Organochlorine and heavy metal contamination in the eggs of the Spanish Imperial Eagle (Aquila (heliaca) adalberti) and accompanying changes in eggshell morphology and chemistry

Chemical Control of Mosquitoes and the Pesticide Treadmill: A Case for Photosensitive Insecticides as Larvicides

Insecticides reduce the spread of mosquito-borne disease. Over the past century, mosquito control has mostly relied on neurotoxic chemicals-such as pyrethroids, neonicotinoids, chlorinated hydrocarbons, carbamates and organophosphates-that target adults. However, their persistent use has selected for insecticide resistance. This has led to the application of progressively higher amounts of insecticides-known as the pesticide treadmill-and negative consequences for ecosystems. Comparatively less attention has been paid to larvae, even though larval death eliminates a mosquito's potential to transmit disease and reproduce. Larvae have been targeted by source reduction, biological control, growth regulators and neurotoxins, but hurdles remain. Here, we review methods of mosquito control and argue that photoactive molecules that target larvae-called photosensitive insecticides or PSIs-are an environmentally friendly addition to our mosquitocidal arsenal. PSIs are ingested by larvae and produce reactive oxygen species (ROS) when activated by light. ROS then damage macromolecules resulting in larval death. PSIs are degraded by light, eliminating environmental accumulation. Moreover, PSIs only harm small translucent organisms, and their broad mechanism of action that relies on oxidative damage means that resistance is less likely to evolve. Therefore, PSIs are a promising alternative for controlling mosquitoes in an environmentally sustainable manner.

Lead contamination in raptors in Europe: A systematic review and meta-analysis

Lead contamination is a widely recognised conservation problem for raptors worldwide. There are a number of studies in individual raptor species but those data have not been systematically evaluated to understand raptor-wide lead exposure and effects at a pan-European scale. To critically assess the extent of this problem, we performed a systematic review compiling all published data on lead in raptors (1983-2019) and, through a meta-analysis, determined if there was evidence for differences in exposure across feeding traits, geographical regions, between hunting and non-hunting periods, and changes over time. We also reviewed the impact of lead on raptors and the likely main source of exposure. We examined 114 studies that were unevenly distributed in terms of time of publication and the countries in which studies were performed. Peer-reviewed articles reported data for 39 raptor species but very few species were widely monitored across Europe. Obligate (vultures) and facultative scavengers (golden eagle, common buzzard and white-tailed sea eagle) accumulated the highest lead concentrations in tissues and generally were the species most at risk of lead poisoning. We found no evidence of a spatial or decadal trend in lead residues, but we demonstrated that high lead blood levels relate to hunting season. Exposure at levels associated with both subclinical and lethal effects is common and lead from rifle bullets and shot is often the likely source of exposure. Overall, our review illustrates the high incidence and ubiquity of lead contamination in raptors in Europe. However, we did not find studies that related exposure to quantitative impacts on European raptor populations nor detailed studies on the impact of mitigation measures. Such information is urgently needed and requires a more harmonised approach to quantifying lead contamination and effects in raptors across Europe.

Presence and impact of Stockholm Convention POPs in gull eggs from Spanish and Portuguese natural and national parks

The aim of the present work was to comparatively assess the occurrence and impact of persistent organic pollutants (POPs) in nine natural and national parks from Spain and Portugal using gull eggs (Larus michahellis and L. audouinii) as bioindicators of environmental contamination. Sampling was performed during the breeding season of 2016. Compounds studied include polychlorinated biphenyls (PCBs), organochlorinated pesticides (OC pesticides), perfluorooctane sulfonic acid (PFOS) and polybrominated diphenyl ethers (PBDEs), and were analyzed using mass spectrometric based techniques. The results showed a high contamination by PCBs in all colonies, with total levels ranging from 59 to 1278ng/g wet weight (ww), despite their use is not currently authorized. OC pesticides were also present in all colonies, with a high incidence of 4,4'-DDE in gull eggs at levels up to 218±50ng/g ww in L. michahellis and 760±412ng/g ww in L. audouinii from the Ebro Delta natural park. PBDEs and PFOS were also detected at levels up to 91.7±21.3ng/g ww, which can be attributed to a more recent use. Except for PBDEs, the POP levels in eggs from L. audouinii were higher than in L. michahellis, presumably associated to the fish-based diet of the former. Finally, the effect of POP levels on eggshell parameters (volume, eggshell thickness and desiccation index) were investigated for each colony and gull species in order to evaluate the egg viability and, therefore, the reproduction success.

