Geographic distribution, or range, is a fundamental demographic feature of a species that in part provides information on habitat use and species viability (Kruger and Radford 2008). Yet knowledge about distribution is often lacking, due mainly to the logistics of documenting the temporal dynamic of a species' distribution (Gaston 2003). Indeed, many published range maps provide inaccurate accounts of current distribution of raptor species (Fuller 1996, Rosenfield 2006). Recent changes in distributions of many species have resulted from large-scale human alterations of landscapes due to urbanization and/or climate change (e.g., Root et al. 2003, Miller-Rushing et al. 2008).

The Merlin (Falco columbarius) was reported as a scattered breeder across the northern portions of the lower 48 United States (Cade 1982, Warkentin et al. 2005). Recently all three Merlin...