Specimens are listed in each account according to the temporal order in which they were collected.
Bulbulcus ibis Linnaeus: Cattle Egret.—Our specimen is one of three individuals seen feeding near cattle at Rancho San Miguel on August 13 and 14.
Specimen (1): ♂, 40401, testis 6 x 2 mm., 289.5 gm. (August 14), 4 km. NNE Felipe Carrillo Puerto.
Casmerodius albus (Linnaeus): American Egret.—We took one egret from a flock of about 20 that flew low over our campsite on the morning of July 12.
Specimen (1): ♀, 40402, ovary inactive, 10 x 5 mm., 607.5 gm. (July 12), 5 km. S Champotón. Mallophaga: Ciconiphilus obscurus.
Cochlearius cochlearius (Linnaeus): Boat-billed Heron.—Three individuals were seen on a small point of land immediately south of the village on the west coast of Isla Mujeres on the afternoon of August 1. One was foraging in a small cove about one mile south of the village on the morning of August 2. Paynter (1955a) did not list the species for Isla Mujeres; our observations seem to constitute the first records for the island.
Mycteria americana Linnaeus: Wood Ibis.—A flock of about 15 flew over our camp 4 km. NNE Felipe Carrillo Puerto on August 14.
Sarcoramphus papa (Linnaeus): King Vulture.—Our specimen was one of two individuals seen at a cenote.
Specimen (1): ♂ 40403, testes inactive, 8 lbs. (July 29), 1 km. N Pueblo Nuévo X-can. Mallophaga: Colpocephalum megalops.
Carthartes burrovianus Cassin: Yellow-headed Vulture.—We saw several Yellow-headed Vultures on Isla del Carmen on July 6, 7, 8, and 9. C. burrovianus was more abundant than either Carthartes aura or Coragyps atratus in the vicinity of Champotón, where we confirmed field identifications by taking a specimen. Until Wetmore (1950) clarified the status of C. burrovianus in southern Mexico and Central America, the species had gone unnoticed or misidentified as C. aura. The Mexican Checklist (Friedmann, Griscom, and Moore, 1950) omitted C. burrovianus from the avifauna of México. Blake (1953) included Tabasco, Chiapas, and Veracruz within the range of the species, but Paynter (1955a) omitted it from his list of birds of the Yucatán Peninsula. Our specimen seemingly constitutes the first record from the peninsula.