MEXICO CITY — To plot his escape from the most secure prison in Mexico, Joaquín Guzmán Loera, the drug kingpin known as El Chapo, is believed to have relied on countless little birds to whisper information into his ear and help whisk him to freedom.

Now, it appears that at least one of them was an actual bird.

Government officials visiting Mr. Guzmán’s cell after his breakout discovered the body of a small bird sitting in his trash can. The bird, they believe, was used to test the air quality of the tunnel through which Mr. Guzmán vanished — like coal miners who used canaries — according to an official helping to coordinate the manhunt.

Officials are calling the bird “Chapito.”

It was one of many marvels of the kingpin’s escape. The architects of his tunnel gave it lighting, a motorcycle on rails to transport the displaced earth and oxygen tanks. It was built high enough so that Mr. Guzmán, whose nickname El Chapo means “Shorty,” could stand.