Processing a raptor basically means to attach any identification markers and gather the physiologic or biometric data that a bander, scientist or project is interested in. Typical data comprises but is not limited to information such as, species type; weight; age and sex; tarsus; wing chord and tail length; health or physical appearance; location of capture/recovery, etc. In addition to the routine banding programs, special trapping projects are often established to collect specific or unique data such as blood or feather samples for DNA studies, insect parasites hitching a ride on the raptor or for attaching radio or satellite telemetry devices for tracking. One season we attached strips of plastic tape to the deck feather of Red-tailed Hawks, different colors were used as the season progressed, with the intent of determining how long the Red-tailed Hawks would loiter in the Kiptopeke area.
After catching a raptor and removing it from the trap, it must be quickly restrained to prevent injury to itself or the trapper and bander. The raptor is immediately placed in a cylindrical container small enough to constrain its wings and feet, but not so small as to restrict breathing. A simple and effective container is made by attaching two appropriately sized cans end to end, one can with both ends removed, and the other with one end removed. Ventilation holes are cut in the one end to allow unrestricted airflow. Different diameter cans for different species and sex of raptors. Coffee cans for Red-tailed Hawks, Pringles potato chip cans for Sharp-shinned Hawks, to tomato paste cans for American Kestrels. The darkness inside the can helps to calm the raptor and the constraint prevents the raptor from thrashing around and injuring himself or others. With the trapper's hands free, he can reset a trap if necessary, or return to the trapping blind.
Inside the confines of the cozy blind and with the raptor restrained, he can be processed by a banding assistant or the trapper himself. When not being handled, the raptor-in-the-can is layed chest down so as not to impair his breathing.
The raptor-in-the-can is very briefly stood on his head and weighed using a digital scale and then the weight of the can is subtracted from the total to compute the raptor's actual weight.
Typically, the USFWS band is applied before anything else is done with the bird, so that in the unlikely event he should escape, the identifying band has been attached. If this should occur, at least the species type, and possibly age and sex will be recorded. After banding the raptor, the bander can acquire other data. While the raptor is still in the can, the bander opens an aluminum band of the appropriate size in preparation to attaching it to the bird's leg.
The can is roomy enough to reach into and pull out one of the raptor's legs to afix a band. In this manner, the bander can apply the band without injury to the raptor or the bander. After the band has been opened wide enough it is passed over the raptor's tarsus, gently squeezed closed and then locked in place by folding over the locking tab with pliers.
Once the raptor has been banded it can be handled to acquire other data without fear of releasing an unbanded bird. Some measurements can be made with the bird remaining in the can, such as measuring the hallux, the largest of the bird's talons.
Another common biometric measured is the length of a raptor's wing chord. In some species of raptors, for example, Cooper's Hawks and Sharp-shinned Hawks, wing chord length and weight can be used to determine their sex.
Depending on the species of bird, other methods and techniques are available to constrain and calm the bird. Passerine banders use cloth or paper bags. During a period of time when I helped banders catching Saw Whet Owls, they used the cage shown in the image below.
Then, after the hawk has been poked and prodded and all the relevant information collected, he is sent along his way.