Summer Birds From the Yucatan Peninsula.

by Erwin E. Klaas.

INTRODUCTION

Because its unique geographical location and ecological setting supports a rich and varied avifauna, the Yucatan Peninsula has received considerable attention by ornithologists. The most valuable contribution is Paynter's "The Ornithogeography of the Yucatan Peninsula" (1955a), an authoritative study of the composition, distribution, and origin of the avifauna of the region. His work contains a complete listing of all species reported to that time from the peninsula. It considers the hundreds of specimens collected by the author and his a.s.sociates during many months of field work, provides a synthesis of all the information available to 1955, and is the basic reference to the avifauna of the area. Paynter also pointed out matters for which information is lacking. Two of the most conspicuous deficits that he noted are the lack of knowledge about many species that occur on the peninsula in summer, and the paucity of data as to time of breeding, although some information on reproduction in a few species was published subsequently by Paynter (1955b) and Storer (1961).

In July and August of 1962, I was a member of a field party from the Museum of Natural History, The University of Kansas, engaged in a survey of vertebrates and their ectoparasites on the Yucatan Peninsula.

The purpose of the present paper is to report on the birds collected and observed during the course of this field work. Particular emphasis is given to breeding information, but observations concerning distribution, incidence, and molt also are given. In addition, a list of the chewing lice (Mallophaga) taken from various specimens is given in Table 2 and in the appropriate species account of the host. Other ectoparasites removed from these birds will be reported on elsewhere.

ACKNOWLEDGMENTS

I am especially indebted to Dr. J. Knox Jones, Jr., under whose direction this field study was undertaken, and to Dr. Richard F.

Johnston who aided greatly in the identification of specimens and critical reading of the ma.n.u.script. I am grateful also to other members of the field party who helped in collecting many of the specimens reported herein: Ticul Alvarez, A. Binion Amerson, Dr. William E.

Duellman, Dr. J. Knox Jones, Jr., Thomas E. Lovejoy, III, Jack G.

Makepeace, Dwight R. Platt, William C. Stanley, Jerome B. Tulecke, and John Wellman. Dr. K. C. Emerson graciously identified the specimens of Mallophaga and Dr. Allan R. Phillips aided in identification of some of the birds.

In addition, I wish to express sincere thanks for quarters provided our field party at the Campo Experimental Forestal "El Tormento" at Escarcega, Campeche, by Ing. Hector Flores S.; at Pueblo Nuevo X-can, Quintana Roo, by Pablo Alimilla; at Felipe Carrillo Puerto, Quintana Roo, by Fernando Esquival Montono; and at Piste, Yucatan, by Luis V.

Polanco. The field party benefited also from arrangements and helpful suggestions made by Eduardo C. Welling of Merida and Marynoll Father Joseph Early of Felipe Carrillo Puerto. Wherever we camped the local Mayans were exceptionally helpful, especially as guides and collectors.

Our field party was composed of two units. One unit, working on a survey of Middle American vertebrates and their ectoparasites, was supported by the United States Army Medical Research and Development Command (Contract No. DA-49-193-MD-2215). The second unit, composed of students in the Field Course in Vertebrate Zoology from The University of Kansas, was supported in part by the Museum of Natural History and by a grant from the National Science Foundation (G 20939, Special Projects in Science Education). The late Ing. Luis Macias Arellano, Departamento de la Fauna Silvestre, Direccion General de Caza, Mexico, D.F., generously provided the necessary permits for collecting vertebrates.

PHYSICAL FEATURES

The Yucatan Peninsula is a northeastern projection of Central America lying between the Gulf of Campeche, the Gulf of Mexico, and the Caribbean Sea. Its area is approximately 143,500 square kilometers and includes the Mexican states of Campeche and Yucatan and the spa.r.s.ely settled Territory of Quintana Roo, plus parts of British Honduras and the Peten region of Guatamala. The peninsula has a mean breadth of about 300 kilometers and a coast line of about 1100 kilometers.

