Laboratorio Ecotono

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 non destructive 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g/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 Southamerican countries, including the banning of lead ammunitions to protect carnivores consuming hunted animals.

Current understanding of how animals search for and exploit food resources is based on microeconomic models. Although widely used to examine feeding, such constructs should inform other energy-harvesting situations where theoretical assumptions are met. In fact, some animals extract non-food forms of energy from the environment, such as birds that soar in updraughts. This study examined whether the gains in potential energy (altitude) followed efficiency-maximising predictions in the world’s heaviest soaring bird, the Andean condor (Vultur gryphus). Animal attached technology was used to record condor flight paths in three-dimensions. Tracks showed that time spent in patchy thermals was broadly consistent with a strategy to maximise the rate of potential energy gain. However, the rate of climb just prior to leaving a thermal increased with thermal strength and exit altitude. This suggests higher rates of energetic gain may not be advantageous where the resulting gain in altitude would lead to a reduction in the ability to search the ground for food. Consequently, soaring behaviour appeared to be modulated by the need to reconcile differing potential energy and food energy distributions. We suggest that foraging constructs may provide insight into the exploitation of non-food energy forms, and that non-food energy distributions may be more important in informing patterns of movement and residency over a range of scales than previously considered.