Capture Methods

Table 9. Recommended Capture Methods for Waterfowl and their Allies.

Species Group	Capture Method
Sandhill Crane	Cannon/Rocket Nets when flying, usually decoyed in.
Swans	Cannon/Rocket Nets when flying, usually decoyed in.
Geese	Drive Traps when moulding and for flightless young.

(1) Cannon Net Trapping /Rocket Net Trapping

• Recoilless rocket cannons with attached nets have been used successfully at Malheur National Wildlife Refuge to capture geese, Sandhill Cranes and other species (McLaury pers. comm.).
• This method requires setting up traps well in advance and baiting birds to get them used to it. This may take several days. Once birds have experienced this method, whether they were caught or escaped, they become very wary, so a site can be used effectively only once for species other than dabblers.
• The body of the rocket cannon is of high strength tubular construction. Welded at the rear of the cannon body is a stabilizer rod which has a 3/16 inch chain attached. This chain is for attaching net leads (Dill, 1967).
• Although the cannon requires no launching tube or rail, a launching rail improves the vertical angle of deployment of the rockets and prevents the rockets from tipping over (McLaury pers. comm.).
• Two types of nets were used with the rocket cannons at Malheur, the entanglement net and the skirt net. It was found that the skirted net worked best for capturing all species. The birds were easier to handle and physical stress while under the net was reduced (McLaury pers. comm.). For more information, see Schemnitz (1980), (especially pages 77-78 of chapter 6 - Capturing and Marking Wild Animals, and chapter 14 - Estimating the numbers of wildlife populations, pages 221-246).

(2) Goose Wing Trap / Key Hole / Drive Traps

• This trapping method is used when the goal is to capture a few to several hundred geese with little investment in time and money.
• Trapping is conducted early to mid June (although this depends on where trapping is in province) when the goslings are of considerable size, feathered, yet still flightless. In hot weather, it is important that trapping be done in the early morning to prevent heat stress to the geese.
• The trap consists of any kind of wire pen (in Stanley Park, conveniently located tennis courts are used) and fence wings extending from near the water's edge to the cage entrance (e.g. snow fencing; linked, 4 x 8 foot sections of aluminium-framed wire fencing). The size of the pen depends on the number of birds being captured: small number of geese (<25) should have a pen space at least twice the size required by a group of crowded birds; for larger numbers requiring more processing time, birds should have at least five times the space they require when crowded. Water must be provided in the pen.
• At least two boats are needed to move the geese back onto land into the wings of the trap Exact number of boats will depend on the size of the trap and the number of geese, (one experienced trapper with a canoe can drive and capture up to two dozen geese in places where they are used to people, such as the lower mainland or the Okanagan).
• Ground personal are usually needed to herd the geese down the wings of the trap into the capture pen.
• Once the geese are inside the capture pen the banders may enter the pen and begin banding. The geese should only be approached from one side of the trap to avoid trampling. If large numbers are caught, a subsection should be made in the pen into which a few birds at a time are corralled for processing.

Data analysis

The project biologist should be familiar with the different methods of data analysis for mark-recapture inventories before data collection begins. Different assumptions and requirements of the various models will have great bearing on sample design, effort and overall approach.

Section 3.5.7 is a cursory discussion of mark-recapture models. This is included to provide biologists with an overview; however, a greater depth of knowledge will be required to actually carry out a mark-recapture inventory. Prior to commencing, it will be necessary to consult Species Inventory Fundamentals No. 1 as this manual provides descriptions of many techniques which are generic to species inventory. In addition, the following is a short list of some useful texts and articles. For complete citations see References.

• White et al. 1982. In some opinions, this is by far the most readable reference on mark-recapture that is available. Available at: http://www.cnr.colostate.edu/~gwhite/software.html
• Buckland et al. 1993. Good text for distance and transect sampling.
• Krebs 1989, (also 1998, 2^nd Edition). Good all round discussion of study design, but Chapter 2, Estimating abundance: Mark-and-Recapture techniques, is especially appropriate).
• Pollock et al. 1990. A good discussion of the Jolly-Seber model.
• White and Garrot 1990. A good discussion of study design for radio-telemetry estimation studies.
• White 1996. A good discussion of mark-resight estimation procedure.
• Schemnitz 1980. Wildlife management techniques manual (especially chapter 14 - Estimating the numbers of wildlife populations, pages 221-246).