Pyrocephalus rubinus (Boddaert): Vermillion Flycatcher.—This species was seen only in the arid scrub 2-13 km. WSW of Sisal. Breeding seemingly had ended by early August, as evidenced by four adults that showed no gonadal activity and were in advanced stages of molt.
Specimens (5): ♀, 40638, juv., 12.1 gm. (August 7), 1½ mi. S Sisal; ♀, 40640, ovary inactive, 14.1 gm., molting—6th primaries ensheathed (August 10), ♀, 40641, ovary inactive, 13.9 gm., molting—7th primaries ensheathed (August 10), and ♂, 40642, testis 2 mm., 14.6 gm., molting—5th primaries ensheathed (August 10), 13 km. WSW Sisal; ♀, 40639, testis 1 mm., 14.0 gm., molting—7th primaries ensheathed (August 18), 2 km. SW Sisal.
Tyrannus melancholicus chloronotus Berlepsch: Tropical Kingbird.—Most specimens were molting. A male and two females from Pisté taken on July 21 and a female from Pueblo Nuevo X-can (July 29) had slightly enlarged (probably regressing) gonads. Three immatures were collected and adults were seen feeding young fledglings at Pisté. There seems to be no other breeding records from the peninsula.
Specimens (10): ♀, 40650, 42 gm., (July 10), 5 km. S Champotón; ♀, 40752, ovary inactive, 43.4 gm., molting—4th primaries ensheathed (July 14), and ♂, 40651, imm., 42.5 gm. (July 15), 6-7½/# km. W Escárcega; ♀, 40645, ovary slightly enlarged (8 × 3 mm.), 47.5 gm. (July 21), ♀, 40643, ova to 1 mm., 39.3 gm. (July 21), ♂, 40644, testis 10 × 7 mm., 43.1 gm., starting to molt—1st primaries ensheathed (July 21), and ♀, 40646, imm., (July 26), Pisté; ♀, 40648, ova to 1 mm., 37.4 gm. (July 29), Pueblo Nuevo X-can; ♂, 40647, imm., 38.4 gm. (August 14), and ♀, 40649, 44.4 gm., molting—only outer 3 pairs of rectrices present and are ensheathed basally, 6th and 7th primaries ensheathed (August 15), 4 km. NNE Felipe Carrillo Puerto.
Myiodynastes luteiventris luteiventris Sclater: Sulfur-bellied Flycatcher.—The latest breeding record given by Paynter (1955a:191) is for the last week in June. A male taken on July 31 had enlarged testes. None of the following specimens was in the process of molt.
Specimens (4): ♀, 40655, 44.5 gm. (July 10), 5 km. S Champotón; ♀, 40656, ovary slightly enlarged (8 × 4 mm.), 47.0 gm. (July 15), 7½ km. W Escárcega; ♀, 40654, testis 10 × 4 mm., 39 gm. (July 31), Pueblo Nuevo X-can.
Megarhynchus pitangua mexicanus (Lafresnaye): Boat-billed Flycatcher.—I know of no previous breeding record for this species on the peninsula. The female obtained on July 25 was observed feeding young.
Specimens (2): ♀, 40658, 57.6 gm. (July 11), 5 km. S Champotón; ♀, 40657, ovary 10 × 5 mm., 59.8 gm. (July 25), Cenote Seco, 2 km. E Chichén-Itzá.
Myiozetetes similis texensis (Giraud): Vermilion-crowned Flycatcher.—Paynter (1955a:192) reported this species breeding in mid-May. A male taken on July 17 west of Escárcega had enlarged (probably regressing) testes and indicates breeding later than May.
Specimens (3): ♂, 40660, testis 6 × 3 mm., 32.0 gm. (July 17), and sex? 40661, 33.8 gm., molting—5th primaries ensheathed (July 17), 1 km. N, 13 km. W Escárcega; ♂, 40659, imm., testis 2 × 1 mm., 27.6 gm. (July 29), Pueblo Nuevo X-can.