1. =Western grebe.= ÆCHMOPHORUS OCCIDENTALIS. Rare migrant; western species, chiefly interior regions of North America.
2. =Holboell's grebe.= COLYMBUS HOLBOELLII. Rare migrant; breeds far north; range, all of North America.
3. =Horned grebe.= COLYMBUS AURITUS. Rare migrant; range, almost the same as the last.
4. =American eared grebe.= COLYMBUS NIGRICOLLIS CALIFORNICUS. Summer resident; rare in eastern, common in western Colorado; breeds from plains to 8,000 feet; partial to alkali lakes; western species.
6. =Pied-billed grebe.= PODILYMBUS PODICEPS. Summer resident, rare; common in migration; breeds in northern part of State; sometimes winters in southern part.
7. =Loon.= GAVIA IMBER. Migrant; occasionally winter resident; not known to breed in State.
8. =Yellow-billed loon.= GAVIA ADAMSII. Migrant; rare or accidental.
9. =Black-throated loon.= GAVIA ARCTICA. Rare fall and winter visitant.
37. =Parasitic jaeger.= STERCORARIUS PARASITICUS. Fall and winter resident; rare.
40. =Kittiwake.= RISSA TRIDACTYLA. Rare or accidental in winter.
49. =Western gull.= LARUS OCCIDENTALIS. Pacific Coast bird; accidental in Colorado; only one record.
51a. =American herring gull.= LARUS ARGENTATUS SMITHSONIANUS. Rare migrant; range, the whole of North America.
53. =California gull.= LARUS CALIFORNICUS. Western species; breeds abundantly in Utah; only three records for Colorado.
54. =Ring-billed gull.= LARUS DELAWARENSIS. Not uncommon summer resident; common in migration; breeds as high as 7,500 feet; range, whole of North America.
58. =Laughing gull.= LARUS ATRICILLA. Bird of South Atlantic and Gulf States; once accidental in Colorado.
59. =Franklin's gull.= LARUS FRANKLINII. Rare migrant; range, interior of North America.
60. =Bonaparte's gull.= LARUS PHILADELPHIA. Rare migrant; not uncommon in a few localities; range, whole of North America.
62. =Sabine's gull.= XEMA SABINII. Rare winter visitant; breeds in the arctic regions.
69. =Forster's tern.= STERNA FORSTERI. Rare summer resident; common migrant; habitat, temperate North America.
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.