Growth of human requirements is accelerating ecosystems transformation and also encouraging or aggravating the conservation status of wildlife. In general, rivers are used as waste disposal routes resulting from human activities (e.g. industries, cities, mining…), that drag many contaminants to the river mouths and estuaries. Biota associated with altered river ecosystems is subject to a permanent flow of contaminants, and this could affect health of trophic communities to which they belong. Thus, the main objective of the research project will be to use heavy metal levels in two bird species as an approach to determining the health of the ecosystem associated with Guadalquivir estuary (biomonitoring).On one hand, the study of Common kestrel (Falco tinnunculus) fledglings will allow us to evaluate the degree of local pollution in terrestrial trophic web. On the other hand, white stork (Ciconia ciconia) fledglings will allow us to assess heavy metal pollution in aquatic ecosystems. Additionally, stable isotopes analyses will be used in combination with heavy metals in order to assess the potential biomagnification.