BGDL-II: a GPS data logger for birds

We have developed a new GPS data logger consisting of a receiver, timer, memory, and battery. It is principally designed for long period tracking of migratory birds. It can fix 600 positions with one small lithium battery. We can set an arbitrary measuring schedule prior to each experiment. We can, for example, track a bird over six months, fixing positions three times a day. The whole unit weighs 67 g including battery and casing. The casing is pressure-resistant up to 3 bars. The main advantages compared to tracking methods based on the ARGOS system are: 1) several times cheaper equipment, 2) no charge for the use of satellite links, 3) the errors in the position data obtained are more than 10 times smaller, 4) the schedule setting has greater flexibility, and 5) the fixing has a lesser failure rate. However these advantages are realized at the cost of real time delivery of position data as users must re-capture the birds to obtain the stored data. In this paper, we explain the configuration of equipment, principles of operation, and the performance. We also discuss some results of albatross tracking. In the experiment the failure rate in the fixing of the albatross positions averaged 20%.