Marking is similar to banding, in that its purpose is to identify groups of birds, or even individual birds, for tracking purposes. Marking is normally done by putting a harmless dye on the bird´s breast. This can either be done with a squirt gun or by putting the dye near the nest, so the bird rubs itself on it.
Marking is strictly controlled by the Bird Banding Laboratory, so be sure that no two investigators are using the same marking scheme at the same time.
Birding Glossary