GPS telemetry reveals occasional dispersal of federally threatened Wood Stork from the Southeastern US to Mexico

Abstract

Wood Storks (Mycteria americana) are iconic wading birds distributed in Latin America as well as in the Southeastern US, where they are federally listed as threatened. Wetlands in the Gulf Coast states are used as post-breeding grounds by some individuals from both the US and the Mexican/Central American populations, and Wood Storks observed east and west of the Mississippi River Basin are generally thought to originate from the Southeastern US and Mexico/Central America, respectively. In the context of a large-scale GPS telemetry study (133 individuals tracked over 14 years), we report the case of two Wood Storks that moved from Georgia and eastern Mississippi, respectively, to Mexico. One of the storks dispersed to Mexico as a juvenile and remained there for the subsequent 4 years into adulthood, indicating permanent settlement. Our findings provide evidence of potential mixing between the US and the Mexican/Central American populations. These movements suggest that mixing between these Wood Stork populations, although probably sporadic, may be a more complex phenomenon than previously thought. While infrequent mixing may still have relevant consequences for gene flow between populations, such low levels of dispersal would most likely not be sufficient to support population replenishment from Mexico/Central America to the US or vice-versa.