Sf. Sundlof et al., MERCURY IN LIVERS OF WADING BIRDS (CICONIIFORMES) IN SOUTHERN FLORIDA, Archives of environmental contamination and toxicology, 27(3), 1994, pp. 299-305
Mercury was measured in livers from 144 wading birds representing seve
n species collected from four different areas in southern Flordia, inc
luding the Everglades National Park. Significant differences in hepati
c mercury concentrations were identified between birds collected from
different geographic locations, birds of different ages, dietary facto
rs, and relative amounts of body fat. Birds collected from an area enc
ompassing the central Everglades and eastern Florida Bay had significa
ntly greater concentrations of hepatic mercury than did birds from oth
er collection areas. Livers from fledgling and young adult birds conta
ined approximately three times the concentration of mercury as livers
from nestling birds. Bird species whose prey base consists of larger f
ish were found to have approximately four times the hepatic concentrat
ion of mercury as did those species which consume smaller fish or crus
taceans. Birds with minimal to moderate amounts of body fat had two to
three times the concentration of hepatic mercury as birds with relati
vely abundant body fat reserves. Four great blue herons collected from
the central Everglades contained liver mercury at concentrations typi
cally associated with overt neurologic signs (greater than or equal to
30 mu g/g). Between 30% and 80% of potential breeding-age birds colle
cted from this area contained hepatic mercury at concentrations associ
ated with reproductive impairment in ducks and pheasants. These data s
uggest that declining numbers of nesting ciconiiform birds in Florida
may be due, in part, to mercury contamination of their food supply.