Local movements of the small species are still best served by traditional VHF beeper tags, although if recording presence/absence (for example nest feeding visits at a colony) then Coded VHF tags can help prevent missing events. For more information about the advantages of Coded VHF please see "Coded Tags or Beeper Tags?" on our FAQ page.
To study migration routes of species too small for satellite/GPS tags, Geolocators are better, whereas coded VHF tags are best for recording birds passing through migration points or when using aircraft to look for birds. Alternatively, if studying waterbirds, you may be interested in the depth and duration of dives and the temperature of the water, presence in the water etc. Our Temperature Depth Recorders collect data on just that, and can be combined with Geolocators to give both dive profiles and migratory movement. For more information, please see Geolocators & Temperature/Depth Recorder tags.