DDT, Chlordane, Toxaphene and PCB Residues in Newport Bay and Watershed: Assessment of Hazard to Wildlife and Human Health - Reviews of Environmental Contamination and Toxicology - page 117

Fig. 15 Relationship of DDE in eggs and eggshell thinning in brown pelicans. Figure 1 in Blus
et al. ( 1972a ) reproduced with permission from the author and from Nature
Blus et al. ( 1972b ) responded to comments by Hazeltine and by Switzer et al. in
a follow-up report. They pointed out that lipid levels in eggs decrease about
one-third from laying to hatching. Since DDE residues are localized in the lipid, the
lipid concentration of DDE will increase during incubation.
Schreiber and Risebrough ( 1972 ) published a review of the status of the brown
pelican in the United States and Baja, Mexico. They also reported on Schreiber's
work on brown pelicans in Florida. Hatching success in Florida decreased sharply
with increasing frequency of inspection by wildlife biologists. The lipid content of
Florida eggs was 5.0%. The authors claimed that very low concentrations of DDE
were associated with signifi cant thinning and that the relationship is linear from
zero concentrations of DDE. Thinning of eggshells greater than 20% usually causes
them to break during incubation. Total DDT residues in eggs collected in 1969 and
1970 in Florida were 1.2-2.9 ppm. The 9% reduction in eggshell thickness in
Florida had not yet had an observable effect on population stability. There was no
evidence that 9% shell thinning has an effect on gas exchange or water retention.
Keith and Gruchy ( 1972 ) published a comprehensive review of the past 5 years of
reports on the effects of DDE on avian wildlife. They noted a wide species variation
in eggshell thinning response to DDE residues (Fig. 16 ).
Jehl ( 1973 ) reported on the status of brown pelicans on islands off the west coast
of Baja, California. Breeding was severely impacted at most of the locations, with
empty nests and broken shells. Observations were complicated by destruction of