The Condor974 15-426 0 The CooperOrnithological Society 1995 REPRODUCTIVE BIOLOGY AND VOCALIZATIONS OF THE HORNED GUAN OREOPHASIS DERBIANUS IN MEXICO ’ FERNANDO GONZALEZ-GARCIA Institute de EcologiaA.C., Apartado Postal 63, Xalapa, Veracruz,C.P. 91000 Mfixico Abstract. Reproductive biology and vocalizations of the Horned Guan (Oreophasisder- bianus)were studied in the El Triunfo BiosphereReserve in Chiapas, Mexico. The nest and eggsare described here for the first time. The Homed Guan apparently has a polygynous mating system. Males make at least five different kinds of vocalizations. Females produce seven or eight different types of calls, which are guttural compared with those of males. One female took 2.81 (k-0.40) incubation recessesdaily during 16 days of observation, and individual recessesaveraged 32.9 (+ 13.1) min. Incubation sessionsaveraged 191 min * 44.6. The incubation period was estimated to be 35-36.5 days. Likely predators of Homed Guan eggsare described. Suggestionsfor the conservationof this speciesand its habitat are presented. Key words: Oreophasisderbianus; vocalizations:mating system;Cracidae; cloud forest; Chiapas. Resumen. Se estudio la biologia reproductiva y vocalizacionesde1 Pav6n (Oreophasis derbianus)en la reservade la biosfera El Triunfo, Chiapas.El nido y 10shuevos son descritos por primera vez. Las observacionesde campo sugierenque el sistema social de esta especie estb basado en la poliginia. Los machos emiten cinco diferentes tipos de vocalizacionesy las hembras de siete a echo, las cuales a diferencia de 10s machos, son todas guturales. Durante la incubation una hembra realiz6 2.8 1 (t-0.40) recesosdiarios durante 16 dias de observation y en promedio cada recesofue de 32.9 (? 13.1) min. Las sesionesde incubation promediaron 191.13 ? 44.60 min. El period0 de incubation se estimo de 35-36.5 dias. Se mencionan a 10sprobables depredadores. Finalmente, se mencionan algunasestrategias para la conservaci6nde la especie. Palabras clave: Oreophasis derbianus: vocalizaciones;sistema social; crhcidos;bosque mesdjilode montaiia; Chiapas. INTRODUCTION This species occurs only in Guatemala and The few previous studies of the Homed Guan Mexico. In the latter, it is limited to the highlands (Oreophasis derbianus) focused on description, of the Sierra Madre in Chiapas and possibly east- taxonomy, and distribution (Salvin and Godman em Oaxaca (Estudillo 1979, Binford 1989, Collar 1902, Ridgway and Friedmann 1946, Fried- et al. 1992). The habitat of this species,montane mann et al. 1950, Vaurie 1968, Delacour and broadleaf or cloud forest, has a restricted distri- Amadon 1973, Blake 1977). Studies which treat bution in Mexico (Rzedowski 1978, Leopold more of its biology are those by Wagner (1953) 1950, Pennington and Sarukhan 1968) and is Andrle (1967), Parker et al. (1976) Alvarez de1 disappearing at an increasing rate as these forests Toro (1976) and Gonzalez-Garcia (1984, 1986, are felled for agriculture, animal husbandry, lum- 1988a, 1988b, 1994). Data on reproduction and ber and coffee plantations (Veblen 1976, Collar vocalizations are scarceand the nest and eggsof et al. 1992). the Homed Guan have remained unknown. Be- In this paper, I present observations on the cause this speciesis in danger of extinction due breeding biology and vocalizations of the Homed to habitat destruction and hunting pressure(Col- Guan, and also discussaspects of its conserva- lar et al. 1992) knowledge of its nest, eggs,and tion. behavior is of critical importance. STUDY AREA AND METHODS The El Triunfo BiosphereReserve (Diario Oficial de la Federation, 13 March, 1990) consists of I Received 1 June 1994. Accepted 19 January 1995. five core areas and a buffer zone which together I4151 416 FERNANDO GONZALEZ-GARCiA Angel Albino Corzo Core Areas Buffer Zone V Mapastepec .“...l. .. ..~-.. ;(/‘ ITZI. .. P... ’ .. ..- Reserve Boundary INSTITUTE OF NATURAL HISTORY ..j‘ osx,m STATE 0F CHIAPAS FIGURE 1. The El Triunfo BiosphereReserve, Chiapas, Mexico. The studysite is locatedin corearea I. have an area of 119,000 ha (Fig. 1). The Reserve pulifolius, Drymis granadensis var. mexicana, includes parts of the municipalities of Acacoy- Podocarpusmatudae, Ulmus mexicanum, Tern- agua, Angel Albino Corzo, La Concordia, Ma- stroemia lineata, Oreopanax sanderianus, 0. pastepec, Villa Corzo, Pijijiapan and Siltepec. capitatus, 0. xalapensis, Nectandra sp. Ocotea The study site is located in core area I, which chiapensis,0. matudai, 0. uxpanapana, Phoebe has an area of 11,594 ha and elevations between siltepecana, P. bourgeviana, Clethra lanata, C. 700 and 2,500 m. It contains five main vegeta- matudae, C. pachecoana. Shrubs and herbs are tion types: tropical evergreen forest, pine-sweet- representedby Cavendishiasp., Centropogonspp., gum