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Capture and Marking:Capture of sandhill cranes for attachment of satellite transmitters is accomplished using large nets propelled by rockets. We set these nets at active loafing areas, usually a pasture or grassland, which cranes frequent after their morning or afternoon feeding bouts. Once the net is set and camouflaged, several decoys (taxidermy mounts) are placed around and in front of the net to "coax" the cranes into the "throw" of the net. The nets are fired using remote radio-controlled detonators, allowing us to remain concealed at a distance from the net. When the opportunity arose, sometimes after waiting concealed for several hours, we fired the net. Upon a successful net firing, each crane captured is banded with a Bird Banding Lab aluminum leg-band. Of cranes captured under the net, one is usually selected to receive the satellite transmitter. Structural data is recorded and a blood sample is taken from this crane so that the subspecies can be determined at a later date. The 30 gram (approximately 1 ounce) transmitter, which is mounted on a plastic leg band, is placed above the knee joint on the crane's leg. After all data are recorded and the transmitter attached, each transmitter-equipped crane is released with the other trapped cranes to rejoin flocks and continue their northward migration. All capture and marking procedures were approved by the Northern Prairie Wildlife Research Center Animal Care and Use Committee and conformed to recommendations of the American Ornithologists' Union (1997). |
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