Color-marking of cranes
Throughout a whole year cranes are present as breeding, migrating or wintering birds in most European countries. Detailed biological knowledge about the different phases of life is poor or almost missing. Some of these information gaps can be filled with information by a European-wide project which include color-marking of cranes and the use of different types of transmitters.
For individual differentiation the cranes have to be marked. In Europe this happens consistent with colored plastic rings (agreements of the European Crane Working Group), radio transmitters (frequency range between 148 and 149 Mhz) and different types of GSP-GSM transmitters. Seven colors are available: white, yellow, red, blue, green, black and brown. The color combination on the left leg is coding for the country, while the code on the right is coding different individuals.
With the help of sightings and records from colormarked or tagged birds important information about migration routes, winter quarters, distribution, pair bound, breeding and territorial behavior and survival rates is gathered and can be used for conservation activities.
The field work
Capturing cranes is teamwork. At least four persons are in the team. They are all in contact with each other with radio devices. All people have to make sure, that they are not visible for the cranes.
The team is usually divided into catchers (usually two) and observers of the crane family. While the catchers are sneaking off to the cranes using available vegetation cover, the rest of the team observes the crane family with one or two juveniles. If the catchers are in a good position, they coordinate the catching event with the observers. The observers then fix the position of the juveniles and catching attempt can be started.
One, two, three! The catchers reduce the distance to the cranes. When the adult cranes see the catchers, they are usually flushing away. Using snarling sounds the adult cranes try to communicate with their offspring and are advising them how to react.
Sometimes the still flightless juveniles are running away from the catchers. Mostly they were overtaken. Usually the young cranes try to hide up in the vegetation and are no longer visible for the catchers. Now the observers are directing the catchers to the last position of the juveniles. Often the catchers can find the juvenile cranes deeply covered in the vegetation. The adult cranes are flying over the catching place and landing in some distance. From here they are watching the event.
For sedation the cranes are getting a black cap on their head. After the marking with rings and tags the cranes are released and quite soon re-integrated in their crane family.
The ringing system
The ringing project is a result of agreements within the European Crane Working Group during international crane meetings in Tallinn/Estonia (1989), Orellana la Vieja/Spain (1994) and Stralsund/Germany (1996).
Since the mid-1980ies cranes were marked with red legrings, wearing a white alphanumeric code. From 1990 onwards, cranes are marked with specific color combinations at the tibia, were a three-ring code on left leg is coding the country and another three-ring code on right leg is coding the individual. In addition to these plastic rings, the birds are banded with a metal ring of the responsible bird ringing Centre.
The best time for crane banding is, if the juveniles are less than ten weeks old and before they are ready to fly. As an exception, sometimes also adult cranes can be caught during their wing moult. Every three to four years they are moulting their wing feathers and in this period they are flightless, too.
The 2 cm high rings consist of two halves, which are quickly pressed together and attached on both legs always on the tibia bone. On the left leg the country code is attached. For Germany these are combinations of at least two blue rings or three brown rings. On the right leg a three-color code is used to allow for an individual identification, but the same color is never used on top of each other.
With this "ID card" on both legs, the crane is unique and recognizable during migration throughout Europe by ring readers. The observations of color-marked cranes in Europe can be reported via the specially created online database iCORA.
The marking is often financed by sponsorships. With a unique donation, you become a sponsor of a specific crane and can follow his life-history, but you also help to support crane research.