TECHNIQUES TO CAPTURE SEADUCKS IN THE
CHESAPEAKE BAY AND RESTIGOUCHE RIVER
Surf scoters and black scoters were instrumented with PTT100 satellite transmitters (Microwave Telemetry, Inc., Columbia, MD) in late winter. This activity took place on both Chesapeake Bay in Maryland, and the Restigouche River in New Brunswick, where satellite telemetry is providing new information about these important areas. The data collected will be beneficial in protecting critical breeding and molting habitat of scoters and improving future management of their populations. Satellite telemetry tracking requires that scoters be captured alive. Several capture techniques successfully used in waterfowl research are described. Two of these techniques have been successful on this project.
Mist Nets: Mist nets were specially designed to be used in deep waters and be free floating. Many obstacles had to be resolved for the nets to withstand wave action, tides, boat traffic, and lack of visibility, yet work in an open water environment. Initially, several prototypes were tested, and after various modifications a design was adopted. We now use a design that utilizes fisherman’s “bullet” foam floats cut in half and clamped around PVC tubing. Pinned to the float poles are PVC weight poles (1.82m), which have a small cinder block attached at one end. These weights act as a counter balance and can be used in fairly shallow water. The cinder block weight is adequate to submerge the floats so they are not visible above the water surface. The PVC net poles are attached to the float poles and painted flat black to reduce their visibility. The mist nets have a mesh size of 121 mm, measure 12 m by 2.6 m, and have two shelves. Mist nets are set vertically over water with the entire system secured to the bottom using 16 m long ropes and Danforth anchors. Decoys surround the nets in several patterns and many ducks flew in to the decoys. Once set, nets are continually monitored. However, in spite of extensive efforts, no ducks were captured with mist nets during the winter of 2000-01 and 2001-02.
Net Gun: A capture net gun (Coda Enterprises, Inc., Mesa, Arizona) was obtained and numerous techniques were tested with deployment of the net. A small styrofoam float is attached to the net with a 15 meter nylon string so it could be retrieved after deployment. It is obviously important to shoot the net on water with depths less than the retrieval line length. Although the net gun worked well, it is dependent on calm seas to attain proper speed for capture and to safely operate the boat. This technique is very labor intensive, often 5-10 shots are necessary for each duck captured. Also, nets are occasionally lost, which adds to the cost of this technique. In March 2001, the first scoter (a male surf scoter) was captured from a fast moving boat from approximately 10 m. A total of 15 surf scoters have been captured using the net gun in Chesapeake Bay during 2001-02.
Night-lighting: Night-lighting was tried, utilizing long-handled nets and slow-moving boats. Flood lights were used, either hand-held, or mounted on the bow of each boat. These lights were powered by a 12-volt battery, or generator. In the Chesapeake Bay no birds were captured. However, 14 black scoters (both males and females) were captured on the Restigouche River in New Brunswick. The night-lighting technique worked most successfully when water conditions were calm and ducks were actively feeding or courting. Cloudy, foggy, or rainy conditions are optimal. Also, it was important to maintain a constant speed, minimizing changes in motor sound volume. A total of 17 scoters (3 surf and 14 black) have been captured with the night-lighting technique.
Captured ducks are held in holding crates with bedding
material to keep them dry and warm.
All captured scoters are banded with USGS bands.
It would be beneficial to band ducks immediately after
capture, so time of capture would be known for each duck and also if
ducks were captured together. On one occasion, two female surf
scoters were captured together in one shot, and once a male and
female black scoter in courtship display were captured with a dip
net while night-lighting
Alison, R. M. 1975.Capturing and marking oldsquaws.
Briggs, R. L. 1977.Mist netting waterfowl. N. Amer.
Dau, C. P. 1976.Capturing and marking spectacled
eiders in Alaska. Bird-Banding 47:273.