Tom says. . .

Sandhill Cranes, being grey in color, can hide more effectively during the nesting season.

The biggest reason for the success of the Sandhills is the habitat they use. Sandhills feed mostly on seeds and insects and find lots of both items in agricultural fields. They love grain, including crops such as corn and milo. Whooping Cranes are much more aquatic, spending their entire summer and winter in wetlands. When the U.S. became settled, most of the wetlands were drained and turned into agricultural fields.

Replacing wetlands with agricultural fields provided more food for Sandhills, but actually took away habitat from Whooping Cranes. Thus, Sandhills increased in number whereas the number of Whooping Cranes — once as numerous as 10,000 in North America — declined to no more than 1,400 birds by around 1870 and fell to an all-time low of 21 birds in 1941.