Dosing of adult pigeons with as little as one #9 lead pellet caused severe δ-ALAD depression, suggesting potential adverse effects in wild populations

Relationship between blood test values and blood lead (Pb) levels in Black-headed gull (Chroicocephalus ridibundus: Laridae)

Few studies have evaluated immunosuppression due to lead accumulation below the overt toxicity threshold. If low levels of lead accumulation cause immunosuppression in birds, those birds could become more susceptible to pathogens. We aimed to determine if low levels of lead accumulation lead to immunosuppression in Black-headed gulls (Chroicocephalus ridibundus). Gulls were captured in Tokyo-bay and Mikawa-bay from January to April 2019. Their blood samples were analyzed for eight items. The data were analyzed to evaluate the correlation between lead concentrations and the variables from each bay. Lead was positively correlated with the percentage of heterophils and heterophil and lymphocyte ratio and negatively with lymphocytes. Thus, low lead accumulation levels may induce changes in percentage of the heterophils and lymphocyte.

Lead in terrestrial game birds from Spain

We analysed exposure to Pb and its relationship with lead-based ammunition in seven species of terrestrial game birds-common woodpigeon (Columba palumbus), rock dove (Columba livia), stock dove (Columba oenas), European turtle-dove (Streptopelia turtur), red-legged partridge (Alectoris rufa), Barbary partridge (Alectoris barbara) and common quail (Coturnix coturnix)-from rural and urban areas in different parts of Spain (Valencia, Castilla-La Mancha, Castilla y León, Madrid, Islas Canarias and Navarra). A total of 530 liver samples were analysed, and the presence of Pb pellets was studied in the crop, gizzard and intestine; the state and appearance of these organs were also analysed. The number of specimens suspected to have ingested Pb shot was 28 (5.6%), and the geometric mean concentration of hepatic Pb was 0.054 μg g^-1 (wet weight, ww). A low percentage of samples (4.8%) were above the abnormal exposure threshold (0.65 μg g^-1 ww), and, in these specimens, renal Pb concentrations were determined. Common woodpigeons and rock doves from Madrid were found to have high concentrations of Pb in their livers, and, so, both species can be considered to be good bioindicators of Pb contamination in rural (common woodpigeons) and urban (rock doves) environments. Partridges bred for hunting may be more prone to ingesting pellets from the environment, a fact that should be taken into account in management decisions.

Environmental Lead and Wild Birds: A Review

Lead is a persistent inorganic environmental pollutant that affects humans and animals worldwide. Avian species are especially susceptible to lead exposure through consumption of lead ammunition, lead fishing tackle, and other contaminated food sources such as aquatic species ingesting lead contaminated sediments in mining areas. Even with government regulations on the use of lead ammunition in many countries, including the United States, terrestrial, aquatic, predatory, and scavenger avian species are still at risk of exposure to potentially lethal concentrations of lead. The toxicities seen in these avian species include increased oxidative stress and decreased anti-oxidant enzymes in hepatic and renal tissue. The avian immune system is also a target of lead and displays a number of altered functions suggestive of immune suppression; however, studies in wildlife and laboratory species remain too limited for definitive statements with regard to population risk. In contrast, lead clearly inhibits reproductive capabilities in adult birds, and alters growth and development of hatchlings. Environmental remediation for lead removal, which would lower toxic exposure in wildlife, presently is a monumental and prohibitively expensive effort. Wildlife exposure will therefore continue in contaminated areas, necessitating development of new remediation practices. These plans should aim toward limiting more widespread or heavier contamination of wildlife habitats. This chapter reviews presently available information of lead toxicity in wild bird species, and suggests continued monitoring and reduction strategies to reduce lead exposure for at-risk avian populations.

Ingestion of a Single 2.3 mm Lead Pellet by Laying Roller Pigeon Hens Reduces Egg Size and Adversely Affects F1 Generation Hatchlings

Many aquatic and terrestrial avian species inadvertently ingest lead (Pb) in the form of spent or fragmented ammunition, mistaking it for food or grit. Previous studies in our laboratory have shown that ingestion of even a single 45-mg pellet can significantly increase blood-Pb levels and significantly inhibit the enzyme delta aminolevulinic-acid dehydratase (δ-ALAD) for a period of greater than 4 weeks. In the current study, proven breeder pairs of domestic Roller pigeons were housed in individual cages. The hens were orally gavaged with dH₂O vehicle, a single #9 Pb pellet (2.0 mm/45 mg) or a single #7.5 Pb pellet (2.3 mm/95 mg), placed back with the cock bird and allowed to mate for two consecutive clutches. The eggs were monitored for fertilization, shell damage, egg weight, and length during the 16- to 18-day incubation period. Hatchlings remained with the hen and cock through the weaning period (28-35 days post hatch) and were monitored for weight, development, and mortality. Weanling blood was collected for blood-Pb levels, δ-ALAD activity, red blood cell counts, total protein, and packed cell volume. Following euthanasia, weanling liver, spleen, kidney, sciatic nerve, thymus, and brain were collected for histopathology. Egg weight and length were significantly decreased in the #7.5 Pb pellet treatment group for the first clutch, and hatchling weight 7 days post hatch also was significantly less in the #7.5 Pb pellet treatment group during the first clutch. Histopathologic analysis showed increased lesions in liver, kidney, spleen, and thymus of the Pb-treated weanlings, during both the first and second clutch compared with the non-Pb-treated weanlings. These data suggest that maternal consumption of a single 95-mg Pb pellet can adversely impact egg size and hatchling organ development.