forest, coniferous forest, and lower and up- Mconia glaberrima, Senecio sp., Clusia mexi- per cloud forests.The study area is in the upper cana, Rondeletia piramidalis, Malviscus arbo- cloud forest at an elevation of 1,850 to 2,100 m. reus, Gentlea tacanensis, Fuchsia speniculata, This forest is dense,with broad-leaved evergreen Ardisia spp., and Chamaedorea spp. Ferns are trees 20 to 30 m in height and some individuals abundant, including tree ferns (Cyaihea jiilva) even taller. which reach heights of up to 15 m. Bromeliads The dominant tree speciesin the cloud forest (e.g., Tillandsia ponderosa, T. vicentina, Vriesea are: Matudaea trinervia, Quercusoocarpa, Hed- breedloveanaand orchids (e.g., Epidendrum dif- yosmum mexicanum, Ocotea spp., Conostegia forme, Maxilaria praestans,Odontoglossum cor- volcanalis,Amphitecna montana, Symplococar- d&urn) are also abundant (Gonzalez-Garcia 1984, pon flavifolium, Calyptranthessp., Glossostipula Ramirez and Gonzalez-Garcia, unpubl. data). concinna, Eugenia malensis and Zunila cucul- Data collected by the author in 1983 indicate lata (Williams 199 1, Ramirez and Gonzalez- that the maximum daily temperature averages Garcia, unpubl. data). The following tree species 15°C and the minimum daily temperature av- are also common: Dendropanax pallidus, D. po- erages5°C but temperatures down to -2°C have HORNED GUAN IN MEXICO 417 been recorded. There is a relatively dry season Percent times spent in each area and during from March to May, although rain can be abun- each recesswere compared with a Kruskal-Wal- dant throughout the year. Average annual pre- lis test (Zar 1984). A simple linear regressionwas cipitation exceeds 3.3 m. Strong winds, origi- used to test for significant differences in total nating in the Gulf of Mexico and Pacific Ocean, daily recesstime during 16 complete days of ob- are common in autumn and winter. Mist is com- servation (Sokal and Rohlf 1979, Zar 1984). mon throughout the year. Frost occursfrom Jan- Birds were observed using 10 x 40 binoculars. uary to March. Vocalizations were recorded with a Uher 4000 This study was carried out over a period of tape recorder and parabolic reflector (recordings eight months (February to May 1982 and Feb- are deposited in the author’s sound library). A ruary to May 1983) and supplemented in 1984. chronometer was used to measure the length and Daily observations ranged from 30 min to 11.5 timing of vocalizations as well as the time spent hr. Total observation time during the study was by the females during incubation sessionsand 842 hr. recesses. At the beginning of February 1982, I made a walking survey of core area I, taking advantage RESULTS of establishedtrails, to determine sitesfrom which These observations are based mainly on the be- the Horned Guan could be observed and re- haviors of one male (referred to hereafter as “the corded. Once the first individuals were located, male”) and three or four females which were efforts were focused on following the birds to found in the same area in 1982, although data record their behavior continuously. Two blinds are included on some of the 23 additional in- were built to observe a nest and a dust bath. dividuals (12 solitary adult males, four “pairs,” Detailed observations were made of morpholog- and three young individuals) observed in other ical and plumage characteristicsin order to dis- trails of the reserve. tinguish individuals. To determine the age of Sexual dimorphism. Without the aid of vo- young individuals, particular attention was paid calizations and behavior, the sexescannot be re- to the size and development of the horn for com- liably separated under field conditions. How- parison with data published by Alvarez de1Toro ever, in the hand the lengths of horn, wing, tail (1976)andGonzalez-Garcia (1986, 1988a). Nests and tarsus of males average longer than those of were located by following the incubating females. females (Vaurie, 1968). On the majority of oc- The polygynous mating system was deter- casions when it was possible to compare adult mined by using characteristics which differed males and females directly, the difference in horn among the individuals. One male was identified size was slight. In only two pairs (out of the seven by the presenceof an incomplete feather in the or eight observed) was this difference easily not- center of his tail. Females were distinguishedfrom ed, in one pair the horn of one male was esti- the male by their calls and from each other by mated to be approximately 6 cm long (well-de- the following characteristics:Female 1, discon- veloped adult), while that of the female was ap- tinuous white band on the tail; Female 2, dis- proximately 3-4 cm. This difference in horn size continuous white band on the tail (probably same