_Momotus momota lessonii_ Lesson: Blue-crowned Motmot.--For convenience, the specimens from 5 km. S Champoton are a.s.signed to _M. m. lessonii_ on the basis of measurements (wing 139 mm., tail 240 mm., culmen [from feathers] 41.0 mm.) taken on one specimen (40579), which are within the limits of the subspecies as described by Ridgway (1914). Two other specimens from that locality were prepared as skeletons and their weights are essentially the same as those Paynter (1955a) recorded for _M. m. lessonii_. According to Paynter, there is a southward clinal increase in size in this species between the smaller _M. m. exiguus_ in the northern part of the peninsula and _M. m. lessonii_ in the extreme southern part. A more extensive series of specimens from the vicinity of Champoton probably would reveal a population intermediate in size between the typical representatives of the two races.

Specimens (3): [Female], 40579, 105 gm. (July 10), [Female], 40581, 98.9 gm. (July 11), [Male], 40580, 102.5 gm. (July 11), 5 km. S Champoton.

_Pteroglossus torquatus erythrozonus_ Ridgway: Collared Aracari.--A male taken at Pueblo Nuevo X-can on July 27 and a female from 4 km. NNE Felipe Carrillo Puerto on August 15 had slightly enlarged gonads, which probably were regressing. Apparently these are the first indications of breeding activity for this species on the peninsula.

Specimens (5): [Male], 40586, testis 4 2 mm., 155 gm. (July 16), 7-1/2 km. W Escarcega; [Male], 40582, testis 10 5 mm., 169.1 gm.

(July 27), and [Female], 40583, ovary inactive, 137.3 gm. (July 29), Pueblo Nuevo X-can; [Female], 40584, ovary 10 6 mm., 169.5 gm. (August 15), and s.e.x? 40585, 148.9 gm. (August 16), 4 km. NNE Felipe Carrillo Puerto.

_Rhamphastos sulfuratus sulfuratus_ Lesson: Keel-billed Toucan.--This species was especially common west of Escarcega, where it was most often seen in small flocks of less than 10 birds. Presumably breeding had already occurred; four specimens had inactive gonads.

Specimens (7): [Female], 40589, 367.3 gm. (July 12), [Male], 40588, testis 8 3 mm., 414.5 gm. (July 14), [Female], 40590, ovary 11 mm., 347.4 gm. (July 15), [Male], 40591, testis 5 3 mm., 371 gm.

(July 15), [Male], 40593, testis 6 3 mm., 422.2 gm. (July 16) and [Male], 40592, 401.5 gm. (July 16), 6-7-1/2 km. W Escarcega; [Female], 40587, 395.5 gm. (July 28), Pueblo Nuevo X-can.

_Piculus rubiginosus yucatanensis_ (Cabot): Red-capped Green Woodp.e.c.k.e.r.--Specimen (1): [Female], 40594, ovary inactive (7 4 mm.), extensive body molt, 67.7 gm. (August 17), 4 km. NNE Felipe Carrillo Puerto. Mallophaga: _Penerirmus_ sp.

_Drycopus lineatus similis_ (Lesson): Lineated Woodp.e.c.k.e.r.--Specimen (1): [Male], 40595, molting, 141.2 gm. (July 15), 7-1/2 km. W Escarcega.

_Centurus aurifrons dubius_ (Cabot): Golden-fronted Woodp.e.c.k.e.r.--The gonads were moderately enlarged in several of the specimens taken in the first half of July. The plumage was much worn in all specimens and some were in early stages of molt. Apparently the breeding season on the peninsula extends to at least mid-July. The specimen from Isla Cozumel is a.s.signed to _C. a. dubius_, following the systematic treatment by Selander and Giller (1963).

Specimens (10): s.e.x? 40602, 75.0 gm. (July 8), and [Female], 40601, ovary 6 3 mm. (enlarged oviduct), 76.4 gm. (July 10), 1 km. S Puerto Real, Isla del Carmen; [Male], 40599, testis 6 8 mm., 101.3 gm. (July 10), and [Male], 40600, 86.0 gm. (July 11), 5 km. S Champoton; [Male], 40603, testis 5 3 mm. (July 14), and [Female], 40604, ovary 6 4 mm. (ova to 1 mm.), brood patch (July 16), 7-1/2 km. W Escarcega; s.e.x? 40596, molting, much visceral fat, 79.0 gm.

(July 22), Piste; [Female], 40597, 73.7 gm. (July 28), Pueblo Nuevo X-can; [Female], 40598, 79.6 gm. (August 15), 4 km. NNE Felipe Carrillo Puerto; [Male], 40605, testis inactive, molting, much visceral fat (August 8), 3.5 km. N San Miguel, Isla Cozumel.