Topographically, the peninsula is a low-level plain that rises gradually inland to the south. The coast on the north and west is low, sandy, and semi-barren; openings through the outer coastal strand lead to narrow brackish lagoons surrounded by mangroves. The eastern coast consists of bluffs, indented with bays and bordered by several islands, the largest being Cozumel. A small range of hills traverses the peninsula from the city of Campeche to Chetumal Bay; although appearing sizeable, these almost nowhere exceed 100 meters in elevation. The extreme southerly portion of the peninsula is moderately hilly and is covered with tropical rain forest.

The peninsula is composed almost wholly of a bed of coraline and porous limestone covered with a layer of thin, dry soil formed from the slow weathering of the bedrock. The humus is rarely more than a few centimeters deep, and consequently cornfields (_milpas_) must be moved every two or three years. With each move a new area of the land is cleared and burned. This agricultural practice has been routine with the Mayan people for centuries and apparently has had a profound effect on the vegetation, severely limiting the extent of virgin forest.

In many places, especially in the northern part of the peninsula, the rocky surface of the terrain is perforated by natural wells or sink-holes, which are called _cenotes_ locally. Many _cenotes_ support small "islands" of unique vegetation, the composition of which somewhat resembles the rain forest of the southern part of the peninsula.

Temporary water-holes and shallow lakes (_aguadas_) are spa.r.s.ely scattered throughout the southern half of the peninsula. There are no rivers of importance; most that are present are in the southernmost region.

The climate of northern Yucatan is hot and dry, and the absence of high mountainous ridges to intercept the moisture-bearing clouds from the Atlantic accounts for less rain than would be expected. The southernmost part of the peninsula receives a maximum of 200 centimeters of rain annually. The amount decreases toward the north to an average of about 45 centimeters. Almost all of the rain falls from May to October. Daily temperatures range from 78 to 98 F. in the shade; cool sea winds prevail day and night throughout most of the year. The hottest months are May and June. In winter, fierce northers, _temporales_ or _nortes_, occasionally sweep across this open region, bringing rain and cooler temperatures, lasting several days.

The areas adjacent to British Honduras and Guatemala receive sufficient rainfall to support forests containing mahogany (_Swietenia_); sapodilly (_Achras_); several valuable cabinet woods; logwood (_Haematozylon_) and other dyewoods. As one proceeds northward the flora and fauna change gradually from that of the wet tropics to that of the dry tropics.

Paynter's (1955a) system of vegetational zones on the peninsula is useful to ornithologists. He recognized three zones: Scrub, Deciduous Forest, and Rain Forest. The Scrub zone occupies Isla Holbox and Isla Mujeres and the arid northern coast of Yucatan. The zone extends only a few miles inland and consists of low-tropical thorn forest of mesquite (_Prosopsis_), _Mimosa_, _Yucca_, _Agave_, and mangrove (_Rhizophora_) wherever standing water occurs. Sisal in Yucatan and Isla Mujeres of Quintana Roo are in this Scrub zone.

The Deciduous Forest zone is a vast area of low, semiarid, secondary forest occupying all of the state of Yucatan not in the Scrub zone, northern Campeche, and a thin strip a few kilometers wide in Quintana Roo along the Yucatan-Quintana Roo border and a similar narrow band along the eastern coast. The island of Cozumel is also included in this zone. Collections were made in the Deciduous Forest at Champoton, Campeche, Isla Cozumel and Puerto Juarez, Quintana Roo, and Piste, Yucatan.

The Rain Forest zone occupies the remainder of the peninsula and includes most of the territory of Quintana Roo, and the southern half of Campeche. Collections were made in this zone at Escarcega, Campeche, and at Felipe Carrillo Puerto and Pueblo Nuevo X-can, Quintana Roo.

Isla del Carmen cannot be accurately a.s.signed to any of these three zones because most of the island has been planted in coconut palms. It is an area of high rainfall and may once have supported rainforest.

In the present report the term "second growth" refers to areas that have been recently cut over. In these areas, the forest is characteristically low and in a stage of transition. In the Rain Forest zone "second growth" areas usually contain species of deciduous trees.

