Trombicula (otherwise known as chiggers, red bugs, and harvest mites) are a type of mite from the Trombiculidae family. The disease caused by infestation with the larvae is referred to as trombiculiasis, or chigger infestation.
Transmission: Trombicula larvae will attach themselves to the skin of the birds, through a feeding tube produced by the interaction of their saliva and the surrounding host tissue. They feed on partially digested skin cells dissolved by their salivary secretions, and will usually remain attached to them for 1 to 5 days. Chigger larvae are usually found under the wings, around the vent, or on the head around the eyes and on combs and wattles. After the larvae are done feeding on the bird, they'll drop to the ground and molt into their nymphal stage.
Appearance: Chigger larvae are quite small (0.2 mm long), and are red to orange in color. The adult female will lay their eggs in the soil, which hatch in 6 days. The complete life cycle of the chigger mite takes from 2 months to 1 year or longer, depending on the environmental conditions and species. The chigger larvae are most prevalent in grasses, forests, or swamps in late summer and fall.