Wetland Drainage Research Articles

Range Changes of Birds in the Great Lakes Region

Many changes have taken place in the ranges of bird species in the Great Lakes region during the period of recorded history. These changes were precipitated by various environmental changes in- cluding removal of forest cover, development of farmland, provision of various new cultivated crops, overshooting and drainage of wetlands. Amelioration of the climate has had a decisive influence on the range changes of some species. Protection has prevented the extinction of some species and it has accelerated the spread of other species. This paper deals with native breeding species only and is a review of the literature. Four species have completely disappeared from the region. Only one extension of range in a southward direction is known, but this is a re- occupance of formerly inhabited range. At least 10 species have a well- documented spread of range in a northerly direction, while there is some circumstantial evidence of a similar spread of several other species. Ten species have displayed a definite spread in an easterly direction, and there is strong evidence that at least eight more species spread in that direction. Two species have spread their range in a westerly direction. Range restrictions are known for at least two species. Four species have reoccupied former habitat.