Specimens (4): [Female], 40663, ova to 1 mm., 50.7 gm. (July 9), and [Male], 40664, right testis 12 mm., 65.0 gm., body feathers in early stages of molt (July 9), 5 km. S Champoton; [Male], 40665, testis 5 mm., 61.9 gm., molting--middle pair of rectrices are new, 6th primaries ensheathed (July 15), 7-1/2 km. W Escarcega; s.e.x?

40662, 59.5 gm. (August 14), 4 km. NNE Felipe Carrillo Puerto.

Mallophaga: _Philopterus_ sp.

_Myiarchus tyrannulus cooperi_ Baird: Wied Flycatcher.--This species was especially common among the coco palms on Isla del Carmen and Isla Cozumel.

Specimens (5): [Male], 40667, 36.7 gm. (July 8), [Male], 40668, 36.6 gm. (July 8), s.e.x? 40669, 39.4 gm. (July 8), and [Female], 40670, 37.3 gm. (July 8), all from 1 km. SW Puerto Real, Isla del Carmen; [Female], 40666, ovary inactive, 34.9 gm. (August 10), 3 km. N San Miguel, Isla Cozumel.

_Myiarchus tuberculifer platyrhynchus_ Ridgway: Olivaceous Flycatcher.

--Breeding specimens of this species have been known previously from April and May (Paynter, 1955a:196); records listed beyond extend the season nearly three months.

Specimens (7): [Female], 40673, ova to 5 mm. (July 10), and [Female], 40674, ovary 7 3 mm. (ova to 1 mm.) (July 11), 5 km. SW Champoton; [Female], 40745, ovary inactive, 17.5 gm., starting to molt--1st, 2nd, and 3rd primaries ensheathed (July 16), 7-1/2 km. W Escarcega; [Female], 40671, imm., 16.1 gm. (July 20) Cenote Seco, 2 km. E Chichen-Itza; [Male], 40746, 18.2 gm. (July 22), Piste; [Female], 40672, ovary inactive, 17.7 gm., molting--5th and 6th primaries and 1st secondaries ensheathed (August 15), 4 km. NNE Felipe Carrillo Puerto; [Male], 40675, left testis 13 mm., right testis 10 mm., 17.5 gm. (August 8), 3-1/2 km. N San Miguel, Isla Cozumel.

_Contopus cinereus_ (Spix): Tropical Pewee.--The regressing gonads of the male taken on July 21 in an early stage of molt suggests breeding on the peninsula.

Specimens (2): [Male], 40676 testis 6 3 mm., 11.5 gm., starting to molt--1st and 2nd primaries ensheathed (July 21), 6-1/2 km. W Piste; [Male], 40677, testis 1 mm., 12.6 mm., molting--4th, 5th, and 6th primaries and 2nd secondaries ensheathed (August 14), 4 km.

NNE Felipe Carrillo Puerto.

_Tolmomyias sulphurescens_ (Spix): Sulphury Flat-Billed Flycatcher.-- Paynter (1955a:201) presented breeding records for this species from mid-April to late June. My specimens seem to indicate that breeding extends at least into July.

Specimens (6): [Female], 40683, juv., 14.0 gm. (July 21), [Male], 40684, juv. (remiges and rectrices ensheathed basally), 14.0 gm.

(July 21), and [Male], 40682, testis 8 4 mm., 13.7 gm. (July 26), Piste and 3-1/2 km. N Piste; [Male], 40685, testis 7 4 mm., 15.3 gm., molting--1st and 2nd primaries ensheathed (July 28), and [Female], 40686, ovary inactive (July 28), Pueblo Nuevo X-can; [Male], 40687, imm., 16.0 gm. (August 15), 4 km. NNE Felipe Carrillo Puerto. Mallophaga: _Philopterus_ sp. July 28; _Myrsidea_ sp. July 28.

_Myiopagis veridicata_ (Vieillot): Yellow-crowned Elaenia.--The only previous breeding record is of a male that was taken on April 29. My only specimen has nearly fully enlarged testes.

Specimen (1): [Male], 40688, testis 7 4 mm., 13.1 gm. (July 17), 1 km. N, 13 km. W Escarcega.

_Progne subis subis_ (Linnaeus): Purple Martin.--A large migrant flock of several thousand individuals of this species was present for several days in August at Rancho San Miguel.

Specimens (3): [Female], 40723, ovary inactive, 48.6 gm. (August 14), [Female], 40724, 51.8 gm. (August 17), and [Female], 40725, imm. skull, 52.1 gm. (August 17), 4 km. NNE Felipe Carrillo Puerto.

_Petrochelidon fulva citata_ Van Tyne: Cave Swallow.--Throughout our stay at Piste, large numbers of Cave Swallows were seen flying in and out of the small opening of a well-like _cenote_ in the center of the village. Specimens were easily collected in a mist net placed across the opening. No young Cave Swallows were taken and gonads of adults were in various stages of reproductive activity. A few individuals taken were beginning to molt. Probably the swallows were nesting in the _cenote_ although the nests were inaccessible to view. Previous breeding records are for April (Paynter, 1955a:209).

