Blood lead concentrations in wild birds from a polluted mining region at Villa de La Paz, San Luis Potosí, Mexico

Abstract

This investigation was undertaken to determine the concentrations of lead in bird blood samples from a mining region in central Mexico and to compare concentrations among several different feeding guilds. The study took place in the Mexican state of San Luis Potosi in a region known as “Villa de la Paz.” This is one of the most intensely exploited mining regions in central Mexico and has been actively mined for over four centuries. Lead concentrations from bird blood samples taken from four polluted sites were significantly higher than those from a control, unpolluted site (F = 6.3, P < 0.0002). Similarly, mean blood lead concentrations in birds from a highly polluted site were higher than those from a site that has intermediate pollution levels (P < 0.05). In addition, samples from insectivorous birds had significantly lower lead concentrations compared to granivores, frugivores–insectivores, and omnivores (F = 4.86, P = 0.004), and a large proportion of all individuals had blood lead concentrations indicative of low, sub-lethal toxic effects. Finally, in two polluted sites, remarkably small numbers of insectivore–frugivores, and granivores were trapped, and in one polluted site a large number of insectivores was trapped (X² = 29.9, P = 0.03), and no differences in proportions of migrants and non-migrants were found among sampling sites (X² = 0.6, P = 0.96). To date, it has not been determined to what extent constant exposure to these levels of pollution can influence health at the individual level, lifespan, and, therefore, population demography of birds from this region.

Keywords:

• Mining pollution
• birds
• Central Mexico
• ecotoxicology

Acknowledgments

We would like to thank the landowners from the “Ejido” of “Villa de la Paz” for allowing us onto their land. Ma. Del Carmen Jasso-Gordoa, Ana Martínez-Iglesias, Angel Santibañes, Edgar Romero-Aguila, and Victor H. Mendoza-Rodríguez provided valuable help during the field work phase of the study. Dr. Miguel Mora also provided valuable comments on an early version of the manuscript. Finally, the Council for Science and Technology of San Luis Potosí (COPOCYT) provided funding (grant number FMSLP-2005-C01-34), and the Institute for Science and Technology of San Luis Potosí (IPICYT) and the Faculty of Medicine from the Autonomous University of San Luis Potosí provided logistical help to successfully complete the study.