71. Arctic tern. Sterna paradisæa. Very rare migrant; but two records; breeding habitat, circumpolar regions.
77. Black tern. Hydrochelidon nigra surinamensis. Common summer resident; both sides of range; habitat, temperate North America; in winter south as far as Brazil and Chili.
120. Double-crested cormorant. Phalacrocorax dilophus. Perhaps breeds in Colorado, as it breeds abundantly in Utah; all present records from eastern foothills.
125. American white pelican. Pelecanus erythrorhynchos. Once a common migrant; a few remained to breed; now rare; still noted on both sides of the range.
129. American merganser. Merganser americanus. Resident; common migrant and winter sojourner; a few breed in mountains and parks; generally distributed in North America.
130. Red-breasted merganser. Merganser serrator. Rare winter sojourner; common migrant; breeds far north.
131. Hooded merganser. Lophodytes cucullatus. Rare resident both summer and winter; breeds in eastern part and in the mountains; general range, North America.
132. Mallard. Anas boschas. Very common in migration; common in winter; breeds below 9,000 feet, on plains as well as in mountains; general range, whole northern hemisphere.
134a. Mottled duck. Anas fulvigula maculosa. Rare migrant; an eastern species, sometimes wandering west to plains.
135. Gadwall. Chaulelasmus streperus. Summer resident; common in migration; breeds on plains; also in sloughs and small lakes at an elevation of 11,000 feet in southern part of State; breeds abundantly at San Luis Lakes.