Eggs in private and museum collections around the world have figured prominently in studies of eggshell thinning due to contaminants such as DDT, heavy metals, and PCBs in predatory bird species such as Brown Pelicans (Pelecanus occidentalis), Bald Eagles (Halieetus leucocephalus), and Peregrine Falcons (Falco peregrinus), and were critical to these species’ recovery. In the mid-1960s, using eggs still held in private collections in England, Derek Ratcliffe determined that eggs collected prior to the first use of DDT in 1946 were thicker than eggs collected after this. (16) This finding spurred other research in the United States and around the world, and ultimately helped get the manufacturing of DDT banned in the U.S. in 1972, and in other countries after that. Eggs held at the WFVZ, in particular, contributed to settling an important court case in 2001 against the last U.S. manufacturer of DDT. However, PCBs, DDT, and other organochlorine compounds still occur in many of the waterways of the U.S., and significant thinning of eggshells and impacts on reproduction are still being observed in birds such as White-faced Ibis (Plegadis chihi). (17)
