The University of Amsterdam Bird Tracking System (UvA-BiTS) was developed by Edwin Baaij of the Technology Center and Willem Bouten and Judy Shamoun of the Institute for Biodiversity and Ecosystem Dynamics, all at the University of Amsterdam. It has been designed to answer the needs of people with diverse research aims and interested in tracking birds. The same system can be used to monitor fine scale foraging movements and behaviour every few seconds as well as migratory movements across thousands of kilometers.  UvA-BiTS is a flexible and modular system providing users with control of their tracking studies, even while tags are on free ranging birds.

Key features of the system include a solar powered, lightweight GPS tag with rechargeable batteries, multiple onboard sensors including a tri-axial accelerometer, two way data-communication to a ground station network, automated data processing and visualization.  The combination of programmability and two-way data communication is a unique feature that enables the user to tailor the measurement scheme to the needs of the research while the tag is still on the bird.

GPS device

The GPS device

The GPS device consists of the following (electronic) sub-systems:

  • GPS engine
  • Microcontroller
  • 4 MB flash memory
  • Temperature sensor
  • Tri-axis accelerometer
  • Barometric pressure sensor
  • Solar panel
  • Lithium polymer battery
  • Battery charging circuit
  • Zigbee two-way radio transceiver
  • Weight: 12 – 19 g
  • Battery capacity: 65 mAh or 240 mAh

The GPS device is a data logger that can be programmed remotely. Using a Zigbee two-way transceiver unit, data can be remotely downloaded from the logger and new measurement settings can be uploaded. The diverse measurement scheme features make it possible for the user to create a scheme that takes high resolution measurements at certain times, locations, or under other special conditions and lower resolution measurements at other times. The microcontroller unit (MCU) is the “computer” of the GPS device, with internal software (firmware), which controls the functionality of the GPS device, including managing the solar cells, measurements, data storage and connection to the network. The 4Mb flash memory is capable of storing 60,000 GPS fixes. It is used as a circular memory, so once data is downloaded, memory is free to be used again.

Large GPS device for the Griffon Vulture

The tri-axis accelerometer has been programmed to take 20 tri-axis measurements per second. The user can adjust the duration of the accelerometer segment. The data can be used to analyze the behavior of the bird. Flapping, soaring, gliding, sitting, floating, even the wing-beat frequency can be calculated. The pressure sensor has a resolution of 1 Pascal. The temperature sensor measures the temperature inside the device. The total weight of the device ranges from 12 to 19 grams and depends on the chosen capacity of the battery and the amount of applied epoxy to strengthen the device. The lightweight version GPS device has been expanded for use on large species like vultures and storks. For this type, the weight can vary from 40 to 50 grams. Again it depends on the chosen battery capacity (560mAh or 900mAh) and the amount of epoxy. This type has 8 solar cells.

In addition, a new GPS mini-tracker charged by 2 solar cells and weighing as little as 5.8 grams has recently been developed. The accelerometer of the new device has been redesigned to enable higher resolution acceleration sampling (20 or 50 samples per second), and the memory of the device is eight times larger than the original loggers. To read more about the new device, click here.

Data transmission and coordination

Installation of a Relay Station

The UvA-BiTS field unit consists of one base-station, one or more relay stations and GPS devices on birds. The base-station is the system’s coordinator and is connected to a netbook.  The computer runs the Birdtracking program to download and store the data in files, and is also the user’s graphical interface to design new measurement schemes for upload.  Data is transmitted to the UvA-BiTS ground station network with no additional cost for data communication which is crucial for a system that can collect massive amounts of data. The device can only communicate inside the reception area and when in communication mode. Outside this area, it logs all data until the next time in connects to the network. The relay stations are important signal repeaters and together with the base-station define the area of reception. A reception area of hundreds of square kilometers is feasible. The relay-stations are weather proof and battery powered and can operate for 100 days on 1 battery-pack.

Base station with netbook

The ground station (base and relay) creates a wireless network the GPS devices can connect to. Once communication is established between the base-station and the GPS device, the base station takes over, first sending new settings if provided by the user, then downloading data. When all tasks are complete, the base station ends communication with this device and the device can continue logging data. The base station can be run on a small to medium solar-energy system and the netbook can be connected to the internet by a GSM USB dongle, a 3G router or other dedicated way.

Measurement schemes

Base station software

A basic measurement scheme runs 3 tasks:  GPS measurements, accelerometer measurements and communication. Each task is defined by a repeat interval in seconds. The interval can vary from 3 to 60000 seconds. Mostly GPS ranges from 3 (high resolution) to 7,200 seconds. Communication ranges mostly from 300 to 1800 seconds.  Accelerometer measurements, generally used to identify behaviour, can be taken independently or directly following a GPS fix, to provide a geo-location for the accelerometer measurements.  To create more flexibility, each task can be programmed separately for two different time blocks per day and two different geographic areas.   One additional feature is the Energy Surplus feature. When enabled, the GPS measurement interval is temporarily lowered to a user specified interval as long as the battery is full.

Virtual Lab

The Virtual Lab is an eScience research infrastructure for handling the massive amounts of data that can be obtained with the UvA-BiTS.
Through the internet and the use of Dropbox, the stored raw GPS data on the netbook is automatically transferred to the Virtual Lab, postprocessed and stored it in a centralized spatial PostGreSQL database. The user can monitor the performance of the loggers on the basis of summary statistics and can generate KML files of their own GPS data for visualization in Google Earth. Users can query their own and public data in the database, by using a graphical query builder or a Structured Query Language (SQL).

New GPS mini-tracker facilitates research into movement of smaller animals

In response to the needs of researchers studying smaller animals, a new GPS mini-tracker weighing as little as 5.8 grams has been developed. Like the older tracker, the new device is capable of measuring GPS location, acceleration and internal temperature of the device, but now within a smaller and lighter package. Read More

Availability of GPS-trackers for scientific research

We do not make tags for commercial purposes but only for collaborative research (shared property of data and joint publications). We are interested in cooperation if the scientific questions are interesting. In general this means:
  1. a challenging scientific question and experts on the species involved
  2. large enough sample size
  3. tracking is combined with field observations
  4. determination to make the project work and to publish about the results.
Our research focuses on flight dynamics in relation to weather and landscape properties during migration or local (foraging) flights.

Contact persons:

Willem Bouten, IBED-UvA, Edwin Baaij, TC-UvA,



UvA Technologie centrum