_Tiaris olivacea intermedia_ (Ridgway): Yellow-faced Grassquit.--Although females taken on Isla Cozumel exhibited no reproductive activity, two males had moderately enlarged testes. These seem to be the first records of breeding in this subspecies, which is endemic to Isla Cozumel. Specimens (5): [Male], 40908, testis 6 z 4 mm., 10.5 gm. (August 8), [Female], 40912, ovary inactive, 9.5 gm. (August 8), [Female], 40909, ovary inactive, 10.4 gm. (August 9), [Male], 40910, testis 5 × 3 mm., 11.5 gm., molting--1st primaries ensheathed (August 9), and [Male], 40911, 11.5 gm. (August 10), all from {2-1/2}-{3-1/2} km. N San Miguel, Isla Cozumel. _Sporophila torquiola morelleti_ (Bonaparte): White-collared Seedeater. --Breeding is known for this species in May and a male collected on September 2 was in breeding condition (Paynter, 1955a:293). Our records seem to be the first for the summer. Specimens taken in July and August were breeding. Specimens (7): [Female], 40918, 9.2 gm. (July 8), 1 km. SW Puerto Real, Isla del Carmen; [Male], 40919, testis 7 × 6 mm., 8.2 gm. (July 15), 7-1/2 km. W Escárcega; [Female], 40913, ovary inactive, 7.9 gm. (August 4), 4 km. WSW Puerto Juarez; [Male], 40914, testis minute, 7.8 gm. (August 14), [Female], 40915, ova to 6 mm. (August 15), [Female], 40917, ovary moderately active, 7.0 gm. (August 16), and [Male], 40916, testis 7 × 5 mm., 7.6 gm. (August 16), 4 km. NNE Felipe Carrillo Puerto. _Volatinia jacarina splendens_ (Vieillot): Blue-black Grassquit.--The only previous record of breeding is a male having slightly enlarged testes taken on June 1 (Paynter, 1955a:293). Our specimens showed various stages of reproductive activity when taken on July 10. Specimens (6): [Male], 40926, 8.9 gm. (July 10), and [Male], 40925, testis 2 × 1 mm., 8.5 gm. (July 10), 1 km. S Puerto Real, Isla del Carmen; [Male], 40924, testis 4 × 2 mm. (July 10), [Male], 40922, testis 6 × 4 mm., 8.3 gm. (July 10), [Female], 40923, ova to 2 mm., 10.3 gm. (July 10), and [Male], 40921, 8.2 gm. (July 10), 5 km. S Champotón. _Arremonops rufivirgata verticalis_ Ridgway: Olive Sparrow.--Apparently the only previous record of breeding was the laying female on June 14 reported by Paynter (1955a: 294). Males collected in July and August had enlarged testes; a juvenile, barely able to fly, was taken on August 14. Two specimens were beginning to molt.