Article

Landfill Use by Andean Condors in Central Chile

Authors:
  • Unión de Ornitólogo de Chile
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Abstract

We here describe Andean Condors' (Vultur gryphus) use of the biggest landfill in Chile as a food source. We monitored the landfill between 2005 and 2022. Until 2013, there was an increase in the number of condors present in the landfill. Then the number decreased until 2016, coincident with an abundant food supply on a large spatial scale, due to high mortality of cattle that were affected by extreme drought and plentiful rabbit carcasses due to outbreaks of myxomatosis. The same temporal and numerical trends were observed in both sexes and all ages. Compared to published population parameters, in the landfill the proportion of immatures was higher and that of adult males was lower; therefore, the landfill could function as a subsidy mainly for the lower strata of the dominance hierarchy of this species. There was a strong seasonality, with a low presence of condors in the warm season and maximum numbers in the cold season, likely coinciding with seasonal movements of livestock between summer and winter range lands in the high mountains, resulting in lower food abundance for condors during the cold season. This is the first characterization of the use of a landfill by a high number of Andean Condors, use that could have implications for the species' population in central Chile. Despite the apparent positive effect as a subsidy, waste disposals can have detrimental effects due to condors' consumption of potentially dangerous compounds. This study underscores the opportunistic nature of the Andean Condor, a species that can take advantage of rubbish dumps. Long-term Andean Condor monitoring at landfills may serve as an indicator food supply over a large spatial scale, which should be considered in conservation strategies.

