 |
Capture & Tracking Techniques |
 |
|
||
|
||
|
||
|
Based upon the annual mid-winter waterfowl survey in North Carolina, the highest concentrations of wigeon are located in coastal areas in Hyde, Dare, Pamlico, and Beaufort counties. All wigeon were captured on private lands adjacent to Lake Mattamuskeet and on Mattamuskeet NWR utilizing rocket nets. Adult hens were chosen to be fitted with transmitters because they are likely to return to where they were hatched or raised broods in previous years. Adult hens were identified by molt and wear patterns on wing feathers. All other wigeon and non-target ducks were leg-banded and released on site.
The satellite transmitters (called PTT's or Platform Transmitter Terminals) are manufactured by Microwave Telemetry, Inc. and weigh 18g. The weight of the transmitter is critical as the overall weight of the transmitter/harness package should not exceed approximately 3-4% of the weight of the bird. Therefore, only hens weighing >775g were chosen. The battery within the transmitter is charged by a solar-cell on the top of transmitter which allows for operation up to 3 years. Until very recently, technology did not exist that allowed for such a lightweight package with an extended battery life. The transmitter rests on the back of the bird and is attached with a Teflon ribbon harness. After wigeon were fitted with transmitters, they were kept in holding pens up to 2 days to ensure each bird adapted well to the transmitter package before being released at the capture site.
Transmitters may be programmed an infinite number of ways, depending upon study objectives. In 2006 and 2007, the solar satellite transmitters were programmed to send a signal every 65 seconds for ten hours during a 72-hour period. This routine ensured the solar cell was able to sufficiently recharge the battery and allow us to track the broad-scale movements of wigeon through spring migration, breeding, and the following fall migration. In 2008, we adjusted the duty cycle to send a signal every 65 seconds for ten hours during a 36-hour period.
Signals are picked up by an ARGOS tracking system receiver attached to several NOAA polar-orbiting weather satellites. SERVICE ARGOS is a cooperative venture under the joint management of France's Center of National Space Studies, and the United States of America's National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA). The purpose of ARGOS is to allow researchers to remotely collect environmental data on a wide range of subjects, including: meteorology, oceanography, and animal ecology. The data is then relayed down to earth where locations are determined by ARGOS and then sent directly to Commission waterfowl biologists.