||Changes in the native landscapes of North America have influenced the distribution of many species. The development of a riparian
forest on the Great Plains has provided a corridor for the movement of forest birds across those grasslands that have historically served
as an ecological barrier to dispersal. Almost 90% of the contemporary avifauna of northeastern Colorado was not present at the turn
of the century. The corridor has resulted in secondary contact of many congeneric species which currently hybridize on the Great Plains;
the hybridization may be interpreted either as reversing 10,000 years of speciation, or alternatively as promoting hybrid vigor within
populations. Natural resource management agencies need to develop formal positions on the issues of cosmopolitanism and hybridization
of wildlife species which occur with broad changes in native landscapes.