Persistent Pollutants in Audouin's Gull (Larus audouinii) in the Western Mediterranean: A Case-study with Wide Implications?

Abstract

The possibility of persistent pollutants playing an adverse role in the reproductive success of Audouin's Gull in the western Mediterranean was examined through chemical analyses of 7 eggs of this species that did not hatch. Residues of organochlorine compounds and mercury were found.The conclusion has been reached that a further increase of present levels of DDE may well lead to a decline of the reproductive success of the species in the western Mediterranean, especially in the northern part. These observations, although limited, could have implications for further species as is already indicated by other work cited.

Trace-metals and Chlorinated Hydrocarbons in Birds' Eggs from the Delta of the Danube

“…(1973) and J.H. Koeman (as quoted by Bijleveld et al, 1979), such levels of mercury as we determined do not seem to interfere with the reproductive success of several species of shorebirds. However, Fimreite (1979) considers levels as low as 0.5 ppm to be responsible for adverse reproductive effects on Ring-neck Pheasants (Phasianus colchicus) under experimental conditions, and for the absence of young loons (Gavia spp.)…”

“…The most interesting result was the strikingly low PCB/DDE ratio in comparison with values found for aquatic birds in the Mediterranean and elsewhere. In fact, in the Danube Delta this ratio ranged from 0.3 to 0.8, in sharp contrast to the median PCB/DDE ratio of between 2 and 4 found for many seabirds of the Atlantic (Risebrough et al, 1976), between 2 and 5 for Audouin's Gull and the Herring Gull (Larus argentatus michaellis) in the Mediterranean (Bijleveld et al, 1979), between 1.1 and 7.9 in eggs of 8 species of seabirds collected in Eastern Canada from 1970 to 1976 (Pearce et al, 1979), between 1.8 and 3.8 in eggs of Cory's Shearwater in the Mediterranean (Renzoni et al, in prep. ), and between 1.1 and 3.6 in eggs of Cory's Shearwater from the eastern Atlantic (Renzoni et al, in prep.…”

Effect of environmental pollutants on wildlife — a survey

“…22 ' 23 The occurrence of chlorinated hydrocarbons in Mediterranean sea birds showed a potential effect on the reproduction of the scarce Audouin's Gull (Larus audouini) in the western Mediterranean. 24 The highest PCB levels were found in herring gull (Larus argentatus) eggs from the Rhone delta, and the highest DDE levels in herring gull eggs from Cyprus and little gull (Larus minutus) collected in winter in Malta. Toxic residue levels in birds species in North American Great Lakes were also quantified.…”

Organochlorines in Mediterranean Seabirds

“…As there have now been at least four different reports on the occurrence of chlorinated hydrocarbons in Mediterranean seabirds, so separate that none refers to any of the others, and the last of which (Bijleveld et al 1979) expresses concern about the potential effect on the reproduction of the scarce endemic Audouin's Gull (Larus audouini) in the western Mediterranean, it may be useful to compare their conclusions. The studies also included one of eggs taken from the Rhone Delta in the spring of 1972 (Mendola et al, 1977), one offish and bird migrants from the Po Delta during the following autumn (Viviani et al, 1974), and another of a small series of representative species from the whole width of the Mediterranean area in 1973-75 (Bourne & Bogan, 1976).…”