Twenty-two specimens were collected, of which the following were taken at Piste, July 21-25: [Male], 40693, testis 6 3 mm., 18.4 gm.; [Male], 40696, 16.4 gm.; [Female], 40697, 18.2 gm.; [Male], 40695, 15.0 gm.; [Female], 40690, ovary inactive, 18.4 gm., molting--2nd primaries ensheathed; [Male], 40692, testis 5 3 mm., 17.9 gm.; [Female], 40698, 18.3 gm.; [Female], 40702, ovary 7 3 mm., 18.9 gm.; [Female], 40703, ovary 6 3 mm., 17.5 gm.; [Male], 40713, testis 3 mm., 18.4 gm.; [Female], 40704, 16.5 gm.; [Male], 40705, 20.3 gm.; [Male], 40699, testis 2 mm., 18.6 gm., molting--2nd primaries ensheathed; [Female], 40700, ovary 5 3 mm., 18.5 gm., molting--1st primaries ensheathed; [Female], 40701, ovary 5 3 mm., 16.5 gm., molting--1st primaries ensheathed; [Male], 40707, testis 7 5 mm., 19.9; [Male], 40708, testis 4 3 mm., 18.4 gm.; [Female], 40709, ovary 4 3 mm., 18.0 gm.; s.e.x?

40711, 18.3 gm., molting--1st and 2nd primaries ensheathed.

Additional specimens are: [Female], 40718, 16.5 gm., molting--3rd primaries ensheathed (August 16), and [Female], 40719, 18.5 gm., molting 1st primaries ensheathed (August 16), 4 km. NNE Felipe Carrillo Puerto; [Male], 40689, testis 1 mm., 16.2 gm., molting--2nd primaries ensheathed (August 10), 13 km. WSW Sisal.

Mallophaga: _Philopterus excisus_, July 21; _Myrsidea_ sp. July 21 and 25.

_Stelgidopteryx ruficollis_ Audubon: Rough-winged Swallow.--Previous records indicate that three subspecies of this species occur on the Yucatan Peninsula (Paynter, 1955a:209). One of these, _S. r. ridgwayi_, is resident. _S. r. serripennis_, representing the breeding population occurring from British Columbia and New Hampshire over much of the United States to central California, central Texas, and the Gulf states, has been taken on the peninsula in winter. Paynter referred two specimens taken in late September and three January-taken specimens to _S. r. stuarti_, the highland race that breeds from the mountains of southern Veracruz to Guatamala.

Allan R. Phillips had identified two immature individuals (40694 and 40712) from Piste as _S. r. stuarti_; one specimen from Puerto Juarez also is an immature and is nearly identical to those from Piste. Two adults from Piste (40691 and 40710) are noticeably darker dorsally than the immatures but are molting extensively and their identification to subspecies is equivocal. Two other adults (40706 and 40715) were prepared as skeletons.

Although mid-July seems early for _S. r. stuarti_ to be present on the peninsula it is not too surprising since the three specimens positively identified are immature birds and young possibly arrive earlier than do adults. But, the immature specimens possibly are atypical individuals of the resident population of _S. r. ridgwayi_.

Except for the immature individual from 5 km. WSW Puerto Juarez, all specimens were taken in mist nets over the _cenote_ at Piste where _Petrochelidon fulva_ also was obtained.

Specimens (7): [Male], 40694, imm., 16.2 gm., [Female], 40691, ovary inactive, 16.4 gm., molting--general body molt, 5th primaries and middle pair of rectrices ensheathed, [Female], 40712, imm., 14.5 gm., [Female], 40706, 14.8 gm., [Male], 40715, 16.4 gm., [Male], 40710, 18.5 gm., molting--general body molt, 1st primaries and middle pair of rectrices ensheathed, all from Piste, July 21 and 25; [Male], 40720, imm., 15.5 gm. (August 1), 5 km. WSW Puerto Juarez.

_Hirundo rustica erythrogaster_ Boddaert: Barn Swallow.--Specimen (1): [Female], 40721, imm., 7.3 gm. (August 18), apparently an early migrant, 2 km. WSW Sisal.

_Iridoprocne albilinea_ (Lawrence): Mangrove Swallow.--Specimen (1): [Female], 40722, imm. (July 7), Puerto Real, Isla del Carmen.

_Cissilopha yucatanica_ (Dubois): Yucatan Jay.--Heretofore, breeding activity has been recorded only in March (Paynter, 1955a:217). All specimens in my collection have extensively worn plumage and were beginning to molt.

