The species was closely related to the western clade of the great-tailed grackle, from which it diverged quite recently, around 1.2 million years ago.

Early observations recorded by Franciscan friar Bernardino de Sahagún in the 16th-century manuscript General History of the Things of New Spain indicate that the species was found in cultivated areas and towns.

Several records of the slender-billed grackle are known from three different habitats, such as wetlands, cultivated plots, and human settlements.

When the initial European settlers came to central Mexico, they observed that the Aztecs targeted the slender-billed grackle; the reason for this is partially unclear.

[3] The slender-billed grackle is believed to have become extinct around the turn of the 20th century, after disappearing from the Valley of Mexico.

Reports of grackles nesting in urban areas also exist, but this is believed to have been a response to the loss of habitat due to the conversion of marshes to farmland.