Recent impact of DDT contamination on Black Stork eggs

Abstract

The contamination with DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) and its breakdown products as a potential cause of population decline of Black Stork has been studied in Latvia since 2008. In order to test if contamination is local or widely distributed we collected failed eggs from nests also in Estonia, Belarus, Poland, Czech Republic, Germany and Belgium. DDT or its breakdown products were found in all analysed eggs. The ratio of p,p 0 -DDT as a proportion of all DDT products increased during the years of our research. Since the Black Stork has so far not been mentioned as a species affected by DDT we do not have information about its critical contamination effect levels. However, we also present data suggesting that DDT contamination might have affected Black Stork historically. Current data suggest that the reduction of eggshell thickness has not (yet) reached the levels described as critical for other affected species. However, we found a significant reduction of egg volumes, which in turn negatively affects hatching, as eggs below a threshold size fail to hatch. The ratio of small eggs versus normal eggs has increased by almost 10 % in recent years and is strikingly higher as compared to the pre-DDT period. There is also a significant correlation between eggs of reduced size and their respective DDE (1,1-bis(4-chlorophenyl)-2,2-dichloroethene) values.

Low juvenile survival threatens the Black Stork Ciconia nigra in northern Europe

“…This may have acted in concert with climate change, particularly increased temperatures and decreased precipitation in July and August, the hottest summer months in northern Europe, when young storks fledge. Secondly, Baltic Black Storks are affected by recent DDT contamination, which has likely increased mortality among nestlings and fledglings (Strazds et al 2015). Thirdly, Black Stork nestlings and fledglings may suffer from predation.…”

Assessing Mercury Pollution Using Black Stork Eggshells

“…It is also unknown which processes affect the separation of the membrane in non-productive (addled) eggs. Strazds et al determined the amount of DDT in eggs [19] and found that in some, eggs membranes detached very easily in some but were inseparable in others. Camera trap and webcam data show that adult birds may accidentally squash addled eggs that have remained in the nest and discard them afterwards [13].…”

“…Membranes are organic in nature, consisting mostly of elastin-like protein surrounded by muccopolysaccaride mantle. Conversely, eggshells are predominantly inorganic, and their organic compound, a polysaccharide complex with calcium binding properties, is distributed across the shell unevenly [19]. Thus, the organic matrix may be more prone to bonding mercury compounds.…”

“…Alternatively, the difference in concentrations could result from the physiology of egg formation. Bird eggs swell in utero of the female prior to the process of eggshell mineralization [19]. The location of "initial mercury" in the female body may also play some role if contaminants are deposited in the organs where organic egg content is formatted, but not the eggshells.…”

Population size and spatial distribution of the white storkCiconia ciconiain Poland in 1958 with insights into long-term trends in regional and global population

“…Surprisingly, this relationship was poorly emphasized, perhaps due to the lack of scientific evidence regarding the white stork itself. Further contamination studies clearly showed that various stork species (Van Den Bossche et al 2002;Kamiński et al 2008;Strazds et al 2015;Orłowski et al 2019) and other farmland birds (Pinowski et al 1994;Orłowski et al 2014) are susceptible to the adverse effects of agriculturally related chemicals. Therefore, it cannot be ruled out that the contamination with DDT and its breakdown products was an important cause of the past widespread population decline of white stork in Europe.…”