As I discussed in a post back in February, 2007 (see Settlers and Cardinals), northern cardinals were limited to the southern tier of States until white settlers colonized the Continent. Clearing forest for lumber and agriculture, humans enticed cardinals northward since they favor brushy woodland borders; today, these colorful birds inhabit the eastern and central portions of North America, from southern Canada to Mexico, and have spread through the Desert Southwest into California.
Here in Colorado, northern cardinals began to turn up along the South Platte, Republican and Arkansas Rivers over the past fifteen years or so, moving up these riparian corridors from the Great Plains. In recent years, small populations have become established in towns along those river valleys and an increasing number of individuals and pairs have been making an appearance along the base of the Front Range. Clearly, northern cardinals, currently classified as uncommon local residents in Colorado, are here to stay and, within a few more decades, will likely be common residents across the Front Range urban corridor.
Ever since our earliest ancestors left the African forests to inhabit open grasslands, humans have had a significant impact on other species. In many cases, we have threatened species via overhunting or by destroying their natural habitat while, in others, we have favored their dispersal by creating habitat (e.g. farms, suburbs, skyscrapers) that serve their needs. In the case of northern cardinals, human activity has greatly expanded their range.
