What are Coded Tags?

Coded tags are VHF tags that send codes rather than simple beeps, allowing for more than 200 tags to share the same frequency.

To explain the advantages of coded tags, here is an example. Consider if you have 40 birds that are returning to a colony to feed their chicks, and the visit time is 2 minutes. With beeper tags all on different frequencies, the logger would listen to each one for at least 5 seconds each (5 x 40 = 200 seconds), and loose about 5 seconds (switching between birds) so 205 = 3.4 minutes. Therefore it takes more than 2 minutes between logging the same bird and in that time the bird could have come in, fed its young and left without any possibility of the event being recorded.

Lotek's coded nanotags are all on the same frequency, therefore the DataSika logger (or more sophisticated SRX Loggers) can be listening for all tags at the same time, and would not have missed that event. If two tags are around at the same time, their pulse intervals are different to reduce congestion. If you are considering large numbers of birds there is another option to minimize congestion, so please ask.

Lotek's coded nanotags get over this, and the DataSika logger (or more sophisticated SRX Loggers) can decode the signals. It is worth noting that tracking to find the location of the animal is less easy with coded tags, so really this is best designed for presence/absence studies.