The Relationships Between Soil and Egg Parameters and Lead and Cadmium Concentrations in Eggshell and Egg Content of Collared Pratincole (Glareola pratincola).

Understanding the relationship between breeding habitats and pollutants is crucial for the reproductive success of birds. This study aimed to determine the relationships between egg characteristics and the concentrations of lead (Pb) and cadmium (Cd) in the habitat as well as in the eggshells and egg contents of the Collared Pratincole (Glareola pratincola). The study was conducted in northern Iran in the spring of 2022. Thirty nests were randomly selected and monitored until the clutch size was completed. One egg and soil samples were collected from each nest. Soil characteristics included the concentrations of Pb and Cd. Egg characteristics measured included laying order, weight, shell thickness, egg shape index, clutch size, and the concentrations of Pb and Cd in both the eggshell and egg content. The results showed that the concentrations (mg/kg) of Pb (90.47 ± 6.86) and Cd (10.29 ± 0.67) in the eggshell were significantly higher than those in the egg content (Pb: 8.72 ± 5.05; Cd: 0.64 ± 0.38) (P ≤ 0.001). A higher accumulation of these trace elements was observed in eggshells from eggs containing older embryos (Pb: P = 0.003, Cd: P = 0.022). A significant correlation was also found between Pb concentrations in the eggshell and the egg content (P = 0.016) as well as between Pb and Cd levels in the eggshell (P ≤ 0.001). This study indicates that measuring trace elements in both the eggshell and egg content can be a useful method for monitoring the potential transfer of environmental pollutants from mother to embryo. The results provide baseline information regarding the concentration of trace elements in the eggs of the Collared Pratincole and the potential for transfer from the mother to embryo, which may be used for ecotoxicology, physiology, and genetic studies to inform conservation and management plans.