Interspecific brood parasitism in galliform birds

Mode of development in birds helps determine the form of brood parasitism a species exhibits. Most knowledge of precocial brood parasites comes from a single avian family, the waterfowl (Anatidae: Anseriformes). Here we review cases of interspecific brood parasitism (IBP) in a second group of precocial birds, the order Galliformes. IBP is uncommon but taxonomically widespread, occurring in at least 11 species and in four of five galliform families. By far the most common brood parasite is the Ring-necked Pheasant Phasianus colchicus. Hosts were generally other ground-nesting precocial species. It is unclear whether the absence of IBP in the Cracidae (Guans, Curassows, and Chachalacas) is due to the paucity of research on tropical gamebirds or because tropical birds such as the Cracidae may be less likely to practise IBP. Galliform birds mirror the trend found in ducks in which virtually all species that parasitize heterospecifics are also conspecific brood parasites (CBP). This association supports the hypothesis that IBP as an adaptive tactic or strategy may evolve from CBP. Alternatively, or additionally, egg-dumping may represent reproductive error on the part of females, such that concordance between CBP and IBP could be a byproduct of having sufficient knowledge of breeding biology only for a subset of galliform species.