Comparative Analysis of Calcium Carbonate Content in the Eggshells of Domestic Hen and Selected Wild Bird Species from the Marathwada Region of Maharashtra, India

Eggshells in birds are primarily composed of calcium carbonate (CaCO3), which provide mechanical strength and protection to the developing embryo. In this study, CaCO3 content in the eggshells of the domestic hen (Gallus gallus domesticus) as a control species, compared with three wild bird species — Baya weaver (Ploceus philippinus), Spotted munia (Lonchura punctulata), and Red-wattled lapwing (Vanellus indicus) — collected from different districts of the Marathwada region of Maharashtra, India. Eggshells were collected from poultry farms and natural nesting sites, then cleaned, dried, powdered, and analysed using a simple acid-base back titration method involving hydrochloric acid (HCl) and sodium hydroxide (NaOH). Among the species, the Red-wattled lapwing exhibited the highest average CaCO3 content (95.18% ± 1.95), followed by the domestic hen (94.93% ± 0.92), Baya weaver (93.20% ± 2.53), and Spotted munia (91.50% ± 2.43). Two-way analysis of variance (ANOVA) revealed statistically significant differences among species (F = 28.74, P < 0.001), districts (F = 4.79, P = 0.0118), and their interaction (F = 14.64, P < 0.001). These findings provide important baseline data for avian ecological studies and suggest that nesting strategies and habitat variability play key roles in eggshell mineral content. The use of backyard-raised hens as a domesticated control enhances the ecological relevance of the comparisons and highlights the utility of simple analytical methods in avian physiology and conservation research.