Mercury in Eggs and Feathers of Great Egrets (Ardea albus) from the Florida Everglades

Abstract

Great egret (Ardea albus) eggs and nestling feathers were collected for total mercury (THg) and methylmercury (MeHg) analysis from two colonies in the Florida Everglades in 1999 and 2000. THg was present in all eggs at a mean concentration of 0.39 +/- 0.19 microg/g fresh weight (n = 33, range = 0.08-0.86 microg/g). Egg-THg levels did not differ significantly between colonies or years. MeHg concentration in eggs was 0.35 +/- 0.18 microg/g fresh weight (n = 20, range = 0.05-0.82 microg/g,), and on average represented 85% of the THg found in the egg. Concentration of THg in feathers from egret nestlings, age 11-31 days, ranged from 1.4 to 8.6 microg/g dry weight. Feather-THg levels also did not differ significantly between colonies or years. THg concentrations in feathers, normalized based on bill length, were positively correlated to THg concentrations in eggs from the same clutch. Levels of THg in both eggs and feathers were lower in 1999 and 2000 than values reported for similar samples collected in 1993-95, indicating that MeHg exposure has decreased in the southern Everglades since the mid-1990s. THg levels in eggs and nestling feathers for the period of this study were below levels associated with toxic reproductive effects. Clutch size, fledging success, and brood size observed in this study were consistent for this species in the Everglades. Collectively, these results suggest that MeHg was not adversely affecting the reproductive performance of this population during the study.

A first evaluation on the use of Ardea albus feathers as bioindicators of mercury burden in Amazonian ecosystems

“…The results presented in Table 1 agrees with previous investigations with Ardeid species, as in Florida, US where the concentration of total mercury in feathers from A. albus nestling, age 11-31 days, ranged from 1.4 to 8.6 µg.g -1 dry weight (Rumbold et al,2001), and in the vicinity of Hong Kong, China with Egretta garzetta and Nychicorax nychicorax, where the concentration of total mercury in feathers ranged from 0.0 to 7.1 µg.g -1 dry weight and 0.2 to 3.8 µg.g -1 dry weight, respectively (Connell et al, 2002).…”

Assessing the Ecological Risk of a Municipal Solid Waste Landfill to Surrounding Wildlife: a Case Study in Florida

“…Clutch sizes reported in Table 4 were likely biased low as a result of including incomplete clutches or, at the other extreme when surveyed late into incubation, clutches that may have already suffered partial predation. Yet, results of egg surveys were in the range of clutch sizes reported at other colonies (Rudegeair 1975;Kushlan 1977;Shields and Parnell 1986;Frederick 1987;Rodgers 1987b;Custer and Frederick 1990;Rumbold et al 2001;Semones 2003). This conclusion was supported by more intensive surveys in 1988 and 1989, which involved tagging White Ibis nests during egg laying, that found clutch sizes to be similar to those reported in the published literature (Rumbold 1990, data included in Table 4).…”

Patterns and Interpretation of Mercury Exposure in Freshwater Avian Communities in Northeastern North America

“…The use of piscivorous birds as bioindicators of MeHg availability and risk in freshwater systems is common (e.g., Fimreite, 1974;Barr, 1986;Scheuhammer, 1987;Rumbold et al, 2001;Henny et al, 2002;Evers et al, 2003), although insectivorous birds are increasingly being used as well (Wolfe and Norman, 1998;Gerrard and St. Louis, 2001;Adair et al, 2003). Historically, Hg exposure was primarily determined by killing birds and was therefore based on organs analysis (Thompson, 1996).…”