The image you are seeing is a kind of trap that is used to trap wild birds. This trap uses glue to catch the birds as they plunge. People use birds of prey and sounds to entice birds to fly in the sky.
In Vietnam there are many types of traps to catch wild birds. But mostly use nets and glue sticks! Because these 2 options catch many birds at the same time.
In Vietnam people trap small sour birds like worms to big birds. Most of them become food, except some birds become pets.
One thing I have to admit is that Vietnamese people love wild foods, which are foods that are not naturally raised by humans. :(