Otero Pérez, X. L. Effects of nesting yellow-legged gulls (Larus cachinnans Pallas) on the heavy metal content of soils in the Cies Islands (Galicia, North-west Spain). Marine Pollution Bulletin 36, 267–272 (1998).

Cd, Cr, Cu, Pb and Zn levels were determined in faeces of the yellow-legged gull Larus cachinnans in Galicia (NW Spain), and in soils from three breeding and one reference site. The levels of Cd, Cu, Zn and Pb in the soil were significantly higher at the site with highest gull density and with the longest history of use as a breeding site (Percha) than at the reference site. Zn levels were higher than levels of the other metals in all soil and faeces samples. Mean levels of metals in faeces were 305 mg kg-1 (Zn), 60 mg kg-1 (Cu), 40 mg kg-1 (Pb), 9.8 mg kg-1 (Cr) and 5.8 mg kg-1 (Cd).