Hanging clusters of gourd birdhouses for the purpose of attracting purple martins is an Alabama folk tradition, according to the blog Appalachian History.
Choctaw and Chickasaw gardeners began the practice. The purple* martins would eat damaging insects and mosquitoes and drive away crows and blackbirds from the corn.
Farmers of European and African origins later adopted the custom, particularly as the birds also protect chickens by scaring away hawks.
The gourds should be hung in groups of 10 or more, according to the National Wildlife Federation’s blog. They should also swing from crossbars and wires on poles at least two-stories high.
*They are actually dark blue and black, or pale grey.