Part 4

Charadrius alexandrinus tenuirostris (Lawrence): Snowy Plover.--This was one of the commonest shorebirds on the beaches and mudflats west of Sisal. Several immature birds were taken, along with a pair of half-grown chicks, indicating the species was breeding, or recently had bred, there. No previous record of this species breeding on the peninsula has been found.

Specimens (6): [Female], 40431, ovary inactive, 38.2 gm. (August 7), 4 mi. S Sisal; , 40426 testis minute, 35.4 gm. (August 9), [Female], 40427, half-grown chick, 25.4 gm. (August 9), , 40428, half-grown chick, 21.2 gm. (August 9), [Female], 40430, imm., 38.0 gm., little fat (August 10), [Female], 40429, ovary inactive, 35.7 gm., little fat, molting--1st through 6th primaries and middle pair of rectrices are new (August 10), all from 13 km. WSW Sisal. Mallophaga: Actornithophilus ochraceus, August 9; Quadraceps assimilis major, August 7.

Charadrius wilsonia wilsonia Ord: Wilson Plover.--A flock of about 11 was seen on the beach north of the village on Isla Mujeres on August 1. Two specimens were collected on the leeward side of the island about three kilometers south of the village on August 2. The only evidence of breeding was slightly enlarged testes in one male. Two individuals were sighted on the east coast of the mainland at Puerto Juarez on August 4. The species was common 3 to 13 km. west-southwest of Sisal; specimens taken there may have been migrants.

Specimens (5): , 40435, testis 3 × 1 mm., 59.0 gm. (August 2), and [Female], 40436, ovary inactive, 49.3 gm. (August 2), Isla Mujeres; [Female], 40434, ovary inactive, 53.6 gm. (August 7), , 40433, testis 1 mm., 54.5 gm. (August 9), and , 40432, imm., 53.7 gm., little fat (August 11), 3-13 km. WSW Sisal. Mallophaga: Quadraceps assimilis major, August 2 and August 11.

Actitis macularia (Linnaeus): Spotted Sandpiper.--A total of six individuals was seen on Isla Mujeres; each was alone. The species was common at Sisal where it was often seen in small mixed flocks with Snowy Plovers and Wilson Plovers.

Specimens (3): , 40437, testis 2 × 1 mm., 33.8 gm. (August 9), , 40438, imm., 28.2 gm. (August 10), and sex? 40439, imm., 31.0 gm. (August 10), 13 km. WSW Sisal. Mallophaga: Quadraceps ravus; August 10.

Catoptrophorus semipalmatus inornatus (Brewster): Willet.--A flock of 15 or 20 individuals was seen almost every day of our stay on the beach 8-13 km. WSW of Sisal. Measurements of two of the specimens are large and they are clearly referable to C. s. inornatus.

Specimens (3): , 40441, testis 3 mm., 242.3 gm., wing 205 mm., tail 80 mm., tarsus 66 mm., culmen (from feathers) 60 mm. (August 9), [Female], 40440, ovary inactive, 240.5 gm., wing 204 mm., tail 77 mm., tarsus 69 mm., culmen (from feathers) 59 mm. (August 11), and , 40442, imm., 221.1 gm. (August 11) 8-13 km. WSW Sisal. Mallophaga: Austrominopon sachlebeni, August 9; Quadraceps carrikeri, August 11.

Arenaria interpres (Linnaeus): Turnstone.--Six individuals were sighted on Isla Mujeres on August 1 and one individual was sighted 4 km. W Sisal on August 11.

Crocethia alba (Pallas): Sanderling.--This species was relatively common at Sisal where several flocks of 30 to 40 birds were seen. One specimen (40444) shows an unusual pattern of molt; replacement of outer primaries has preceded that of the inner.

Specimens (4): , 40445, testis 3 × 1 mm., 57.5 gm., heavy fat (August 9), [Female], 40444, ovary granular 6 × 3 mm., 56.7 gm., molting (August 11), , 40443, 35.5 gm. (August 11), and [Female], 40446, imm., 54.1 gm. (August 11), 6-1/2-13 km. WSW Sisal. Mallophaga: Lunaceps holophaeus actophilus, August 11; Carduiceps zonarius, August 11.

