The slender-billed grackle (Quiscalus palustris ) was a species of grackle in the Icteridae (New World blackbirds) family of birds. The species was closely related to the western clade of the great-tailed grackle, from which it diverged quite recently, around 2,000 years ago.
The slender-billed grackle was endemic to central Mexico, especially in the Valley of Mexico and the Toluca Valley. 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. Later records indicated that it might be a marsh specialist. The species became extinct around the turn of the 20th century.
The slender-billed grackle was originally known from the Rio Lerma area in Mexico. It has not been recorded since 1910. Several records of the slender-billed grackle are known from three different habitats, such as wetlands, cultivated plots, and human settlements. Slender-billed grackles inhabited marshes and borders of the lakes. Emergent aquatic vegetation was commonly used for nesting material by the slender-billed grackles.
The slender–billed grackle usually nested in marshes and aquatic vegetation; however, as the population in Mexico increased, the species was able to adapt to the changes in the environment and learned to nest in towns and cultivated plots. The slender-billed grackle hatched its eggs in reeds.