Specimens (6): [Male], 40726, left testis 9 7 mm., right testis 4 2 mm., brood patch, 122.3 gm., molting--1st and 2nd primaries ensheathed (July 10), 5 km. S Champoton; [Male], 40727, testis 5 3 mm., brood patch, 125.6 gm., molting--1st and 2nd primaries ensheathed (July 11), 5 km. SW Champoton; [Female], 40728, 109.8 gm. (July 13), and s.e.x? 40729, 109.5 gm. (July 15), 7-1/2 km. W Escarcega; [Female], 40730, imm., 110.3 gm. (July 21), Piste; [Female], 40731, ovary inactive, brood patch refeathering, 121 gm., molting--2nd and 3rd primaries ensheathed (August 16), 4 km. NNE Felipe Carrillo Puerto.

_Cyanocorax yncas maya_ (van Rossem): Green Jay.--There are records of breeding by this species on the peninsula for April 28 and 29, and June 4 (Paynter, 1955a:215, 216).

Specimens (4): [Male], 40740, testis 5 3 mm., 81.2 gm. (July 16), 7-1/2 km. W Escarcega; [Female], 40739, juv., 62.3 gm. (July 21), [Male], 40737, 64.5 gm. (July 21), and [Female], 40738, 64.1 gm.

(July 21), Piste.

_Psilorhinus morio_ (Wagler): Brown Jay.--Specimens (3): [Female], 40742, 203.5 gm. (July 13), [Male], 40743, juv., 170 gm. (July 14), 7-1/2 km. W Escarcega; [Male], 40741, juv., 193.7 gm. (August 14), 4 km. NNE Felipe Carrillo Puerto.

_Thryothorus lucovicia.n.u.s albinucha_ (Cabot): Carolina Wren.--This wren formerly was considered to be a species (_T. albinucha_). In the light of evidence presented by Lowery and Berrett (1963), it is advisable to follow Paynter (1955a:219) and consider _albinucha_ to be a subspecies of _T. ludovicia.n.u.s_. The only previous evidence of breeding by this species on the peninsula was a male having slightly enlarged gonads taken by Paynter (1955a:219) on March 9.

Specimen (1): [Male], 40754, juv., 16.8 gm. (August 14), 4 km. NNE Felipe Carrillo Puerto.

_Thryothorus maculipectus can.o.brunneus_ (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): [Female], 40758, ovary (6 3 mm.) granular (July 14), and [Male], 40757, testis 5 3 mm., 15.3 gm. (July 14), 7-1/2 km. W Escarcega; [Female], 40755, ovary 6 3 mm. (ova to 1 mm.), 12.7 gm. (July 21), Piste; [Male], 40756, ovary 4 3 mm., 16.8 gm.

(August 3), 4 km. WSW Puerto Juarez.

_Troglodytes musculus_ (Naumann): Southern House Wren.--Specimen (1): [Female], 40760, juv. (August 2), 4 km. WSW Puerto Juarez.

_Troglodytes beani_ (Ridgway): Cozumel Wren.--Specimens (2): [Female], 40761, 13.3 gm. (August 9), and [Male], 40762, imm., 13.6 gm. (August 9), 3-1/2 km. N San Miguel, Isla Cozumel.

_Campylorhynchus yucatanicus_ (h.e.l.lmayr): Yucatan 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): [Male], 40750, imm., 32.4 gm. (August 7), 1-1/2 mi.

SW Sisal; [Female], 40751, imm., 31.2 gm. (August 18), 2 km. WSW Sisal; [Female], 40752, ovary 7 3 mm., 40 gm. (August 9), 4.3 km.

WSW Sisal; [Female], 40753, 31.0 gm. (August 11), 6-1/2 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): [Male], 40764, imm., 40.5 gm. (August 8), [Female], 40767, testis 8 4 mm., 42.0 gm., heavy fat (August 8), [Female], 40765, ovary active (oviduct enlarged), brood patch, 35.2 gm.

(August 10), and [Male], 40766, testis 9 6 mm., 35 gm. (August 10), from 2-1/2-3-1/2 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.

Specimens (4): [Male], 40771, testis 9 6 mm., 51.0 gm. (July 9), 5 km. S Champoton; [Female], 40770, ovary moderately active (ova to 2 mm.), brood patch, 42 gm., moderate fat (August 9), 3-1/2 km. N San Miguel, Isla Cozumel; [Female], 40768, imm., 45.2 gm., moderate fat (August 18), 2 km. WSW Sisal; [Male], 40769, testis 10 5 mm., 51.8 gm. (August 9), 13 km. WSW Sisal. Mallophaga: _Myrsidea_ sp., July 9.

_Toxostoma guttatum_ (Ridgway): Cozumel Thrasher.--Our specimen had enlarged testes and seems to represent the first record of breeding activity in the species.

Specimen (1): [Male], 40772, testis 7 4 mm., 49.5 gm. (August 10), 3-1/2 km. N San Miguel, Isla Cozumel.

_t.u.r.dus grayi_ Bonaparte: Clay-colored Robin.--Four adults were in full breeding condition.

Specimens (6): [Male], 40780, testis 13 8 mm., brood patch (July 10), 5 km. S Champoton; [Female], 40781, ova to 8 mm., 79.6 gm.