A tail-mount transmitter is attached to the underside of one to four tail feathers using glue and braided nylon fishing line. Retention is based on seasonal molting patterns which allow a transmitter to remain attached for a few weeks to as long as 9 or 10 months. This design is most often used on raptors and sometimes used on gulls and terns.

The tail-mount attachment has several advantages. There is no harness around the neck, wings, or body to encumber movement. It is not necessary to recapture the bird to remove the transmitter because it falls off when the tail feather is molted. The trailing whip antenna may also reduce drag during flight when compared to other designs. Body growth of young birds is not a concern because the transmitter is attached to the tail rather than around a growing part of the body.

A disadvantage is the lightweight requirements limit the field life. The possibility of premature feather loss exists which would reduce the time a bird can be monitored.

Series	Weight (grams)	Life (days)	Description
A4500	2.8-4.7	74-468	Smallest sizes, reduced power output for longer life, minimum potting for lowest weight., silver oxide battery. Rectangular shaped, tail attachment with single groove.
A4600	6.0-35.0	65-2035	Medium size, standard power output for normal life, normal potting for durability, lithium battery. Cylindrical shape, tail attachment with two grooves.