_Centurus pygmaeus_ (Peters): Yucatan Woodp.e.c.k.e.r.--Paynter (1955a:166) reported evidence of breeding in this species on April 3 and May 23; a male having enlarged testes was taken on July 10.

Specimens (5): [Male], 40608, testis 6 4 mm. (July 10); [Female], 40607, 39.5 gm. (July 10), 5 km. S Champoton; [Male], 40609, testis inactive, 35.8 gm., moderate visceral fat (July 17), 1 km. N, 13 km. W Escarcega; [Female], 40606, ovary 6 4 mm. (inactive), 37.0 gm. (August 14), 4 km. NNE Felipe Carrillo Puerto; [Male], 40610, testis inactive, heavy visceral and subcutaneous fat, 41.6 gm., (August 10), 3-1/2 km. N San Miguel, Isla Cozumel.

_Phloeoceastes guatemalensis guatemalensis_ (Hartlaub): Guatemalan Ivory-billed Woodp.e.c.k.e.r.--Specimens (4): [Male], 40611, right testis 2 mm., left testis vestigial, 203.7 gm. (July 23), Piste; 40612, s.e.x? 212 gm., (July 28), and [Female], 40613, 218.1 gm. (July 30), Pueblo Nuevo X-can; [Female], 40614, 189.2 gm. (August 15), 4 km. NNE Felipe Carrillo Puerto.

_Dendrocincla anabatina_ (Sclater): Tawny-winged Woodhewer.--Specimen (1): [Male], 40615, testis 2 1 mm., 35.7 gm., molting--5th primaries and middle pair of rectrices ensheathed (July 17), 1 km. N, 13 km. W Escarcega.

_Dendrocincla h.o.m.ochroa h.o.m.ochroa_ (Sclater): Ruddy Woodhewer.--May 20 seems to be the only previous date of record for breeding in this species (Paynter, 1955a:171); our specimen extends the known season nearly three months.

Specimen (1): [Female], 40616, ovary 13 6 mm. (ova to 2 mm.), brood patch, 35.1 gm. (August 16), 4 km. NNE Felipe Carrillo Puerto.

_Sittasomus griseicapillus_ (Vieillot): Olivaceous Woodcreeper.-- Specimens (2): [Male], 40617, juv., 11.2 gm. (July 26), Piste; [Female], 40618, ovary inactive, 10.5 gm. (August 15), 4 km. NNE Felipe Carrillo Puerto.

_Xiphorhynchus flavigaster_ (Swainson): Ivory-billed Woodcreeper.-- According to Paynter (1955a:173), indications of breeding have been observed in specimens of this species taken between March 27 and June 5. A male taken on August 15 had moderately enlarged (probably regressing) testes and was well into the molt.

Specimen (1): [Male], 40619, testis 5 3 mm., 51.5 gm., molting--5th primaries and middle pair of rectrices ensheathed (August 15), 4 km. NNE Felipe Carrillo Puerto.

_Lepidocolaptes souleyetii_ (Des Murs): Streak-headed Woodhewer.--This appears to be the second specimen recorded from the peninsula (see Traylor, 1941).

Specimen (1): [Male], 40621, testis 3 1 mm., 26.6 gm., molting--6th primaries ensheathed, middle pair of rectrices are new (July 17), 1 km. N, 13 km. W Escarcega.

_Synallaxis erythrothorax_ Sclater: Rufous-breasted Spinetail.--Specimen (1): [Male], 40622, imm. skull, 16.1 gm. (August 16), 4 km. NNE Felipe Carrillo Puerto.

_Thamnophilus doliatus_ (Linnaeus): Barred Antshrike.--Specimen (1): [Female], 40623, ovary 8 5 mm. (inactive), 26 gm. (August 14), 4 km.

NNE Felipe Carrillo Puerto.

_Formicarius a.n.a.lis_ (d'Orbigny and Lafresnaye): Black-chinned Antthrush.--Specimen (1): [Male], 40624, 56.0 gm. (July 29), Pueblo Nuevo X-can.

_Pachyramphus major itzensis_ Nelson: Mexican Becard.--Previous records of breeding in this species are provided by a female obtained on July 12 (Paynter, 1955a:182) and a male taken on June 9 (Paynter, 1955b).

Specimen (1): [Male], 40625, testis 9 5 mm., 22.1 gm. (July 21), Piste.

_Platypsaris aglaiae_ (Lafresnaye): Rose-throated Becard.--All specimens have extensively worn plumage.

