Heavy Metal Levels in Herons, Egrets, Night-Herons, and Ibises
Egrets, have been used extensively as bioindicators (Burger and Gochfeld 1993d; Goutner and Furness 1997; Boncompagni et al. 2003; Zhang et al. 2006; Kim et al. 2009; Shahbaz et al. 2013).
In this chapter, we examine levels in eggs and feathers both temporally and spatially. We first examine metal levels by species from Barnegat Bay, then present metal levels from the same species from other Northeast bays, and then compare metal levels across species. Wherever possible, we present spatial and temporal trends from both eggs and feathers. Feathers from fledglings not yet able to fly more than a few meters are the most useful because they reflect contaminants acquired locally from food gathered by their parents (Burger 1993). Some studies analyzed metals in wing
feathers (e.g., Hoffman and Curnow 1979), but primary molt pattern is sometimes unknown, and removal of a primary from fledglings is not a good idea. Metal levels in eggs represent female exposure, which usually represents local exposure as parents are near their colony sites for many weeks before egg-laying. Egg levels also indicate natal exposure from mother to chick.