Lead poisoning and its in vivo biomarkers in Mallard and Coot from two hunting activity areas in Poland

In this study, we aimed to present the status of lead (Pb) poisoning in birds from southern Poland and the evaluation of in vivo biomarkers which may be used in the diagnosis without killing animals. This included the activity of δ-aminolevulinic acid dehydratase (ALA-d), hemoglobin (Hb) concentration, hematocrit (Ht) level and concentrations of Pb in blood, feathers and excrements. The significance of this work is the use of hunted birds which allow us to compare the signals of the chosen biomarkers with the internal response. Birds collected in the area of lower hunting activity (the Milicz ponds) revealed statistically lower Pb concentrations than birds from the Zator area. Pb poisoning was diagnosed in almost 8% of birds (including specimens from both areas), but lead pellets were found in 3%. The highest tissue concentration found was noted in kidneys of Mallard from the Zator area (36.55 μg g(-1) d.w.). Significantly higher concentrations were noted in a few samples of gizzard content (up to 1047 μg g(-1) d.w.) and excrements (up to 82.95 μg g(-1) d.w.). Hb concentration, Ht level, concentrations in feathers and excrements seem not to be efficient biomarkers at noted Pb concentrations in internal tissues (brain, pectoral muscle, kidney, liver, spleen, bone). In contrast, we found a significant negative correlation between Pb concentration in blood and ALA-d activity which confirmed that this parameter can be used successfully as in vivo biomarker of lead poisoning also in low environmental pollution.

Delta-aminolevulinic acid dehydratase (δALAD) activity in four free-living bird species exposed to different levels of lead under natural conditions

The purposes of this study were: (1) to determine the δALAD activity and δALAD ratio in blood of four free-living bird species (Griffon vulture, Eagle owl, Slender-billed gull and Audouin's gull); (2) and to investigate the correlations between δALAD activity/ratio and Pb concentrations in blood samples. A decrease was observed in δALAD activity in Griffon vultures and Eagle owls exposed to Pb. In addition, negative relationships were found between δALAD ratio or δALAD activity and Log blood Pb levels in Griffon vultures and Eagle owls, and these relationships were stronger in areas with the highest Pb exposure. We provide equations that may be helpful to estimate δALAD activity and δALAD ratio using blood Pb concentrations. Regarding gull species, δALAD activity found in the present study may be considered the normal activity in Slender-billed gull and Audouin's gull species, since very low blood Pb concentrations and no correlations were found in these species. Although both δALAD activity and δALAD ratio are sensitive biomarkers of Pb exposure and effect in birds, the use of δALAD ratio may improve the results. Besides, this study provides blood threshold concentrations at which Pb bears effects on δALAD enzyme (5µg/dl in Eagle owl; 8µg/dl in Griffon vulture; and probably >2µg/dl in Slender-billed gull and Audouin's gull). Our findings show that Eagle owl seems to be more sensitive to δALAD enzymatic inhibition by Pb than Griffon vultures. Eagle owls and Griffon vultures exhibited up to 79% and 94% decrease in δALAD activity when blood Pb concentrations exceeded 19 and 30µg/dl, respectively. Regarding the effects related with δALAD inhibition, significant negative correlations were found between δALAD activity and hematocrit in Eagle owls and Griffon vultures, which may be related to compensatory response associated with a decrease in δALAD activity. In addition, an effect on creatine kinase activity and total proteins in plasma was found in Griffon vultures. The significant negative correlations found between δALAD activity and tGSH in Griffon vulture, and between δALAD activity and Log CAT activity in Eagle owls, may be related to a protective response of antioxidant system against reactive oxygen species (ROS). The negative relationship found between δALAD activity and TBARS levels in Griffon vulture is probably related to an induction of lipid peroxidation by ROS that may be generated by δALA accumulation when δALAD activity is depressed. δALAD activity and δALAD ratio in blood are suggested as important nondestructive biomarkers for Pb exposure and effect for future biomonitoring studies in Griffon vulture and Eagle owl. Further studies are recommended to provide new data on Pb concentrations at which δALAD activity is affected in different wild bird species and to elucidate why different species tolerate Pb in different ways.