Paynter (1955a) has given an excellent descriptive summary of the topography, climate, and phytogeography of the Yucatan Peninsula and there is little need to go into further detail here. During summer, the rainy season, the Deciduous Forest is much more luxuriant in appearance than in winter when most of the trees have lost their leaves. Also, the numerous _cenotes_ in this zone support a limited growth of evergreen trees. For example, the large Cenote Seco about two kilometers east of Chichen-Itza contains elephant ear (_Caladium_), mamey (_Mammea_), figs (_Ficus_), and other large trees the trunks of which are some 10 meters below the surface of the surrounding tableland. These plants project five to 10 meters above the surrounding low forest. The floor of this _cenote_ is near the watertable but not below it.

GAZETTEER

The specimens of birds reported herein were collected at the localities shown on the accompanying map (Fig. 1). These localities are listed below in alphabetical order according to states.

Campeche

Champoton.--Lat. 19 21' N, long. 90 43' W, sea level to five meters. A fishing village on the Gulf of Mexico. Collections were made princ.i.p.ally at our camp five kilometers south of the town. Low deciduous forest, second growth, and _milpas_.

Escarcega.--Lat. 18 37' N, long. 90 44' W, elevation 65 meters. A village in southwestern Campeche. Field work was carried out princ.i.p.ally in the vicinity of an agricultural experiment station seven and a half kilometers west of the town. Second growth and moderately tall rainforest.

Isla del Carmen.--Lat. 18 43' N, long. 91 41' W, sea level to two meters. An island in the mouth of Laguna de Terminos. Collections were made at our camp on the northeastern end of the island, about one kilometer southwest of Puerto Real. Coconut plantations and mangrove swamp.

Quintana Roo

Felipe Carillo Puerto.--Lat. 19 35' N, long. 88 02' W, elevation 30 meters. A village in east-central Quintana Roo. Field work was centered at Rancho San Miguel, about four kilometers north-northeast of the village. Mostly second growth rainforest with scattered large patches of tall trees (to 30 meters). Several large _milpas_ were present on the ranch some of which had been recently cleared.

Our camp was at a large aguada bordered on one side by an extensive marsh with tall dense gra.s.s.

Isla Cozumel.--Lat. 20 27' N, long. 86 26' W, sea level to 10 meters. A large island, 15 kilometers east of the mainland.

Collections were made on the northwestern part of the island from one to five kilometers north-northeast of the village of San Miguel in low, dense deciduous forest.

Isla Mujeres.--Lat. 21 12' N, long. 86 43' W, sea level to 30 meters. A small, narrow island about eight kilometers from the coast at the northeastern end of the peninsula. Field work was done on the beach at the northern end of the island, in low deciduous forest in the middle of the island, and in low deciduous forest and cactus (_Opuntia_) a.s.sociation on a high rocky bluff on the southern end of the island.

[Ill.u.s.tration: FIG. 1. A map of the Yucatan Peninsula of Mexico showing localities referred to in the text.]

Pueblo Nuevo X-can.--Lat. 21 52' N, long. 87 26' W, elevation 10 meters. A village five kilometers east of X-can, Yucatan, in rainforest with dense underbrush. Specimens were obtained from the immediate vicinity of the village.

Puerto Juarez.--Lat. 21 10' N, long. 86 49' W, sea level. A small port on the Caribbean Coast with alternating sand beach and limestone sh.o.r.e. Mangrove swamps extend a short distance inland at various points. Specimens were collected in rainforestlike vegetation at a small _cenote_, in low deciduous forest, and at our camp along a large, cleared airstrip four kilometers west-southwest of the village.

Yucatan

Piste.--Lat. 20 42' N, long. 88 28' W, elevation 10 meters. A village in dense, low deciduous forest with many nearby _milpas_.

Collections were made in a wide area in the vicinity of the village, including nearby Chichen-Itza.

Sisal.--Lat. 21 10' N, long. 90 00' W, sea level. A small village on the north-western coast of the peninsula. Collections were made on the beach, in the low scrub vegetation behind the beach, and in the mangrove swamps and nearly-dry lagoons further inland, from three to 13 kilometers west-southwest of the village.