For 32 years, Cruz Monroy has walked the streets of a small town on the fringes of Mexico’s capital with a tower of small cages filled with birds, turning daily errands into a moving soundscape of red cardinals, green and blue parakeets and multicolored finches. The birdsongs, Monroy said, bring people joy as he carries them from his home and cares for and raises the birds there.

In Mexico, the men who do this are known as pajareros, or street bird vendors, and the practice—selling birds in stacks of cages—goes back generations. AP reported that the sellers have long been fixtures in Mexican markets and are among an estimated 1.5 million street vendors working on the country’s streets.

During Palm Sunday, that routine takes on a public, religious centerpiece: hundreds of pajareros gather in Mexico City and decorate cages for a procession. AP said the vendors adorn “10-foot-tall stacks of cages” with bright flowers, tinsel and images of the Virgin of Guadalupe, Mexico’s patron saint, then walk miles through the capital with their families to the city’s iconic basilica.

But Monroy said that the visibility of pajareros in recent years has declined. AP reported that pajareros have slowly disappeared from the streets amid mounting restrictions by authorities and sharp criticisms from animal rights groups that describe the practice as abuse and trafficking.

Monroy and other vendors say they do not capture birds in ways they say would violate rules—AP reported that they argue tropical species are “wild birds, not pets” under Mexican authority messaging—and that they often breed the birds they own themselves while taking care of the animals. Even with that defense, Monroy said the tradition is dying out within his own family and community.

In the face of harassment by authorities and criticism, Monroy said he wants his children to find more stable work than street vending. “Because of the restrictions, harassment by certain authorities, many friends have left selling birds behind,” he said. “For my children, it’s not stable work anymore. We have to look for other alternatives.”