Tracking Migratory Birds Using GPS

AKIRA FUKUDA

Start of GPS-logger-for birds development team

Our team consisting of communications researchers, wild animals researchers and electronic engineers has been developing ¡Èlong-term automatic positional information collecting system for migratory birds using GPS.¡É We have successfully observed round-trip food collecting journey paths of Galapagos albatross from their nest in Espaniora Island to Peruvian coast using a prototype system in June 2001.

This project was triggered in the conversations between the author and Dr. Makio Suzuki who is a Lecturer at Department of Oceanography at Tokai University studying wild animals. Dr. Suzuki told me that satellite tracking system (Argos System) were mainly used to observe paths of migratory birds but there were problems that the cost was expensive and the accuracy was not good enough. Actually, real time positional information is not what we always would like to get. We really would like to know the paths of migration. This is the reason why we decided build a totally passive system consisting of a GPS receiver and a storage device.

When we asked for comments to Professor Hiroshi Higuchi of Graduate School of Agriculture and Life Sciences, University of Tokyo, we had positive support from him as well as valuable comments about requirements and choices of birds which are appropriate to use in experiments.

Following such comments, we asked for technical cooperation to Mr. Katsuji Miura of Koden Production Corporation. The basis of the development team was formed then. The development team was completed three years ago when Ms. Emiko Morishita, a researcher in Professor Higuchi¡Çs Laboratory and Mr. Hisaki Maeda of Koden Production Corporation and Mr. Hitoshi Takamizawa of Trix Corporation joined.

The development team held study meetings frequently in which comments from various disciplines such as migratory birds behaviors, GPS equipment performance, software and communication systems were discussed. After prototype fabrication and revising it, the system was completed in the spring of 2001.

Observation principle and equipment configuration

The device in the system to be attached to a bird consists of a GPS receiver module, GPS antenna, a timer, a storage device, a battery and a cover. The receiver collects positional information according to the preset schedule. The trial system uses a commercial lithium battery as a power source weighing 100 g. It has 6 kB memory capacity and is able to store latitude and longitude with an accuracy of seconds. The maximum observation times is about 500 which is limited by the battery¡Çs capacity. To save battery energy, the system completes one cycle of observation if the positional information is obtained within 50 seconds. Otherwise, it extends the observation time up to another 30 seconds.

In the next version which is to be completed at the end of year 2001, the weight will be 80 g. The observation accuracy will be increased down to 1/1000 of a minute. Both types of prototype bear up to 3 atm of air and water pressure. Figure 1 shows a picture of a prototype device. In this system, the position data are collected after the equipment is retrieved. This feature gives advantages of light weight, longer battery life and lower cost. On the other hand, it is not good for some kinds of birds which are hard to catch again to retrieve equipment. However, if retrieval time exceeds some point, this system will achieve paths investigation with 10 to 100 times higher accuracy and a cost of 1/50 to 1/500.

Tracking Galapagos albatross

The current prototype is relatively heavy and requires recapturing of birds. Therefore, the applicable birds are limited. Thus we decided to collaborate with Associate Professor Dave Anderson of Wake Forest University, N. C, who is an expert of Galapagos albatross studies.

The two onsite experiments in the last two years were conducted by the research team of Associate Professor Anderson. In the first year, brief preliminary experiments were conducted. In the second year, Professor Higuchi and the author visited Professor Anderson to explain how to use the observation system directly after fine-tuning the system repeatedly. As a result, one of the devices has successfully observed positioning data at a rate of 6 times a day (see Fig. 2). From this result, even the author, an amateur in this field was able to imagine vividly how albatross travels 1600 km one way without sleeping at all at a speed of 520 km/day in order to get foods for their children. I was also able to imagine that they kept eating for 10 days, and one day leave decisively for their home in a isolated island in the ocean. I realized that it was not right call albatross unwise.

Future prospect

In the next breeding season, I plan to bring the new prototype myself to observe positional information of a few of the birds with a shorter periods collaborating with Associate Professor Anderson. I would like to give a next prototype a minimum transmission capability. To describe more in detail, I would like to set a receiver at the end of the investigation. When the GPS finds that the bird is close to the end point, stored data in the memory should be transmitted to the receiver using the remaining energy in the battery.

The author and his coworkers are planning to develop some variations of this system for different applications. For example, the following types are being discussed: (1) lighter and smaller type with less pressure resistance, (2) bigger type allowing a larger battery for mammals, (3) a type with high pressure proof for such birds as penguins, (4) type (3) with data transmission capability, (5) a type that drops off at an appropriate moment and transmits beacon signals, (6) high pressure type with off-line DGPS system, and so forth.

This system is effective not only for tracking wild animals but also natural environment investigation such as ocean currents, floating ices and many others. There should be applications in technological and social studies such as moving paths of trains. We are looking forward to receiving stunning proposals from the readers of this magazine.