From the official website of the Walking Dead comics:
To understand the owl is to understand Santa Muerte (Spanish for Saint Death or Holy Death), who serves as a spiritual icon that millions of people in Mexico (and some in the U.S., Puerto Rico, & Guam) pray to and worship. Typically appearing as a female skeleton in a tunic, the Saint has inspired a death cult of sorts that typically appeals to the disenfranchised (although followers claim she doesn’t discriminate between rich and poor). Some of her worshipers claim she protects them while others use her to cause harm to their enemies (dozens of people have been sacrificed in her name). Known as a vengeful entity, it’s common knowledge that if you ask her for something in life and she delivers, you must give her an offering or suffer the consequences.
The Bronx Journal interviewed botanical store owner Fermin Perez Romero to explain the phenomenon: “What I know about Santa Muerte is that she has been created by God. Her job is to guide us towards God on the last day of our existence.” Muerte’s followers believe death isn’t the end... it’s just a step to eternal life. In Fear the Walking Dead Celia doesn’t think it’s the end for the infected. “(They’re not dead) They are what comes next,” she rationalizes.
Several depictions of Santa Muerte include a globe, scythe, and OWL. According to folk lore, the owl symbolizes her ability to navigate the darkness as well as a messenger from the afterlife. According to Voices of NY, “The myth popular in some Mexican towns that the song of a nocturnal bird heralds death is present in the image of Santa Muerte. In New York’s altars, this myth is represented by an owl, while an hourglass symbolizes the beginning and the end of a life.”
Other Mexican myths claim the owl is a bad omen and hearing one hooting is as sign that death is nearby. This lines up perfectly with Sunday’s Fear the Walking Dead episode, where the owl WAS ominous and DID indicate death was nearby. It’s no wonder Daniel threw Luis’ coin away... he probably wanted nothing to do with a death cult.
- Skybound Comics: Everything You Need to Know About Fear TWD's Owl