Specimens (3): [Male], 40628, 33.5 gm. (July 10), 5 km. S Champoton; [Female], 40626, ovary 6 3 mm., brood patch, 34.0 gm.

(July 20), [Female], 40627, ovary inactive, 33.9 gm. (July 26); 3-1/2 km. N and 6-1/2 km. W Piste.

_t.i.tyra semifasciata personata_ Jardine and Selby: Masked t.i.tyra.-- Previously, breeding information for this species has been available only for March (Paynter, 1955a:184). Adults were observed feeding young fledglings 7-1/2 km. W Escarcega on July 15, and a juvenile was taken.

Gonads of males were in full breeding condition.

Specimens (5): [Male], 40630, testis 13 6 mm., 81.3 gm. (July 14), s.e.x? 40631, juv., 55.5 gm. (July 15), [Male], 40632, testis 9 5 mm., 73 gm., molting--1st and 2nd primaries ensheathed (July 15), and [Female], 40633, 84.7 gm. (July 16), 7-1/2 km. W Escarcega; [Female], 40629, ova to 1 mm., 80.0 gm. (July 23), Piste.

_Erator inquisitor fraserii_ (Kaup): Black-capped t.i.tyra.--Breeding has been recorded by Paynter (1955a:185) on April 26. A moderately enlarged testis (probably regressing) was noted in the specimen from Piste, on July 21.

Specimens (2): [Female], 40635, 51.8 gm. (July 15), 7-1/2 km. W Escarcega; [Male], 40634, testis 6 mm., 51 gm., molting--6th primaries ensheathed (July 21), Piste.

_Pipra mentalis mentalis_ Sclater: Red-capped Manakin.--The specimens here reported seem to be the first from the peninsula in which reproductive activity has been recorded.

Specimens (2): [Male], 40637, testis 5 3 mm., 14.0 gm. (July 29), Pueblo Nuevo X-can; [Male], 40636, testis 5 2 mm., 14.6 gm.

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

_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): [Female], 40638, juv., 12.1 gm. (August 7), 1-1/2 mi. S Sisal; [Female], 40640, ovary inactive, 14.1 gm., molting--6th primaries ensheathed (August 10), [Female], 40641, ovary inactive, 13.9 gm., molting--7th primaries ensheathed (August 10), and [Male], 40642, testis 2 mm., 14.6 gm., molting--5th primaries ensheathed (August 10), 13 km. WSW Sisal; [Female], 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 Piste 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 Piste. There seems to be no other breeding records from the peninsula.

Specimens (10): [Female], 40650, 42 gm., (July 10), 5 km. S Champoton; [Female], 40752, ovary inactive, 43.4 gm., molting--4th primaries ensheathed (July 14), and [Male], 40651, imm., 42.5 gm.

(July 15), 6-7-1/2/# km. W Escarcega; [Female], 40645, ovary slightly enlarged (8 3 mm.), 47.5 gm. (July 21), [Female], 40643, ova to 1 mm., 39.3 gm. (July 21), [Male], 40644, testis 10 7 mm., 43.1 gm., starting to molt--1st primaries ensheathed (July 21), and [Female], 40646, imm., (July 26), Piste; [Female], 40648, ova to 1 mm., 37.4 gm. (July 29), Pueblo Nuevo X-can; [Male], 40647, imm., 38.4 gm. (August 14), and [Female], 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): [Female], 40655, 44.5 gm. (July 10), 5 km. S Champoton; [Female], 40656, ovary slightly enlarged (8 4 mm.), 47.0 gm. (July 15), 7-1/2 km. W Escarcega; [Female], 40654, testis 10 4 mm., 39 gm. (July 31), Pueblo Nuevo X-can.

_Megarhynchus pitangua mexica.n.u.s_ (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): [Female], 40658, 57.6 gm. (July 11), 5 km. S Champoton; [Female], 40657, ovary 10 5 mm., 59.8 gm. (July 25), Cenote Seco, 2 km. E Chichen-Itza.

_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 Escarcega had enlarged (probably regressing) testes and indicates breeding later than May.

Specimens (3): [Male], 40660, testis 6 3 mm., 32.0 gm. (July 17), and s.e.x? 40661, 33.8 gm., molting--5th primaries ensheathed (July 17), 1 km. N, 13 km. W Escarcega; [Male], 40659, imm., testis 2 1 mm., 27.6 gm. (July 29), Pueblo Nuevo X-can.

_Pitangus sulphuratus guatimalensis_ (Lafresnaye): Great Kiskadee.-- Apparently our specimens, which were in the late stages of breeding, are the first evidence of reproduction for the species on the peninsula.