Read our regular wader tracking studies updates from Australasian Wader Studies Group for Oriental Pratincole, Little Curlew and Eurasian Whimbrel and from Australasian Wader Studies Group / Victoria Wader Study Group Far Eastern Curlew Project.
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Traditionally gathering bird data and tracking their movements, had been done by field observation and ringing recoveries, where a single metal identification ring was fitted to the leg of a bird. This resulted in information about movements and site fidelity being available but this information was only forthcoming from the ring if the birds were re-caught, or found dead and the ring returned.
More recently colour ringing has been used a great deal more. This means that individual birds can be recognised in the field by observers. This increases the potential for information gathering as the bird can be reported without having to be trapped or die.
The idea of a simple colour ring or combination of rings has been added to by using flags that display an identification code in letters and numbers which can be read by field observers using optical equipment. This negates the need for several colour rings to be worn in combination but they are sometimes used in conjunction with one another.
If you then add to this the use of electronic tracking devices then the amount of information that can be garnered is very high. Not only can you discover where a bird is you can tell how long it has been there, how it got there, and by which route.
But these new developments are not universally loved methods of data collection. Many people dislike the birds being adorned with what is euphemistically referred to as ‘bling’ (many coloured rings and flags) and/or electronic devices. In some cases the argument is purely aesthetic; who wants to see wild birds with brightly coloured, unnatural rings on them? In other cases the fear is of a more sympathetic nature where people are worried that the device may in some way harm the bird, upsetting its usual routines or even killing it.
It should however be born in mind that the use of these devices has been much studied with the birds’ welfare at the centre of the studies. There are strict guidelines for what equipment can be used on a species based on its weight and size. Here are some points to consider when making up your mind.
- Researchers care as much about the health, safety and welfare of their subjects as anyone, perhaps more so, their work depends on the bird’s survival and well-being.
- If the devices affect the birds’ behaviour and survival chances then the data is useless, so every effort is made to prevent this.
- Conservation is increasingly important as suitable habitat is shrinking across the planet; conservation can only be effective if we have the information we need to make the right choices and decisions. There is much that can be learned that cannot be done by other methods of investigation.
- Many important discoveries have already been made using tracking devices.
One such discovery was the case of the incredible E7, a female Bar-tailed Godwit of the baueri race. It was satellite tagging that finally proved that these birds fly nonstop from Alaska to New Zealand some 11,700 km. Whilst this is awe inspiring it is perhaps not essential to know this in terms of conservation, after all we have suspected it for some time, knowing for sure makes little difference as there is not a lot we can do to help in this case. However, much more importantly, the same bird’s trace, along with several others of its kind, showed that the entire Alaskan population of baueri Bar-tailed Godwits travel back to Alaska to breed via the Yellow Sea region, an area that was being destroyed at an incredible rate threatening the very existence of these and many other birds. The information gathered from the tagging was used to influence the Chinese Government, among others, persuading them that they had a responsibility to halt the destruction to save the lives of many millions of birds and prevent the extinction of the Alaskan godwits and also perhaps Nordmann’s Greenshank, Spoon-billed Sandpipers and others too. Without this proof they may not have listened.
There are different sorts of tag available. Some are powered by battery, others by solar power, some are attached by harnesses, some by glue to the feathers and some (as in the case of E7) are surgically inserted into the body cavity.
A geolocator is a device that records the location of a bird but the drawback of these devices is that the bird needs to be recaptured to retrieve the data. The device gives information on migration; timing, duration of stop-overs and also pinpoints breeding and non-breeding locations
VHF (Very High Frequency) radio trackers can be detected by using mobile or fixed station receivers. The fixed statins will record whenever a transmitter enters their range but mobile receivers stations can be taken to any location in order to search for tagged birds; they can even be used from aeroplanes.
VHF can be labour intensive, depending on the tracking method used, and requires more logistical planning than satellite based studies, mainly due to the manual tracking efforts that may be required. The effectiveness of transmitters is affected by the need for manual tracking, the transmitting range and battery life of the unit become crucial. As they rely on batteries which have a finite lifespan there is a nice balance to make between the two, the greater the range the more power is required therefore the shorter the battery life and of course vice versa.
With regard to location accuracy VHF is the least effective although, if the radio signal leads to a sighting, it becomes very effective indeed, down to 5m accuracy.
Satellite telemetry provides opportunities to follow the movements and migratory routes of waders that are not possible with any other technique.
GPS (Global Positioning System) and PTT (Platform Terminal Transmitter) trackers send data via satellites which can be downloaded to remote computer terminals. GPS is the most accurate with an error of 10-20m.
PTT transmitters provide a nearly continuous history of a bird’s movements, revealing detailed information concerning the migration route, rate of travel and stopover duration during flights that may cross entire continents and oceans. They are less accurate than GPS with accuracy to within 100-200m.
The longevity of solar-powered satellite-based transmitters allows long-term studies that can determine annual fidelity to specific migration routes and stopover points, data which may help identify migration hotspots.
With thanks to the following photographers: Queensland Wader Study Group