1.02 Thompson, H. M., Fernandes, A., Rose, M., White, S. & Blackburn, A. (2006)

"Predatory water birds such as herons are susceptible to bioaccumulation of pollutants through ingestion of contaminated food sources and, as they are at the top of the food chain, they are at risk of significant biomagnification (De Luca-Abbott et al., 2001)."

Qualifizierung der Quelle: A

1.03 Burton, F. G., Marquiss, M. & Tullett, S. G. (1986)

"Previous work on the effect of DDE on the breeding of the grey heron has shown that it causes eggshell thinning and egg breakage (Cooke et al., 1976; Conroy and Stephenson, 1979; Marquiss, 1983). By analysing the contents of heron eggs for DDE we have attempted to assess the effect of this insecticide on eggshell porosity and its likely consequences for successful incubation. [...]
There is an indication, however, that elevated DDE levels in the adult resulting in DDE levels above 20 ppm in the egg can increase the number of pores per egg [...] and reduce eggshell thickness [...]. Our interpretation is that the main problem posed by shell thinning due to DDE is not an excessive water loss from the egg during incubation but rather the risk of the loss of the egg due to breakage in the nest. Heron eggs are likely to break during incubation if their shells are less than 0.24 mm thick Cooke et al., 1976)."

Qualifizierung der Quelle: A

1.04 Müller, C. Y. (1983)

In einer vergleichenden Studie der DDE-Konzentrationen in Graureihereiern sowie deren Eierschalendicke konnten Unterschiede zwischen den Untersuchungen von 1945 und 1968-1973 festgestellt werden: "Thus shells collected from 1968 to 1973 tended to be thinner than those collected up to 1945 and, in the recent samples, the thinner shells were associated with higher egg residues of DDE. [...]
The proportion of pairs breaking their shells was found to be linearly related to the mean DDE content of the egg sample. [...] The broken shell sample contained a higher proportion of shells < 240 µm in thickness than the sample of egg shells being incubated [...]. This suggests that the chances of an egg surviving the incubation period intact are much reduced if the shell thickness is < 240/µm. "

Qualifizierung der Quelle: A

1.05 Voslamber, B. & Vulink, J. (2010)

Für Graureiherküken mit Knochendeformationen in einer Kolonie in England wurden mögliche Zusammenhänge mit chemischen Belastungen untersucht. Zusammenhänge mit Schwermetallbelastungen konnten nicht festgestellt werden. Die Autoren vermuten, dass die festgestellten Konzentrationen von polychlorierten Biphenylen (PCB), polychlorierten Dibenzodioxinen (PCDD) und Dibenzofuranen (PCDF) Einfluss auf die Ablagerungen von Calcium in den Knochen der Tiere und damit auf die Knochenentwicklung haben könnten.

Qualifizierung der Quelle: A

1.06 Wienburg, C. L. & Shore, R. F. (2004)

"The geometric mean liver PCB concentration in herons was 0.645 (0.522-0.797) mg/g; all but a single first-year female heron contained detectable residues. In general, adults had higher liver PCB concentrations than first-year birds [...], whilst both adult and first-year males had higher PCB residues than their female counterparts."

Qualifizierung der Quelle: A