today than in the beginning of the nineteenth century because so many have been shot and poisoned by humans. Collisions with overhead electrical power lines also cause many condor deaths.

Poisoning comes mainly from three sources: (1) lead ammunition in the carrion of animals killed with firearms, (2) poisons set out to kill predators such as coyotes, wolves, pumas, bears, and (3) toxic pollutants acquired by marine organisms that condors consume.

When condors eat animals that hunters shoot with lead bullets or lead shot, they often ingest the spent lead along with the meat. Over time, the amount of lead in the condors’ bodies increases because these birds have no natural mechanisms for removing lead from their bodies. Eventually, the lead concentrations become so high that the condors die. (Pattee et al. 1990; Meretsky et al. 2000, 2001; Snyder and Snyder 2000; Church et al. 2006; Finkelstein et al. 2010).

During 1980’s, California Condors died so frequently from lead poisoning that the government captured the last remaining individuals for captive breeding, because it could see no practical way to protect the condors from this poisoning (Bessinger 2002). Starting in the 1990’s and continuing through the present, some of the captured condors and their captive-bred young were released back into the wild, with the hope that they would establish new, viable populations.

Unfortunately, because ammunition containing lead continued to be sold and used by hunters in areas where condors are released, wild condors soon began dying once again at very high rates from lead poisoning. Meretsky et al. (2001) concluded that the current death rates were so high that they approached the “disastrous mortality rates” of the 1980’s and so were unsustainable.

Fortunately, a technological solution for this problem is now available: Ammunition made of non-toxic substances, like TTB (tin, tungsten, bismuth) composites. Use of such lead-free ammunition can prevent poisoning not only of condors, but of many other animals as well, including waterfowl which often ingest lead shot while foraging in wetlands (Sanderson & Bellrose 1986). Phasing out lead in ammunition, as was done for lead in paint and gasoline, would therefore be an important step in the conservation of wildlife in general (Beissinger 2002). An added advantage is that, because of new manufacturing innovations, lead-free bullets have superior ballistics to lead bullets (Cade 2007).

Consequently, in 2008, California banned the use of lead ammunition for most hunting within the range of the condor in that state. Studies show that hunter compliance with this new law has successfully decreased lead poisoning. For example, a comparison of lead concentrations in the blood of Golden Eagles and Turkey Vultures before and after implementation of the ban on lead ammunition, found that blood lead concentrations declined dramatically within a year of the ban’s implementation (Kelly et al. 2011).

Sadly, however, lead ammunition continues to be used by hunters in other states within the range of the California Condor, so lead poisoning continues to be the major cause of death among adult condors (Gree et al 2008; Finkelstein et al. 2012; Viner et al. 2020).

In addition, South American researchers have found elevated levels of lead in Andean Condors from many localities, suggesting that this bird, like the California Condor, is also ingesting spent lead bullet fragments and shotgun pellets from carrion and dying from lead poisoning (Lambertucci 2011, Wiemeyer et al. 2016; Plaza & Lambertucci 2020). These researchers call for “urgent actions to reduce this poison in the wild.”

Many marine mammals and fishes that condors eat contain high levels of dangerous chemical pollutants such as DDE, a major metabolite of the chlorinated pesticide DDT (Tubbs 2016; Plaza & Lambertucci 2020).  In a recent study, for example, Kurle et al. (2016) report that 40% of breeding-age condors living on the California Coast have levels of DDE that have been shown in other bird species to be associated with eggshell thinning.  Since World War II, the seas along the coasts of the Americas have become more and more polluted, so other toxic chemicals now concentrated in marine life there may also be responsible for numerous breeding failures of California Condors and Andean Condors (Tubbs 2016; Meretsky & Snyder 2017; Plaza & Lambertucci 2020).

Another form of pollution: trash, also causes condor deaths.  In southern California, for example, ingestion of junk by nestling condors is a primary cause of nest failure and is preventing re-establishment of a viable breeding population (Mee et al. 2007). Of nine nestlings hatched in the wild between 2002 and 2005, four died and two ill nestlings were removed from the wild because their parents had fed them many small man-made objects made of metal, glass and plastic. Adult condors seem to have no trouble regurgitating such junk, so it is unknown why nestlings cannot do so.

Still another major source of condor mortality is shooting (Snyder & Snyder 2000). There are always a few egomaniacs who shoot down giant birds like condors to try to prove their masculinity or simply to see “what the heck that big bird is” (McMillan 1968; Snyder & Snyder 2000).

Although this and many other activities of hunters are detrimental to condors, it is wrong to conclude that hunters and condors are necessarily incompatible. In some circumstances, hunting could benefit condors.

For example, if hunters did not shoot at condors, if they used lead-free ammunition to kill game, and left part of their kills for condors to eat, they could help condors by providing more food for them (Snyder & Snyder 2000). Such “responsible” hunters might even be important to condors in areas where large predators have been extirpated, because these predators formerly left carrion for condors to eat.

Unfortunately, because every population of hunters has a few bad individuals, and it only takes a few of these to endanger a whole population of condors, hunting in condor country must be carefully monitored by competent, well-equipped police forces and all laws strictly enforced. McMillan (1968) provides disturbing accounts of what happens when irresponsible people are allowed to hunt unsupervised in condor country.

Finally, the restoration of condor populations is now threatened by an additional problem: the unnatural and naive behavior of young, captive-reared condors. These overly-tame birds have never been taught by their parents how to survive in the real world outside the zoos where they were raised, and consequently, when they are released into the wild, some approach humans without fear (Snyder & Snyder 2000; Meretsky et al. 2001; Beissinger 2002).

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Information about this Review

The author is: Dr. Paul D. Haemig (PhD in Animal Ecology)

The proper citation is:

Haemig PD 2021 Ecology of Condors. ECOLOGY.INFO 25.

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