Ereunetes pusillus (Linnaeus): Semipalmated Sandpiper.--The only individual seen was taken from a mixed flock of Sanderlings and Wilson Plovers.

Specimen (1): , 40447, testis minute, 24.4 gm. (August 11), 8 km. WSW Sisal.

Himantopus mexicanus (Müller): Black-necked Stilt.--A lone individual was sighted on Isla Mujeres on August 2. A pair was on the mudflats among mangroves at Sisal, of which the male was taken on August 7. Although Paynter (1955a) indicated that this species probably breeds on the peninsula, there are no definite breeding records. Our specimen had only slightly enlarged testes, but its close association with a female suggested that the pair may have been mated.

Specimen (1): , 40448, testis 7 × 3 mm., 189.4 gm., little fat (August 7), 5 mi. SW Sisal.

Larus atricilla Linnaeus: Laughing Gull.--This species was seen regularly along the coasts of the peninsula.

Specimen (1): [Female], 40449, ovary 7 mm. (inactive), 253 gm. (August 7), 4-3/10 mi. W Sisal. Mallophaga: Quadraceps sp.

Sterna albifrons antillarum (Lesson): Least Tern.--A flock of about 20 individuals was seen on Isla Mujeres; two individuals were shot and appear to be the first specimens from the island.

Specimens (2): [Female], 40451, ovary slightly enlarged, 49.0 gm. (August 2); sex? 40450, 41.8 gm. (August 2), Isla Mujeres.

Thalasseus sandvicensis (Latham): Cabot Tern.--Lone individuals were seen several times flying along the coast southwest of Sisal.

Specimen (1): , 40452, 186 gm. (August 11), 13 km. WSW Sisal. Mallophaga: Saemundssonia brevicernis.

Patagioenas flavirostris flavirostris (Wagler): Red-billed Pigeon.--This species was seen at all stations except on the islands and in the arid scrub at Sisal. It was especially abundant at Escárcega, Felipe Carrillo Puerto, and Puerto Juarez. The male in breeding condition suggests that the breeding season extends into the summer.

Specimens (5): [Female], 40455, ovary inactive (July 13), [Female], 40456, ovary inactive, (July 13), and , 40457, testis 7 × 5 mm. (July 15), 6-{7-1/2} km. W Escárcega; , 40453, testis 15 × 6 mm., 225.5 gm. (August 16), and [Female], 40454, ovary inactive, 228 gm. (August 16), 4 km. NNE Felipe Carrillo Puerto. Mallophaga: Columbicola sp., July 15.

Zenaida aurita yucatanensis Salvadori: Zenaida Dove.--This species was common at Sisal.

Specimens (3): [Female], 40459, imm., 136.5 gm., little fat (August 11), 8 km. SW Sisal; [Female], 40399, 151.2 gm. (August 7), 1-1/2 mi. S Sisal; [Female], 40400, 163.3 gm. (August 18), 2 km. WSW Sisal. Mallophaga: Columbicola macrouras, August 7.

Zenaida asiatica Linnaeus: White-winged Dove.--Birds of this species were ubiquitous in the scrub west of Sisal between 10 a.m. and 4 p.m. but inconspicuous at other times. Apparently the birds were from nests, roosts, and watering sites in the taller forest inland.

Columbina passerina pallescens (Baird): Common Ground Dove.--This species was common at almost all collecting localities, but was always outnumbered by the Ruddy Ground Dove. The species was not seen in the vicinity of Escárcega, probably because of the tall forest and lack of clearings there.

Specimens (5): , 40461, testis 10 × 5 mm., 40.9 gm. (August 10), 2 km. WSW Sisal; , 40460, testis 6 × 3 mm. (August 9), and [Female], 40464, ova to 4 mm., 37 gm. (August 9), {3-1/2}-4 km. N San Miguel, Isla Cozumel; [Female], 40463, imm., molting, 35.5 gm. (August 15), 4 km. NNE Felipe Carrillo Puerto.