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The aim of this study was to assess the exposure to organochlorine compounds (OC) in 91 primary wing feathers of avian scavengers, Turkey vulture (Cathartes aura), American black vulture (Coragyps atratus) and Southern crested caracaras (Polyborus plancus) from the southern tip of South America, in the Argentinean Patagonia. We analyzed for a series of OC including hexachlorocyclohexane (HCH) isomers, endosulfan, aldrin, dieldrin, endrin, dichlorodiphenyltrichloroethane (p,p'-DDT), dichlorodiphenyldichloroethane (p,p'-DDD), dichlorodiphenyldichloroethylene (p,p'-DDE), heptachlor and heptachlor-epoxide. This is the first study on OC in feathers of three terrestrial top carnivores from South America. OC concentrations found in the studied species were much higher than those found in feathers of raptors from Europe and Asia, which likely indicate their high use in the region, specifically in agriculture, and other possible uses of OC in this area. ∑HCH had the highest median concentration, followed by ∑Drins, ∑DDT, ∑Heptachlor, and ∑Endosulfan, similar to those reported in several food samples in Argentina. On the other hand, differences in OC profiles between species and areas may be related to feeding and migratory habits, as well as the molt period. Three individuals showed ∑DDT (DDT, DDD and DDE) concentrations in feathers related to sublethal effects. However, this comparison should be used with caution due to problems with extrapolating such data across tissues and species. Copyright © 2015 Elsevier Inc. All rights reserved.
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The prime object of this book is to put into the hands of research workers, and especially of biologists, the means of applying statistical tests accurately to numerical data accumulated in their own laboratories or available in the literature.
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We observed Andean Condors (Vultur gryphus), King Vultures (Sarcoramphus papa), Black Vultures (Coragyps atratus), Turkey Vultures (Cathartes aura), and Crested Cara-caras (Polyborus plancus) interacting at 217 animal carcasses at two sites in northern Peru. At 53 carcasses for which we knew order of arrival, Turkey Vultures usually arrived first, Black Vultures second, and condors third. On the basis of our observations of 8,066 aggressive encounters between birds, we constructed dominance hierarchies by calculating the propor-tion of encounters won by an individual of one species, sex, or age during encounters with an individual of another species, sex, or age. Within each species there was a positive rela-tionship between a bird's dominance and its age. In condors, males dominated females of the same age. Interspecific dominance was correlated positively with body mass. There are convergent similarities between the organizations of guilds of Old and New World vultures.
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Cadmium, lead, mercury, selenium, iron, zinc and arsenic levels were measured in blood samples from 59 free-ranging white stork nestlings from colonies located in three different environmental conditions in Western Spain. The reference colony was situated in "Llanos de Cáceres y Sierra de Fuentes", an Area of Special Interest for Bird Protection. A second colony was located close to (4.9 km) an urban landfill and a third one was close to both an intensive agricultural area and an urban landfill (1.5 km). Blood samples were diluted and elemental analysis was performed using inductively coupled plasma mass spectrometer. In all cases, the essential metals zinc and iron were found at the highest mean concentrations followed by lead > selenium > mercury > arsenic > cadmium. Regarding toxic metals, the highest concentrations were found for lead (ranging from 23.27 to 146.4 µg/L) although in all cases the concentrations were lower than those considered to cause subclinical effects. The metals levels detected in the chick's blood were not related to the previously reported levels in the soil next to the colonies, which may indicate that landfills are the main source of metals in white stork nestlings. The present data showed that metal levels in white stork chicks may be influenced by the use of landfills as feeding areas by the parents. However, more studies on the metal content in the feed of white stork and the influence of the distance to the landfill are necessary to establish the causality of these findings.
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1. The effect of a varying risk of predation by sparrowhawks (Accipiter nisus L.) on choice of overwinter feeding site was studied for redshank (Tringa totanus L.), on a small Scottish estuary at low tide. 2. Adult and juvenile redshank segregated into two areas, a mussel bed and a salt-marsh area, respectively. Juveniles were excluded from the mussel beds by the adults, but there were no aggressive interactions on the salt-marsh. Adults occasionally fed on the salt-marsh, particularly late in the winter. 3. A redshank on the salt-marsh was 4.8 times more likely to be killed on the salt-marsh than on the mussel beds. Redshank on the salt-marsh fed closer to cover, than those on the mussel beds: sparrowhawk attack success rate declined as redshank fed further from cover. 4. A redshank on the salt-marsh had a much higher foraging rate and overall energy intake rate (1.7 times) than a redshank foraging on the mussel beds. Adults on the mussel beds minimized risk of predation, rather than maximizing intake rate at low tide. 5. Despite higher energy intake rate anywhere on the salt-marsh compared to the mussel beds, juveniles on the salt-marsh fed very close to cover, and consequently at a greater risk of predation. Foraging rates were highest very close to cover. Although juveniles were forced to feed on the salt-marsh, they maximized intake, rather than minimizing predation with respect to choice of feeding location within the salt-marsh.
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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.
Article
Lead poisoning is not a new threat for wild birds, but it is now playing an important role in shaping raptor populations. Studies have been focused mainly on Europe, North-America, and Japan, but little is known about the situation in South-America. Lead is a serious threat for wildlife, especially for long-lived species. Nevertheless, no information is available for wild Andean condor (Vultur gryphus) populations. This species, which lives throughout the Andes Mountains, is endangered mainly in the north though it is having problems throughout its distribution. We evaluated lead exposure in the Andean condor by a nondestructive method using feathers. We determined lead concentration from 152 feathers, collected in 15 communal roosts distributed throughout almost all condor’s range in Patagonia (ca. 1500 km north–south). We also looked for the origin of this lead through the analysis of lead isotope composition of feathers and ammunition. We present here the first reference data on lead concentration for a raptor population from Argentina. Lead concentrations were generally low, however, some individuals had concentrations several times above the overall mean (up to 21 lg/g). Our results suggest that lead might come from a mix of two types of ammunition sources, one used for big game and another for hare hunting. Andean condors are at the top of the food chain, thus all the other medium-to-large sized scavengers and predators from this area can be also exposed to this threat. We highlight the need to change hunting policies in Argentina, and in other South-American countries, including the banning of lead ammunitions to protect carnivores consuming hunted animals.