Trends in organochlorine and mercury levels in Gannet eggs

Pesticide impacts on avian species with special reference to farmland birds: a review

For decades, we have observed a major biodiversity crisis impacting all taxa. Avian species have been particularly well monitored over the long term, documenting their declines. In particular, farmland birds are decreasing worldwide, but the contribution of pesticides to their decline remains controversial. Most studies addressing the effects of agrochemicals are limited to their assessment under controlled laboratory conditions, the determination of lethal dose 50 (LD₅₀) values and testing in a few species, most belonging to Galliformes. They often ignore the high interspecies variability in sensitivity, delayed sublethal effects on the physiology, behaviour and life-history traits of individuals and their consequences at the population and community levels. Most importantly, they have entirely neglected to test for the multiple exposure pathways to which individuals are subjected in the field (cocktail effects). The present review aims to provide a comprehensive overview for ecologists, evolutionary ecologists and conservationists. We aimed to compile the literature on the effects of pesticides on bird physiology, behaviour and life-history traits, collecting evidence from model and wild species and from field and lab experiments to highlight the gaps that remain to be filled. We show how subtle nonlethal exposure might be pernicious, with major consequences for bird populations and communities. We finally propose several prospective guidelines for future studies that may be considered to meet urgent needs.

Monitoring agricultural rodenticide use and secondary exposure of raptors in Scotland

Despite the documented risk of secondary poisoning to non-target species by anticoagulant rodenticides there is no statutory post-approval monitoring of their use in the UK. This paper presents results from two Scottish monitoring schemes for the period 2000-2010; recording rodenticide use on arable farms and the presence of residues in raptor carcasses. More than three quarters of arable farms used anticoagulant rodenticides; predominately the second generation compounds difenacoum and bromadiolone. There was widespread exposure to anticoagulant rodenticides in liver tissues of the raptor species tested and the residues encountered generally reflected agricultural use patterns. As found in other studies, Red Kites (Milvus milvus) appeared to be particularly vulnerable to rodenticide exposure, 70 % of those sampled (n = 114) contained residues and 10 % died as a result of rodenticide ingestion. More unexpectedly, sparrowhawks (Accipiter nisus), which prey almost exclusively on birds, had similar exposure rates to species which prey on rodents. Although, with the exception of kites, confirmed mortality from rodenticides was low, the widespread exposure recorded is concerning. Particularly when coupled with a lack of data about the sub-lethal effects of these compounds. This raises questions regarding whether statutory monitoring of use is needed; both to address whether there are deficiencies in compliance with approval conditions or whether the recommended risk management procedures are themselves adequate to protect non-target wildlife.

Long-term trends in mercury and PCB congener concentrations in gannet (Morus bassanus) eggs in Britain

Gannet (Morus bassanus) eggs from Bass Rock (North Sea) and Ailsa Craig (eastern Atlantic) were monitored for PCB congeners (1990-2004) and total mercury (1974-2004). Congener profiles for both colonies were dominated by PCBs 153, 138, 180, 118 and 170. All declined in concentration at Ailsa Craig but some (153, 170, 180) remained stable or increased slightly at Bass Rock. Egg congener concentrations at Bass Rock were typically 10-fold higher than at Ailsa Craig by 2002, and Principal Component Analysis indicated that colony differences were driven by the dominant congeners. Egg mercury concentrations were significantly lower at Bass Rock than at Ailsa Craig and temporal trends differed, there being a significant decline at Ailsa Craig but a marginal increase at Bass Rock. Our results suggest there may be differences in contamination between the eastern Atlantic and North Sea and/or there are colony differences in prey selection and associated contaminant loads.

Seabird eggs as bioindicators of chemical contamination in Chile

Seabird eggs were used as bioindicators of chemical contamination in Chile. Brown-hooded Gull (Larus maculipennis), Kelp Gull (Larus dominicanus), Trudeau's Tern (Sterna trudeaui), Neotropic Cormorant (Phalacrocorax brasilianus), and Pink-footed Shearwater (Puffinus creatopus) eggs were sampled at different breeding sites during the 1990s. Mercury and organochlorines (PCBs, DDT, HCB, HCH, and PCP) were quantified to reveal the interspecific differences, spatial and temporal trends in contamination levels. Trudeau's Tern displayed the highest levels of mercury (486 ng g(-1) wet weight). The highest sumDDT concentrations were measured in Brown-hooded Gulls (726 ng g(-1)). PCB levels were similar among the species (102-236 ng g(-1)), but the composition of the PCB mixture was different in Pink-footed Shearwaters. With the exception of the Brown-hooded Gull, all species studied presented similar and low levels of organochlorines (sumOHa). Residues of PCB and related compounds were not detected in any of the seabird eggs analyzed in Chile. Geographical variation was low, although levels of industrial chemicals were slightly higher in eggs from Concepción Bay, and agricultural chemicals in eggs from Valdivia. Also interannual variation was low, but some evidence was found of decreasing levels in gull eggs throughout the time of the study. The causes of the low levels and small variability in space and time of environmental chemicals in Chilean seabirds are discussed. We propose the use of seabirds in future monitoring of the development of chemical contamination in Chile.

Patterns of contamination by organochlorines and mercury in the eggs of two river passerines in Britain and Ireland with reference to individual PCB congeners

Unhatched eggs were collected in 1988 and 1990 from nests of the Eurasian Dipper Cinclus cinclus and the Grey Wagtail Motacilla cinerea in Wales, eastern Scotland and south-western Ireland. Mercury concentrations in Dipper eggs (geometric means 0.45-0.91 ppm (microg g(-1)) dry mass) were significantly lower in eastern Scotland than in either south-western Ireland or Wales, where the incidence of detectable residues increased markedly between 1988 (2% of eggs) and 1990 (69%). By contrast, DDE (geometric means 0.63-3.54 ppm in lipid), TDE (<0.01-1.80 ppm), DDT (<0.01-0.65 ppm), total PCBs (3.99-10.47 ppm), HEOD (0.39-0.61 ppm) and HCB (0.02-0.13 ppm) were all significantly higher in Scottish eggs than others. Around 33-46% of the total PCB burden in Dipper and Grey Wagtail eggs could be accounted for by six congeners (IUPAC numbers 118, 180, 101, 153, 138 and 170). Amongst these attributable PCBs, Dipper eggs from eastern Scotland were dominated by congener 153 (2,2',4,4',5,5'-hexachlorobiphenyl), whilst Welsh and Irish eggs were dominated by congener 118 (2,3',4,4',5-pentachlorobiphenyl). With the latter exception, all the individual congeners were found at significantly higher concentrations in Scottish eggs than others. Grey Wagtail eggs were dominated by congeners 118 and 101 (2,2,4,5,5'-pentachlorobiphenyl). In general, these congeners are common, widespread, and dominant components in the eggs of other wild birds for which data are available. Consistent with the low to medium levels of contaminants found in Dipper eggs, there was only slight evidence of any toxic effects. These included moderate shell thinning in relation to increasing DDE, and some evidence that contaminants had contributed to egg failure.