The uptake of sodium and water across everted sacs of the jejunum and ileum of Pekin ducklings, nestling Glaucous-winged gulls, and adult Japanese quail was measured in both freshwater- and saltwater-acclimated birds to assess the importance of the avian small intestine in salt and water balance after a salt load. The jejunum and ileum together were divided into segments I-V in ducklings and gulls and segments I-IV in Japanese quail. Acclimation to sodium chloride solutions increased the uptake of sodium and water, per unit dry weight of tissue, across segments II and IV in larger ducklings, although no significant differences were observed in smaller ducklings. Sodium and water transport were significantly greater across the posterior region of the small intestine of saltwater-acclimated gulls. In Japanese quail acclimated to sodium chloride solutions, mean values for sodium and water uptake were decreased, compared with fresh-water-acclimated birds, but were not statistically significantly different. Increased uptake of water and sodium after saline acclimation appears to be correlated with the presence of functional salt glands.