Since the 1979 publication of this book much has been learned of breeding bird distributions in North America, largely as a result of the national Breeding Bird Surveys that were initiated in the 1960s and have continued to the present (Sauer, Hines and Fallon, 2008). From these studies long-term regional average densities of breeding birds have been deduced and national maps generated (Patuxent Wildlife Research Center. 2003). There have also been several state-wide studies on breeding birds of the Great Plains, as represented by breeding bird atlases for South Dakota (Peterson, 1995), Nebraska (Mollhoff, 2001), Kansas (Busby and Zimmerman, 2001), Oklahoma (Reinking, 2004) and Texas (Benson and Arnold, 2001). There have also been breeding bird atlases produced for the adjoining states of Iowa (Jackson, Thompson and Dinsmore, 1996), Missouri (Jacobs and Wilson. 1997) and Colorado (Kingery, 1998).
Based largely on these sources of information, I have updated most of the more than 300 original range maps appearing in this book, and whenever space allowed have placed the updated versions below the original ones, to allow for easy comparisons. In most of these, inked-in areas are shown to indicate higher population densities. In the updated maps light shading indicates regions used by migrating species. No species has shown any significant southward shifts in their breeding distributions, but many southern species have moved northwardly. Some such northward range shifts have been attributed to global warming (Hitch and Leeberg, 2007). A few species, such as the Red-bellied Woodpecker and Wood Duck, have continued to advance westwardly across the Plains States since the early 1900’s as riparian woodlands have matured into forests, offering new nesting opportunities for these tree-dependent species in originally relatively treeless regions. In some markedly expanding species, such as the red-bellied woodpecker and house finch, the clustered dots on these species’ range maps are not indicative of either the exact number or locations of known nestings.
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