The Wilson Journal of Ornithology 129(4):771–782, 2017 DIET AND FEEDING BEHAVIOR OF THE HORNED GUAN (OREOPHASIS DERBIANUS) IN MEXICO FERNANDO GONZ ´ ALEZ-GARC ´ IA, 1,2,3,8 EDUARDO SANTANA-C., 4 PEDRO D. JORDANO BARBUDO, 5 VICTOR RICO-GRAY, 6 AND VICENTE URIOS MOLINER 7 ABSTRACT.—The Horned Guan (Oreophasis derbianus) is endemic to humid montane forests of southern Mexico and Guatemala. This species is considered endangered because of their small populations, the loss and fragmentation of habitat, illegal trade, and overexploitation by subsistence hunters. We update information about the species’ diet and foraging behavior by integrating the results generated during two and a half decades of research on the Horned Guan’s ecology at the El Triunfo Biosphere Reserve, in Chiapas, Mexico, with additional published information compiled from other areas. Based on nearly 450 hrs of direct observations of free-ranging guans and 530 discrete feeding events, we found that during the breeding season Horned Guans feed primarily on fruits from six species of plants and leaves from one species. Horned Guans were not observed eating animal matter, corroborating its specialized frugivore-folivore habits. Our study increases the known plant taxa found in the Horned Guan’s diet in El Triunfo from 40 to 63 (Supplemental Material), and globally to 101 species (Supplemental Material). For 48 taxa in El Triunfo, only fruits were consumed, while for eleven taxa consumption was restricted to leaves, and to flowers for one species; for four taxa both fruits and leaves were consumed. We found significant differences between males and females in the location of foraging on trees and diet composition. Young birds are fed fruits of Citharexylum mocinnii and leaves of Solanum appendiculatum by their mothers, both of which are rare in the diet of adult males. The conservation of the Horned Guan requires the long-term protection of suitable habitat that maintains the plant species important in their diet. Received 21 March 2016. Accepted 18 January 2017. Key words: conservation of Neotropical montane forest birds, El Triunfo Biosphere Reserve, foraging behavior, frugivory, Horned Guan, Mexican cloud forest, Oreophasis derbianus. The Horned Guan (Oreophasis derbianus) is endemic to the humid montane forest of southern Mexico and Guatemala (Andrle 1967, Howell and Webb 1995, del Hoyo and Motis 2004). At the global level, the species is currently considered endangered (Brooks 2006, BirdLife International 2015), because of small population sizes and threats from hunting, deforestation, and illegal trade (CONAP 2001, Eisermann and Avenda˜ no 2006, SEMARNAT 2010, BirdLife International 2015, del Hoyo and Kirwan 2015). Although there are many published descriptions of its biology and ecology in the wild and in captivity ( ´ Alvarez del Toro 1976; Gonza ´lez-Garc´ ıa 1984, 1986, 1988, 1991, 1994, 1995, 1997a, b, c, 2001, 2005a, b, 2007, 2009; Gonza ´lez-Garc´ ıa and Bubb 1989; G´ omez de Silva G. et al. 1999; M´ endez 2000, 2010; Gonza ´lez-Garc´ ıa et al. 2001, 2006a, b; Secaira and Cornejo 2003; Montes 2005; Pozo V. et al. 2005; Rivas Romero and C´ obar Carranza 2005, 2007; Rivas-Romero et al. 2005; Secaira 2005; Abundis 2006; Eisermann et al. 2007; Secaira and Cornejo 2007; Tovar et al. 2007, 2009; Cornejo 2009; Dierenfeld et al. 2009; Ramos and Gonza ´lez- Garc´ ıa 2009), important aspects of its ecology are still unknown (e.g., home range and seasonal and patterns of movements). Taxonomically, this species is placed in a monotypic genus, Oreophasis, and individuals have a ‘horn’ (naked coral-red bony structure growing on top of the head). It is one of the few bird species that feeds predominantly on fruits and leaves, as well as nectar and flowers (Klasing 1998, Mu˜ noz and Kattan 2007, Rivas Romero 2008, M´ endez 2010). 1 Red Biolog´ ıa y Conservaci´ on de Vertebrados. In- stituto de Ecolog´ ıa, A.C. Carretera Antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, M´ exico. 2 Departamento de Ciencias Ambientales y Recursos Naturales, Facultad de Ciencias, Universidad de Alicante. Carretera San Vicente del Raspeig s/n, San Vicente del Raspeig, Alicante, 03690, Spain. 3 Centro Interdisciplinario de Investigaci´ on para el Desarrollo Integral Regional Unidad Oaxaca (CIIDIR), Instituto Polit´ ecnico Nacional, Calle Hornos 1003, Col. Santa Cruz Xoxocotla ´n, C.P. 71236. Oaxaca, M´ exico. 4 Instituto Manantla ´n de Ecolog´ ıa y Conservaci´ on de la Biodiversidad. Departamento de Ecolog´ ıa y Recursos Naturales, Centro Universitario de la Costa Sur, Uni- versidad de Guadalajara. Av. Independencia Nacional 151, Autla ´n de Navarro, Jalisco, M´ exico. 48900. 5 Estaci´ on Biol´ ogica de Do˜ nana, CSIC, Isla de la Cartuja, Avda. Americo Vespusio S/N E-41092, Sevilla, Spain. 6 Instituto de Neuroetolog´ ıa, Universidad Veracruzana. Av. Luis Castelazo Ayala s/n. Col. Industrial Animas. Xalapa, Veracruz, 91190 M´ exico. 7 Universidad de Alicante. Campus San Vicente del Raspeig, Edificio Ciencias III, Alicante, 03080 Spain. 8 Corresponding author; email: fernando.gonzalez@inecol.mx 771