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Great reed warbler migration

During recent years, new technology has made it possible to obtain hitherto unknown information about animal migration. For example, satellite tracking of individual birds during repeated migratory journeys has provided new and much detailed knowledge about spring-autumn differences in bird migration and about site fidelity. However, for small birds, like passerines, the use of satellite technology has been impossible – simply because they are too small to be fitted with a transmitter.

The development of geo locators, or light loggers, has changed this, though, and now it is possible to track even as small birds as great reed warblers (Acrocephalus arundinaceu), weighing about 35 grams. In this project we hope to be able to map great reed warbler winter-and spring migration and also investigate sex differences in migratory strategies by using light logger technology.

Logging light data

Willow warbler
Photo: William Velmala
Light loggers measure and store light intensity and time, and when retrieved the data can be used to calculate the animal’s latitude and longitude using a process known as light-based geolocation. Here, a great reed warbler fitted with a light logger weighing 2,5 grams.

Different arrival time

Warbler with logger
Photo: William Velmala

In 2008 we fitted 25 individuals with loggers and recovered 8, which is what could be expected from previous returning rates to the lakes without loggers. This data is yet to be analysed but look very promising. In 2010 we used an even smaller logger (1.8 grams) and could hence include females in the project. This is very exciting due to the prominent differences between sexes in arrival time at the breeding grounds. Here, one of the first returning great reed warblers is released from its light logger.

Page Manager:

Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden