Geolocators

Light-level and multi-sensor geolocation

Satellite-based Global Positioning Systems (GPS) for tracking migratory birds year-round are still too heavy for most passerines. Therefore, more lightweight alternatives have been developed: light-level and multi-sensor geolocators. Light-level geolocators measure the intensity of ambient light and store this data together with a timestamp in the device’s internal memory. Multi-sensor geolocators, in addition to measuring ambient light, harbour sensors for recording atmospheric pressure, ambient temperature, bird’s acceleration, and intensity of the magnetic field. Once retrieved, these data allow location determination of the bird throughout the annual cycle as well as additional information on the individual’s behavioural patterns, flight performance, and more.

Significance

Before the introduction of geolocators, the knowledge about whereabouts of our songbirds outside the breeding season was very fragmentary. Thanks to geolocators, it is now possible to record the course of migration of individual songbirds in space and time year-round, including their stopover locations, migration routes, non-breeding sites, flight behaviour and altitudes, daily activity patterns, etc.

Aims

Our geolocator-based studies aim at:

recording present day natural history information of migration patterns in various species and populations for future record
understanding environmental and genetic influences on the temporal and spatial patterns of individual migration behaviour
measuring year-round energy expenditure in long- and short-distance migrants
linking individual migration patterns and performance with past and future reproductive success (i.e., carry-over effects)
evaluating migratory connectivity between breeding and non-breeding areas and its consequences for population dynamics
assessing route choice relative to migration barriers
investigating migration behaviour in the face of anthropogenic change
developing and improving analytical tools for geolocator-based data

Approach

Any geolocator-based study is inherently composed of hardware that is deployed on birds to track their movement, and of software that is subsequently used to analyse the collected data.

Hardware

The Swiss Ornithological Institute together with the Bern University of Applied Sciences developed and is producing three types of geolocators:

A) a featherweight light-level geolocator for exclusive recording of positioning data (model: GDL2, weight: 0.6 g)

B) a light-level geolocator with a remote data download option (model: µTag, weight: 1.5 g)

C) a multi-sensor geolocator equipped with additional sensors for measuring ambient temperature, atmospheric pressure, bird’s activity (acceleration), and intensity of the magnetic field (model: GDL-PAM, weight: 1.5 g)

A) a featherweight light-level geolocator for exclusive recording of positioning data (model: GDL2, weight: 0.6 g)

B) a light-level geolocator with a remote data download option (model: µTag, weight: 1.5 g)

Software

Partners

Bern University of Applied Sciences
Simeon Lisovski, Alfred Wegener Institute, Potsdam, Germany
Kiran Dhanjal-Adams, Royal Botanic gardens, Kew, Richmond, United Kingdom
Silke Bauer, Swiss Federal Institute for Forest, Snow and Landscape Research WSL
Steffen Hahn