M-Series Geolocators

  • M-Series Geolocators

    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, but is now under license to Biotrack.

    Geolocators 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 Geolocation/TDR 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 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, these geolocators can be attached to leg rings of larger seabirds, thus avoiding problems associated with platform gluing and harnesses. Geolocator 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.


  • Aquatic geolocators
    For species associated with water

    Terrestrial geolocators
    For species that do not go in water

    MK5... family (0.75g – 1.2g)
    Legmount for waders & shallow divers


    Expected life 1 - 3 years (model dependent)

    MK6... family (0.39-1.0 g)
    Small bird backpacks

    Small bird backpacks

    Expected life 10 - 24 months (model dependent)

    MK3... family (2.5 g) MK4... family (1.5-2.0 g)
    Deep-diving and larger waterbirds

    Deep-diving and larger  waterbirds

    Expected life 2 - 5 years (model dependent)

    MK5... family & MK7... family (0.75g – 2.0g)
    Larger more rugged tags

    MK5/MK7 family

    Expected life 12 - 24 months (model dependent)

    Options for Marine Geolocators
    • Wet/dry
    • Temperature
    Options for Terrestrial Geolocators
  • Geolocator stalks are measured from the point at which they emerge from the tag, to the centre of the light sensor.

    The stalk extends approximately 4 mm beyond the light sensor for encapsulation. This should be taken into account when considering the effects of drag.

    The tolerance on stalk length is ± 1.5mm.

    Geolocator stalks

    More information on stalks

  • Geolocator tubes and loops
  • Publications using the M-series Geolocators


    Integrating Information from Geolocators, Weather Radar, and Citizen Science to Uncover a Key Stopover Area of an Aerial Insectivore
    Andrew J. Laughlin, Caz M. Taylor, David W. Bradley, Dayna Leclair, Robert C. Clark, Russell D. Dawson, Peter O. Dunn, Andrew Horn, Marty Leonard, Daniel R. Sheldon, Dave Shutler, Linda A. Whittingham, David W. Winkler and D. Ryan Norris
    The Auk 130(2):230-239. 2013 doi:

    Effects of geolocators on reproductive performance and annual return rates of a migratory songbird
    Jesús Gómez, Chantel I. Michelson, David W. Bradley, D. Ryan Norris, Lisha L. Berzins, Russell D. Dawson and Robert G. Clark
    Journal of Onithology 155: 37- 44 (2014) doi: 10.1007/s10336-013-0984-x

    Trans-Gulf of Mexico loop migration of tree swallows revealed by solar geolocation
    David W. Bradley, Robert G. Clark, Peter O. Dunn, Andrew J. Laughlin, Caz M. Taylor, Carol M. Vleck, Linda A. Whittingham, David W. Winkler and D. Ryan Norris
    Current Zoology 609(5):653-659 (2014) doi: 10.1093/czoolo/60.5.653

    Connectivity of wood thrush breeding, wintering, and migration sites based on range-wide tracking
    Calandra Q. Stanley, Emily A. McKinnon, Kevin C. Fraser, Maggie P. Macpherson, Garth Casbourn, Lyle Friesen, Peter P. Marra, Colin Studds, T. Brandt Ryder, Nora E. Diggs and Bridget J. M. Stutchbury
    Conservation Biology, 29: 164–174. (2015) doi:10.1111/cobi.12352

    Geolocators on Golden-winged Warblers do not affect migratory ecology
    Sean M. Peterson, Henry M. Streby, Gunnar R. Kramer, Justin A. Lehman, David A. Buehler, and
    David E. Andersen
    The Condor 117(2):256-261. 2015 doi:

    Geolocator reveals migratory and winter movements of a Prothonotary Warbler
    Jared D. Wolfe and Erik I. Johnson
    J. Field Ornithol., 86: 238–243. (2015) doi:10.1111/jofo.12107

    Minimizing marker mass and handling time when attaching radio-transmitters and geolocators to small songbirds
    Henry M. Streby, Tara L. McAllister, Sean M. Peterson, Gunnar R. Kramer, Justin A. Lehman, and David E. Andersen (2015)
    The Condor 117(2):249-255. 2015 doi: 10.1650/CONDOR-14-182.1

    A Trans-Hemispheric Migratory Songbird Does Not Advance Spring Schedules or Increase Migration Rate in Response to Record-SettingTemperatures at Breeding Sites.
    Fraser KC, Silverio C, Kramer P, Mickle N, Aeppli R, etal. (2013)
    PLoS ONE 8(5): e64587. doi:10.1371/journal.pone.0064587

    Tracking from the Tropics Reveals Behaviour of Juvenile Songbirds on Their First Spring Migration.
    McKinnon EA, Fraser KC, Stanley CQ, Stutchbury BJM (2014)
    PLoS ONE 9(8): e105605. doi:10.1371/journal.pone.0105605

    Hybrid songbirds employ intermediate routes in a migratory divide
    Delmore, KE and Irwin, DE  (2014)
    Ecology letters, 17(10), 1211-1218

    Migratory movements of rhinoceros auklets in the northwestern Pacific: connecting seasonal productivities
    Takahashi, Akinori, Motohiro Ito, Yuuya Suzuki, Yutaka Watanuki, Jean-Baptiste Thiebot, Takashi Yamamoto, Takahiro Iida, Phil Trathan, Yasuaki Niizuma, and Tomohiro Kuwae (2015)
    Marine Ecology Progress Series, 525, 229-243

    Light-level geolocation reveals wintering distribution, migration routes, and primary stopover locations of an endangered long-distance migratory songbird
    Nathan W. Cooper, Michael T. Hallworth and Peter P. Marra
    Journal of Avian Biology 48(2): 209-219 DOI: 10.1111/jav.01096

    Migratory pathways, stopover zones and wintering destinations of Western European Nightjars Caprimulgus europaeus
    Ruben Evens, Greg J. Conway, Ian G. Henderson, Brian Creswell, Frédéric Jiguet, Caroline Moussy, Didier Sénécal, Nele Witters, Natalie Beenaerts and Tom Artois
    Ibis 159(3): 680-686 DOI: 10.1111/ibi.12469

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