Specimen (1): ♂, 40754, juv., 16.8 gm. (August 14), 4 km. NNE Felipe Carrillo Puerto.
Thryothorus maculipectus canobrunneus (Ridgway): Spotted-breasted Wren.—According to Paynter (1955a:220) this species breeds from mid-March to May 23. Gonads were moderately active in our specimens as early as mid-July.
Specimens (4): ♀, 40758, ovary (6 × 3 mm.) granular (July 14), and ♂, 40757, testis 5 × 3 mm., 15.3 gm. (July 14), 7½ km. W Escárcega; ♀, 40755, ovary 6 × 3 mm. (ova to 1 mm.), 12.7 gm. (July 21), Pisté; ♂, 40756, ovary 4 × 3 mm., 16.8 gm. (August 3), 4 km. WSW Puerto Juarez.
Troglodytes musculus (Naumann): Southern House Wren.—Specimen (1): ♀, 40760, juv. (August 2), 4 km. WSW Puerto Juarez.
Troglodytes beani (Ridgway): Cozumel Wren.—Specimens (2): ♀, 40761, 13.3 gm. (August 9), and ♂, 40762, imm., 13.6 gm. (August 9), 3½ km. N San Miguel, Isla Cozumel.
Campylorhynchus yucatanicus (Hellmayr): Yucatán Wren.—This species was abundant in the coastal scrub west of Sisal where some breeding activity was noted. A few individuals were carrying nest material and several were feeding young. There were many old and abandoned nests and apparently the breeding season was nearly over. The only previous breeding record is for March 19 when a newly completed nest was found (Paynter, 1955a:218).
Specimens (4): ♂, 40750, imm., 32.4 gm. (August 7), 1½ mi. SW Sisal; ♀, 40751, imm., 31.2 gm. (August 18), 2 km. WSW Sisal; ♀, 40752, ovary 7 × 3 mm., 40 gm. (August 9), 4.3 km. WSW Sisal; ♀, 40753, 31.0 gm. (August 11), 6½ km. WSW Sisal.
Melanoptila glabrirostris cozumelana (Paynter): Black Catbird.—Apparently the only previous record of breeding by this species was Paynter's (1955b) mention of a male from Quintana Roo with enlarged gonads on June 26. The three adults in the collection here reported on were in nearly full reproductive activity.
Specimens (4): ♂, 40764, imm., 40.5 gm. (August 8), ♀, 40767, testis 8 × 4 mm., 42.0 gm., heavy fat (August 8), ♀, 40765, ovary active (oviduct enlarged), brood patch, 35.2 gm. (August 10), and ♂, 40766, testis 9 × 6 mm., 35 gm. (August 10), from 2½-3½ km. N San Miguel, Isla Cozumel.
Mimus gilvus (Vieillot): Tropical Mockingbird.—The only breeding record heretofore is by Paynter (1955a:226) of newly-fledged juveniles taken on May 26 and 29. Gonads in our adults were moderately active; feathers were extremely worn, but molting was not evident.