CHECK-LIST OF COLORADO BIRDS
The following list includes all the species and varieties, so far as known to naturalists, occurring in the State of Colorado. Of course, these birds as families are not restricted to that State, and therefore the catalogue comprehends many of the species to be found in adjacent and even more remote parts of the country. Aside from the author's own observations, he is indebted for a large part of the matter comprised in this list to Professor Wells W. Cooke's pamphlet, entitled, "The Birds of Colorado," with the several appendixes, and to the invaluable manuals of Mr. Ridgway and Dr. Coues.
According to the latest information accessible to the writer, 389 species and varieties occur in Colorado, of which 243 are known to breed. This is a superb record, and is excelled by only two other States in the Union, namely, Texas and California. Colorado's splendid list is to be explained on the ground of its wonderful variety of climate, altitude, soil, and topographical features, such as its plains, foothills, lower mountains, and towering peaks and ranges, bringing within its boundaries many eastern, boreal, middle western, and far western forms.