A large, colorful rail with dark purple to blue colors and a large red bill and frontal shield, the Gray-headed Swamphen is a recent addition to the avifauna of North America due to the establishment of a nonnative population in southeastern Florida. Although recently known as the Purple Swamphen (Porphyrio porphyrio), the taxonomy of this species is complex and various taxonomic bodies now spilt the P. porphyrio complex into 6 species, including the Gray-headed Swamphen (P. poliocephalus). For further information on the taxonomy of Porphyrio, see Systematics.
The native range of the Gray-headed Swamphen extends from the Middle East through India and southern Asia to northern Thailand. In 1996, this swamphen was discovered in Florida at Pembroke Pines in Broward County, the result of unintended releases from one or two private collections nearby. The following decade saw the Gray-headed Swamphen expand its range within Southeast Florida, including the Everglades, the Everglades Agricultural Area, and Lake Okeechobee, with dispersers found outside this region. From October 2006 through December 2008, an eradication program by state agencies removed 3,187 swamphens (Hardin et al. 2011). However, the eradication campaign was deemed a failure at reducing the distribution and abundance of swamphens, and was discontinued. Since then, the Gray-headed Swamphen has continued to increase in the region and the species is now a common sight in stormwater treatment areas, water conservation areas, agricultural areas, and constructed wetlands in urban and suburban Southeast Florida. However, range expansion to date has mostly been limited to Southeast Florida.
The Gray-headed Swamphen has received little study in Florida (e.g., Pranty et al. 2000, Hardin et al. 2011, Pranty 2012, Pranty 2013a, Callaghan and Gawlik 2016). As a result, we incorporate into this account information on the Gray-headed and other closely related swamphens (Porphyrio) from the Old World (e.g., see Ripley 1977, Taylor 1996, Taylor 1998). More detailed information was compiled for various sections of this account; e.g., habitat (Taylor 1996, Freifeld et al. 2001), breeding (Craig 1980a, Craig 1980b, Jamieson and Craig 1987a, Jamieson and Craig 1987b, Jamieson 1997, Craig and Jamieson 1988), behavior (Holyoak 1970, Craig 1977), evolution (Garcia-R. and Trewick 2015), and diet (Carroll 1966, Norman and Mumford 1985).
Although the Gray-headed Swamphen is predominantly sedentary within its native range, Porphyrio are known to disperse long distances (> 300 km) in response to unsuitable water levels (e.g., Vielliard 1973, Sánchez-Lafuente et al. 2001), and such dispersal has been documented in Florida (Pranty 2012). Their excellent dispersal ability combined with the abundance of an important food plant in Florida, the Gulf Coast spikerush (Eleocharis cellulosa; Pranty 2013a, Callaghan and Gawlik 2016), has raised concern among wildlife managers about further expansion of the species. As a result, additional research on the potential impacts to native flora and fauna is badly needed.