Nyctidromus albicollis yucatanensis Nelson: Parauque.—This species was especially common in the vicinity of Felipe Carrillo Puerto and on Isla Cozumel, and was seen at every collecting locality. A flightless, juvenal female was obtained by local boys at Pisté on July 21. Therefore the reproduction period seems to be longer than Paynter's (1955a:141) data suggested.
Specimens (5): ♂, 40512, testis 7 × 3 mm., 75 gm. (July 10), 5 km. S Champotón; ♀, 40508, juv. (remiges and rectrices ensheathed basally), 44.2 gm. (July 21), Pisté; sex? 40510, 55.5 gm. (August 8), and ♂, 40509, testis 3 × 1 mm., 73.5 gm., molting—outermost two pairs of primaries ensheathed (August 10); 3½ km. N San Miguel, Isla Cozumel; ♂, 40511, 72.9 gm. (August 15), 4 km. NNE Felipe Carrillo Puerto.
Caprimulgus salvini badius (Bangs and Peck): Salvin's Whip-poor-will.—My only record of this species is provided by a female (40513) taken 3½ km. N San Miguel, Isla Cozumel, on August 8. The specimen weighed 58 grams, had an inactive ovary (6 × 4 mm.), and was molting (8th and 9th primaries ensheathed).
Chateura vauxi gaumeri Lawrence: Vaux Swift.—This species was seen at almost every locality visited. The only specimens obtained were brought in by a boy at Pueblo Nuevo X-can on July 30; he said he captured them in his house. Two of them were adults and four were fully-feathered young-of-the-year.
Specimens (6): ♂, 40516, testis 4 × 2 mm., ♀, 40519, ovary inactive, ♂, 40514, juv., 12.6 gm., ♂, 40515, juv., ♀, 40517, juv., and ♀, 40518, juv. (July 30) Pueblo Nuevo X-can.
Campylopterus curvipennis pampa (Lesson): Saber-wing.—A female (40522), shot 7½, km. W Escárcega on July 16, seems to provide the first record of breeding (ovum 6 mm. in oviduct) by this species on the peninsula. A non-breeding female (40521) that weighed 5.0 gms. was taken 4 km. NNE Felipe Carrillo Puerto on August 14.
Chlorostilbon canivetii canivetii (Lesson): Canivet Emerald.—This bird was seen at all localities at which we collected on the mainland.
Specimens (4): ♀, 40530, ovary moderately active, 3.0 gm. (July 22), ♂, 40525, 2.1 gm. (July 23), and sex? 40526, 2.9 gm. (July 25), Pisté; ♀, 40529, ovary inactive, 2.4 gm. (July 26), 3½ km. N Pisté.
Chlorostilbon canivetii forificatus Ridgway: Canivet Emerald.—The specimen is slightly larger than those taken on the mainland and is clearly referable to C. c. forificatus, a subspecies endemic to Isla Cozumel.
Specimen (1): ♀, 40534, ovary inactive, 2.8 gm. (August 8), 3½ km. N San Miguel, Isla Cozumel.