Estimating the size of the Andean Condor population in the Apolobamba Mountains of Bolivia

ABSTRACT.   Population estimates of Andean Condors ( Vultur gryphus ) are urgently needed across their range to more accurately assess their conservation status and design appropriate conservation measures. From July to September 2005, six feeding stations in the Apolobamba mountain range of Bolivia were monitored for 3 days each and all visiting condors were digitally photographed and video-taped. Using distinctive marks, the size and shape of crests, and plumage patterns, we were able to individually recognize 23 adult male Andean Condors, or 30% of all observed condors. By extrapolation, we estimated a minimum population size for Apolobamba during the sampling period of 78 condors. Considering that the current estimate of the total population of Andean Condors in Colombia is 180 individuals, our results illustrate the importance of Apolobamba for Andean Condors and the potential importance of the Bolivian Andes for the conservation of this species. The methods we used to attract, observe, photograph, videotape, and recognize adult males may be useful for other populations of Andean Condors, as well as for other species of threatened vultures.     

Low‐frequency,threatened habitats drive the large‐scale distribution of Andean Condors in southern Patagonia

The analysis of factors that determine the distribution of top‐scavengers at large scales can provide clues to understanding important ecological processes and may be useful in establishing conservation and management strategies. Here, we conducted a large‐scale survey to study the distribution of the threatened Andean Condor Vultur gryphus in relation to environmental factors in southern Patagonia. This area has undergone the settlement of livestock and the introduction of exotic wildlife, although to a lesser extent than in the distribution of Condors in northern Patagonia. The aim of this study was to determine the relevance of different factors such as the availability of food resources, the availability of suitable nesting and roosting places and the presence of humans on large‐scale condor distribution. Our results show that the presence of meadows was the primary factor shaping Andean Condor distribution, despite the fact that this habitat occupies only 4% of the Patagonian landscapes. However, this habitat has a high probability of herbivore presence, so Condors seem to optimize their searching. The availability of nesting and roosting cliffs also contributed to explaining the observed distributions. Our results suggest that Condor distribution in southern Patagonia is a compromise between the spatial locations of two low‐frequency habitats – meadows and cliffs. A successful Condor conservation strategy in southern Patagonia should include the protection of these habitats and the regulation of farming expansion, including the recovery of meadows.     

Spatial and temporal patterns in the diet of the Andean condor: ecological replacement of native fauna by exotic species

The development of conservation strategies to protect viable populations of scavenging birds requires the existence of adequate and safe food supplies in the wild. Early reports on Andean condors Vultur gryphus diet recorded guanacos and rheas, the dominant herbivores since the Pleistocene, as their main food in Patagonia. However, in the past century, guanaco and rhea populations have notably decreased as a consequence of introduced livestock, and other exotic mammals have colonized the region. We study the spatial and temporal variation of the condors' diet to determine which species are being consumed by condors, and to test whether native herbivores still have a role as a food source. We analysed 371 pellets (517 prey items), collected along 500 km in northwestern Patagonia, Argentina. Our study shows that the Andean condor depends heavily (98.5%) on exotic herbivores. Their diet was made up of c . 51% sheep/goat, 24% hare/rabbit, 17% red deer and 6% cow/horse, with only 2% other mammal species. Samples from locations surveyed after 12–15 years showed a diet shift coincident with the local tendencies in the food source. The diet composition of condors using roosts within the same zone was very similar, which suggests that they may be feeding from the same area. Thus, unhealthy carcasses could impact the entire local populations. Our results show the abundance of the invasive species in northwestern Patagonia and support the idea that native mega-herbivores are ecologically extinct in this area. Exotic species management can have a decisive impact on scavenger's survival. It is necessary to apply a strategy that includes public environmental education about the problems of scavengers (e.g. use of poison, veterinary medicines and lead bullets), and a serious productive plan, including native species as a suitable source of economic development.     

Use of communal roosts by Andean Condors in northwest Patagonia, Argentina

ABSTRACT.   Andean Condors ( Vultur gryphus ) are endangered in the northern portion of their South American range, but populations are larger further south. However, throughout their range, little is known about current population sizes and dynamics. Andean Condors use cliffs with shelves as communal roosts and, from 1999 to 2001, we surveyed three of these roosts in northwestern Patagonia, Argentina, to estimate population sizes and trends. The minimum population of Andean Condors in our study area was 196, one of the highest populations recorded for this species. The maximum number of condors observed increased during our 3-yr study. However, there was a strong seasonal pattern in roost use and use also varied among roosts, possibly due to differences in their environmental characteristics, size, and room available for roosting, as well as proximity to nest sites and stage of the breeding season. In 1999 and 2000, more adults were observed than juveniles, but proportions were similar in 2001. Because we observed differential use of roosts among age classes, spatial segregation seems probable. We conclude that intensive censuses of communal roosts can provide useful information about the size, status, and dynamics of local populations. However, the large aggregations we observed may represent a potential risk for the conservation of the species because a single threat could affect multiple individuals. We suggest that a suitable conservation strategy for condors must involve the design and protection of a network of communal roosts.     

Breeding behavior of a pair of free-living Andean Condors

ABSTRACT.   The breeding behavior of Andean Condors ( Vultur gryphus ) is known primarily from observations of captive pairs. This species is the only sexually dimorphic one in its family (Cathartidae), permitting comparison of the parental care provided by each sex. We examined the breeding behavior of a pair of condors over a period of 28 mo at a nest in Patagonia, Argentina. We first observed the pair near the nest site in January 2005. Courtship displays began in April and continued until October, when incubation started. The nestling hatched in early December 2005 and fledged in June 2006. The young condor first left the nest area 10 mo after hatching and was observed at the nest site for the last time 15 mo after hatching. Both adults incubated the egg and provisioned the nestling after hatching, and at least one adult was always present at the nest site for 2 mo post hatching. During the nesting period, the male visited the nest site more often, stayed for longer periods, interacted with the chick, and brought food more frequently than the female. Additional studies of the breeding biology of wild Andean Condors are needed to improve our understanding of their population ecology and demographics and to enhance conservation efforts.     

Population status of Andean Condors in central and southern Bolivia

Andean Condors (Vultur gryphus) are a Near Threatened species that was formerly distributed along the entire length of the Andes from western Venezuela to Tierra del Fuego. Populations have been severely reduced north of Peru, but several thousand Andean Condors still exist in the southern portion of their range in Argentina and Chile. Little is known, however, about the size of the Andean Condor population in the central part of their range in Peru and Bolivia. From June to September 2012, we used feeding stations to attract Andean Condors and estimate the size and structure of the population in the eastern Andes of central and southern Bolivia. We estimated a minimum population of 253 condors, an adult male‐to‐female ratio of 1:0.6, an immature male‐to‐female ratio of 1:0.9, and an adult‐to‐immature ratio of 1:1.1. At our five survey areas, estimated abundance ranged from 15 to 100 condors per area. Males outnumbered females in three areas and the opposite was true in two areas. Our estimated adult‐to‐immature ratio, overall and in each area, suggests that the populations could be reproducing at a high rate. As previously observed in other Andean Condor populations, skewed sex ratios could be associated with differences between sexes and age classes in habitat selection. Although our results suggest that Bolivian populations of Andean Condors are still reasonably large, population monitoring is urgently needed, including use of feeding stations throughout the entire Bolivian range of the species and intensive searches for roosting and nesting sites.