...using a miniature archival light level recorder
A miniature light level logger (geolocator) for tracking animal movements for long periods has been designed and developed by engineers at the British Antarctic Survey.Because they do not use satellite or radio technology, our loggers can be made much smaller and lighter.
Thousands of these instruments have been used by the British Antarctic Survey (BAS) and collaborators on a number of species. They have mainly been used for bird migration tracking but other long distance movements could be tracked in the same way. They can be used for tracking over long distances in any application where the logger usually has an unobscured view of natural light level at dawn and dusk. The loggers must be retrieved for data download.
Our light level geolocator is a miniature, light weight archival tag recording essential light level information which can be processed to give location latitude and longitude. The devices are small, have low weight and drag, long lasting and cost effective. Although not as accurate as GPS or ARGOS, this method allows a much cheaper and much smaller device to be constructed which records for a far longer time (many years). For seabirds, logging of wet/dry information and sea surface temperature can also be included. The wet/dry recording has been developed to measure the activity of the birds, and the temperature information, when correlated with satellite data, can be used to improve the location fix. The opportunity to put these loggers on smaller birds for which movement data is required is great and we welcome collaborators.
The loggers work worldwide wherever there is dawn and dusk, and have been used so far on a number of species including geese, albatross, penguins, shearwaters, gannets, skuas, fulmars, ducks, shags and seals. Being so small, they can be attached to leg rings of larger seabirds, thus avoiding problems associated with platform gluing and harnesses. Accuracy is in the region of +/-150km and uncertainty is caused mainly by shading (including cloud and foliage), interference (non direct sun and artificial light), and for latitude, proximity to equinox and the equator.
Now that we are making devices under 1.5g, use of them to track songbird species is now beginning to be explored. A leg-loop harness, similar to the Rappole-Tipton method has been favoured so far. For back mounting with a harness, we have developed devices with the light sensor on a stalk to clear the plumage of the bird. We have now released the Mk12-S device; it is our smallest logger suitable for back mounting with a weight of 0.9g and a life to record for more than a year. The tag will include loops and tube to attach the harness material and so reduce the weight of the attachment needed; an improvement on our Mk10-S.
