The avian esophagus shows structural and functional differences related to feeding habits and habitat, with mucous secretions and amino acids playing key roles in protection and metabolism. The present study aimed to comparatively investigate the histological, histochemical, and amino acid profile characteristics of the cervical esophagus in the Iraqi pin-tailed sandgrouse (Pterocles alchata) and the red-wattled lapwing (Vanellus indicus). A total of eight adult individuals from each bird species (sandgrouse and lapwing) were collected from the Al-Samawah Desert, Al-Muthanna Province, and AlYusufiyah District, Baghdad Governorate, Iraq, respectively, between October 2025 and January 2026. Histological examination was performed using hematoxylin and eosin (H&E), Masson’s trichrome, periodic acid–Schiff (PAS), and Alcian blue (AB, pH 2.5) stains. Amino acid profiles of cervical esophageal tissues were analyzed using highperformance liquid chromatography (HPLC). The histological results demonstrated that the cervical esophagus in both bird species consisted of three main layers: tunica mucosa, tunica muscularis, and tunica adventitia, while the tunica submucosa and muscularis mucosae were absent. The mucosa was lined by non-keratinized stratified squamous epithelium supported by a collagen-rich lamina propria. In the Iraqi pin-tailed sandgrouse, the esophageal glands were located mainly within the lamina propria, whereas in the red-wattled lapwing, they appeared as intraepithelial glands. Histochemical staining revealed strong PAS reactivity and moderate AB reactivity in the mucous secretions of both bird species, indicating the presence of neutral and acidic mucopolysaccharide. The HPLC analysis identified 18 amino acids in the cervical esophageal tissues of both species. Glutamine showed the highest concentration, whereas methionine exhibited the lowest concentration in both birds. Most amino acids did not differ significantly between the two species (p > 0.05). However, glutamic acid showed a significant increase in the Iraqi pin-tailed sandgrouse compared with the red-wattled lapwing (p ≤ 0.05). The present findings suggest that the cervical esophagi of both bird species may exhibit structural and biochemical adaptations associated with feeding habits and ecological conditions
