Patterns of fecal steroids associated with reproduction in two Cracidae species: the blue-throated piping guan (Pipile cumanensis cumanensis) and the horned guan (Oreophasis derbianus)

Abstract

Guans, curassows, and chachalacas (family: Cracidae) are large-bodied, arboreal birds native to tropical and subtropical Central and South America. Currently, 51 species are recognized, and many are listed by the IUCN as vulnerable or endangered.  This study describes endocrine patterns associated with reproduction in two guan species, the blue-throated piping guan (Pipile cumanensis cumanensis) and the horned guan (Oreophasis derbianus). Fecal samples were regularly collected from 7 female and 6 male piping guans, and from 2 female and 1 male horned guan. Concentrations of fecal estrogens, progestagens, and androgens were quantified using commercially available immunoassays. Concentrations of fecal estrogens and progestagens consistently rose prior to egg-laying for both piping and horned guans. Fecal androgen concentrations of male piping guans varied by month, with the highest values measured from July to November. The male horned guan showed three sustained increases in fecal androgens during the breeding season, one prior to egg-laying and two subsequent rises coinciding with egg-laying by his mate. This study provides the first endocrine data for guans and confirms that fecal hormone analysis is an effective way to monitor reproduction, including egg laying and seasonal changes in steroid levels.