RT16: Radiotelemetry on territorial birds in remote areas

Sun, Y-H. & Dowell, S.D. 1999. Radiotelemetry on territorial birds in remote areas. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban: 3191-3192. Johannesburg: BirdLife South Africa.

Radiotelemetry has been used as a technique to study wild birds since the early 1960's. Satellite telemetry has been used to study some migratory species but most telemetry work is focused on the ecology and breeding biology of territorial birds. This discussion focused on the particular problems experienced when radiotracking birds in remote areas including problems with trapping, fitting radiotransmitters, radiolocation (signal reflection, interference), constraints on data collection and obtaining a sufficient sample size.

The session began with a short presentation from Sun Yue-Hua on his work on the Chinese Grouse Bonasa sewerzowi at the Lianhuashan Nature Reserve, Gansu province, central China. During his 3-year study, more than 50 birds were radioed. The capture methods used for these birds include mist nets, walk-in traps and noose pull. Grouse were fitted with a radiotransmitter mounted on a necklace collar weighing 3-4% of the bird’s overall weight. Radiotelemetry has the birds marked, enabled nest sites to be found, causes of mortality to be determined and winter flocking and mating behaviour to be studied. The examples of problems encountered with this study set the theme for the remainder of the discussion which was opened out to the assembled participants under above problems.

Most researchers have their own trapping methods for their species. What we discussed at some length was that of catching females on the nest. There is a real danger of abandonment which can be reduced by trapping the female in the last few days of incubation when her urge to incubate is strongest.

As to obtaining radiolocations, we got the solutions that wet weather can interfere with the signal; vegetation may cause reflection, however, it is less of a problem than people realise; physical obstructions like cliff faces are usually the main cause of reflection. When you study wetland birds in wetland habitats (e.g. reedbeds), surface water could cause strong reflection, we did not reach a good solution to solve this problem.

In remote areas, most researchers do radiotracking by carrying the receiver and hand-held antenna and following their radio-equipped animals. Some possible solutions were discussed on this topic, it was suggested to use Yagi antenna for hand tracking. When locating the bird, you should hold antenna in horizontal plane, and keep moving and obtain fixes from multiple locations. You will gain experience of tracking your species.

One problem that had been encountered by several participants was that altitude, air pressure and temperature may affect the accuracy of radio fixes. A solution to this might be to have an altimeter built into the transmitter and to measure altitude, pressure and temperature when radiotracking.

The following points arose from discussion on attachment methods: You should be careful when using harnesses as they may damage the bird’s plumage and skin. Collars and necklaces are suitable for some game birds but risk altering the birds balance, especially in flight. Tail mount is a safe method, but only possible for species with a significant tail (e.g. raptors). Using glue-on pads method, the glue should be strong enough. It is important to use biodegradable material for the transmitter pads so that tag eventually drops off. The suggestion is to try Stabiloplast (works at low temperatures) or Avian Epoxy (strong).

For the sample size, if you can only tag a limited number of birds it is important to determine a suitable time interval between radio locations to establish independence. A suggestion was made that a minimum of two hours between fixes is necessary with a maximum of three radio locations per day. Exact timing will depend on species, habitat and objectives of study. When planning radiotelemetry projects it is important to remember your wastage and account for it when determining your sample size.

The main message to emerge from the discussion was that with any radiotelemetry project it is essential to know your animal before you start. This includes familiarising yourself with the terrain of its environment before you plan the fine details of the project. The key to a successful radiotelemetry project is thorough preparation.