The excessive enrichment of trace elements in migratory and breeding red-crowned cranes (Grus japonensis) in China

The excessive enrichment of trace elements, such as Pb and Cd, from food may contribute to the decline of migratory red-crowned cranes (Grus japonensis) in China. To test this prediction, we determined the concentrations of Pb and Cd, as well as further macro and trace elements (Ca, Mg, Cu, Zn) in the target species and their prey (sediment, reed root, mollusk, arthropods, and common fish species) in both the wintering (Yancheng wetland) and breeding sites (Zhalong wetland) of cranes in China. The maximum concentrations of Pb (130 mg kg^-1 dry weight (dw)) and Cd (10.60 mg kg^-1 dw) in the sediments of breeding site and the maximum concentration of Cd (4.50 mg kg^-1 dw) in the sediments of wintering site exceeded the probable effect level values (91.30 mg kg^-1 for Pb and 3.53 mg kg^-1for Cd), suggesting the potential exposure risk of the examined species. Indeed, Pb and Cd contents of essential foods, i.e., aquatic animals, sampled in two sites were above the limit of allowable concentration recommended by the Joint Food and Agriculture Organization of the United Nations/World Health Organization food standards program. Approximately 80, 31.4, and 60.3 mg kg^-1 dw of Pb were detected in the eggshells, liver, and kidney, respectively, of the target species, and the values are above the levels of concern (1.7 mg kg^-1 for eggshell and 30 mg kg^-1 for liver and kidney) in common birds. Nevertheless, the increased Pb and Cd levels in the prey and bodies of the red-crowned cranes did not induce the levels of Ca and Mg depletion. Average contents of the macronutrients, Ca (1.38 g kg^-1 dw) and Mg (1.32 g kg^-1 dw), in the liver of the examined species exceeded the background concentrations (0.2-0.4 g kg^-1 for Ca and 0.4-0.8 g kg^-1 for Mg) in the liver of birds. Consumption of Ca-rich foods, e.g., grits and exoskeleton species, may aid in compensating the possible loss caused by the increased Pb and Cd concentrations in the bodies of the cranes.

Lead in the Red-Crowned Cranes (Grus japonensis) in Zhalong Wetland, Northeastern China: A Report

The dietary uptake of Cd and Pb may contribute to the decline of migratory red-crowned cranes (Grus japonensis) on the Asian mainland. To uncover the relevance of this hypothesis, we determined the concentrations of Pb and Cd as well as further macro and trace elements (Ca, Mg, Cu, Zn, Hg and As) in the gastric contents, gastric wall, intestinal wall, liver, kidney, muscle, and feathers of two individuals found dead in Zhalong Wetland in Northeastern China. Indeed, the Pb concentrations in the liver and kidney tissues was with 31.4 and 60.3 mg kg(-1) dry weight (dw), respectively, above concentrations considered as potentially toxic level in common birds (i.e. 30 mg kg(-1)). These Pb concentration may have possibly been associated with lethal toxicosis in this endangered species suggesting Pb as major threat for G. japonensis populations. Thus, the inputs of Pb into Zhalong Wetland should be reduced to maintain and reestablish environmental conditions supporting the population development of these migratory red-crowned cranes in the Zhalong Wetland, a critical crane habitat for the long-term sustainability of this species.

Embryonic eggshell thickness erosion: A literature survey re-assessing embryo-induced eggshell thinning in birds

Although eggshell thinning has been described mainly in the context of environmental pollution, it can also be the effect of reproductive changes induced by a developing embryo. On the basis of a literature survey of 25 bird species (26 published papers) we reviewed data on embryo-induced eggshell thinning (EET) in three groups of birds: precocials, semi-precocials and altricials. The average EET at the equator of the eggs was 6.4% (median = 4.7%). Our review did not confirm a general prediction of elevated EET at the egg equator in precocial species: altricial birds exhibited the highest EET (average = 12.0%), followed by precocials (7.6%) and semi-precocials (4.2%). We make certain critical recommendations based on the results of this study. Studies aiming to assess variation in eggshell thickness should examine intrinsic factors affecting shell properties of avian eggs, like thickness, which are the result of anatomical or reproductive changes.

