Specimens (4): [Male], 40848, testis 11 × 5 mm. (July 14), 7-1/2 km. W Escárcega; [Male], 40846, juv. (rectrices and remiges ensheathed basally), 30.3 gm. (July 29), and [Male], 40847, testis 12 mm., 38.0 gm. (July 29), Pueblo Nuevo X-can; [Female], 40845, ovary 6 × 3 mm., 32.5 gm. (August 4), 4 km. WSW Puerto Juarez. _Icterus auratus_ Bonaparte: Orange Oriole.--Paynter (1955a:266) reported breeding specimens taken in April and May. Two males taken in late July had fully enlarged testes. Specimens (2): [Male], 40849, testis 10 × 6 mm., 32.5 gm. (July 28), Pueblo Nuevo X-can; [Male], 40850, testis 11 × 7 mm., 33.0 gm. (July 30), 1-1/2 km. S, 1 km. E Pueblo Nuevo X-can. _Icterus gularis_ (Wagler): Black-throated Oriole.--Breeding in this species was reported by Paynter (1955a:267) only for the month of April. Breeding was apparently nearing an end in late July at Pisté, where several juveniles were taken. Adult males had moderately enlarged testes. Specimens (8): [Male], 40858, testis 5 × 3 mm., 67.2 gm. (July 20), 6-1/2 km. W Pisté; [Male], 40853, 59.0 gm. (July 21), [Female], 40851, imm., 49.9 gm. (July 21), [Male], 40852, 56.4 gm. (July 21), [Female], 40855, imm., 49.9 gm. (July 22), [Female], 40856, ovary inactive, 50.0 gm. (July 22), [Male], 40854, testis 6 × 4 mm., 63.8 gm. (July 22), and [Male], 40857, juv. (all rectrices and remiges ensheathed basally), 30.4 gm. (July 27), all from Pisté. _Icterus cucullatus_ Nelson: Hooded Oriole.--This species has not heretofore been recorded as breeding on Isla Cozumel; testes were nearly fully enlarged but probably regressing in the only specimen taken there. It had been banded (USF&WS no. 601-87003) on the island in 1961 as an adult. According to Paynter (1955a:269) there are no breeding records for this species on the mainland later than April, March 25 being the earliest date. The species was observed nesting on Isla del Carmen and adult males taken there and 5 km. S Champotón in early July were in full breeding condition. Specimens (6): [Male], 40863, testis 11 × 7 mm., 26.3 gm. (July 8), [Female], 40864, 31.4 gm. (July 8), and [Male], 40862, testis 11 × 5 mm., 24.7 gm. (July 8), 1 km. SW Puerto Real, Isla del Carmen; [Male], 40860, 26.5 gm. (July 9), and [Male], 40861, testis 10 × 5 mm., 20.9 gm. (July 11); 5 km. S Champotón; [Male], 40859, testis 8 × 5 mm., molting--7th primaries ensheathed, 27.0 gm. (August 8), 3.5 km. N San Miguel, Isla Cozumel. _Tanagra affinis affinis_ Lesson: Lesson Euphonia.--Specimens (2): [Female], 40866, 8.8 gm. (July 22), Pisté; [Male], 40865, testis 3 × 2 mm., 10.0 gm. (August 3), 4 km. WSW (Aeropuerto) Puerto Juarez.