Trace-element interactions in Rook Corvus frugilegus eggshells along an urbanisation gradient

Concentrations of seven trace elements [arsenic (As), chromium (Cr), nickel (Ni), lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd)] in the eggshells of Rooks Corvus frugilegus, a focal bird species of Eurasian agricultural environments, are increased above background levels and exceed levels of toxicological concern. The concentrations of Cr, Ni, Pb, Cu, and Zn are greater in eggshells from urban rookeries (large cities) compared with rural areas (small towns and villages) suggesting an urbanisation gradient effect among eggs laid by females. In the present study, the investigators assessed whether the pattern of relationships among the seven trace elements in eggshells change along an urbanisation/pollution gradient. Surprisingly, we found that eggshells with the greatest contaminant burden, i.e., from urban rookeries, showed far fewer significant relationships (n = 4) than eggshells from villages (n = 10), small towns (n = 6), or rural areas (n = 8). In most cases, the relationships were positive. As was an exception: Its concentration was negatively correlated with Ni and Cd levels in eggshells from small town rookeries (where As levels were the highest), whereas eggshells from villages (with a lower As level) showed positive relationships between As and Cd. Our findings suggest that at low to intermediate levels, interactions between the trace elements in Rook eggshells are of a synergistic character and appear to operate as parallel coaccumulation. A habitat-specific excess of some elements (primarily Cr, Ni, Cu, As) suggests their more competitively selective sequestration.

Diagnosis of heavy metal contamination in agro-ecology of Gujranwala, Pakistan using cattle egret (Bubulcus ibis) as bioindicator

The present study investigated the status of heavy metals: Lead (Pb), Cadmium (Cd), Chromium (Cr), Cobolt (Co), Silver (Ag) and Nickle (Ni) residues in egg, regurgitate and sediment samples collected from two colonies of cattle egret (Bubulcus ibis) during the breeding seasons between April and August in 2004 and 2005. The mean concentration of heavy metals in eggs and regurgitates was found higher compared to the maximum residue limit (mrl) standards prescribed by Environmental Protection Agency (EPA). A further comparison was made with a similar study conducted in China. High concentrations of heavy metals have contributed to the altered breeding behaviour of the bird species studied. Based on these findings we suggested a regular monitoring of the spread of these pollutants as these have not yet reached to the sediments.

Lead shot ingestion in two raptor species from Doñana, Spain

Diurnal raptors inhabiting wetland areas where waterfowl shooting is conducted have many opportunities to ingest lead (Pb) shot pellets when feeding on their prey. Exposure to Pb shot was studied in the Spanish imperial eagle (Aquila adalberti), an endangered species with a world population of about 150 breeding pairs, and in the red kite (Milvus milvus) from Doñana (southwest Spain). Lead exposure was evaluated by the presence of Pb shot in the pellets of both species. Results obtained by this noninvasive method demonstrated Pb shot in 11.0% of Spanish imperial eagle and 5.5% of red kite pellets. When the data of both species were pooled, there was a significant relationship between Pb shot ingestion and consumption of waterfowl during the hunting season. Pb shot found in pellets exhibited signs of erosion, and their weight distribution had peaks at 70, 170, and 240 mg, which could correspond to ammunition used for duck and goose hunting.

Organochlorine and heavy metal contamination in non-viable eggs and its relation to breeding success in a Spanish population of Lesser Kestrels (Falco naumanni)

Residues of organochlorines, polychlorinated biphenyls (PCBs), and heavy metals (mercury, cadmium, lead, copper and zinc) were measured in unhatched eggs of Lesser Kestrels (Falco naumanni) collected in southern Spain in 1988-1991. Although contaminants were detected in all eggs, the amounts were generally below levels known to have negative effects on reproduction. This is consistent with the relatively high hatching rate (about 80%) in the studied population. The nestling mortality was severe, however, apparently due to starvation. It cannot be discounted that pesticides had an indirect effect on the kestrel's breeding success by reducing the populations of prey.