Do satellite tags hinder our woodcock?

One of our kind sponsors recently asked whether the satellite tags we use to track our woodcock ever hinder them in terms of flight, feeding or courtship.

Here was our response:

With regards to the potential impacts of the tags upon the birds: these are clearly questions we are constantly asking ourselves.

Obviously the welfare of the bird is paramount and the continued use of the tags depends entirely upon their safe use.

Additionally, it is important to us that the tags are comfortable and have no impact upon the bird as we are seeking to record normal behaviour that is unaffected by the presence of the device.

Tags are under 3% of the birds body weight. The 3% figure is a benchmark used by most ornithologist when considering the added weight of a tracking device. It is widely agreed that at this level, the tag's impact will be minimal.

Nevertheless we need to be certain that the tag (both its weight and means of attachment) poses no detrimental effect upon the bird. This is understandably hard to measure.

However, we have been able to re-capture three of our tagged birds in subsequent winters - these bird's tags had stopped transmitting, probably as the result of 'battery issues' and so were removed and re-used.

Having a bird in the hand, that had carried the tag for a year or more, allowed us to check for physical signs of wear or damage resulting from the tag. In all cases, there was no evidence of this.

Additionally, the birds were all still healthy weights, similar to those when first caught, indicating that the tag was not impacting upon fitness or the ability to feed.

Please help us continue our woodcock research

 

How do we interpret the data we receive?

The satellite tags we use to track our woodcock provide us with data every three days, with the information presented in tables like the one below:

The columns highlighted in red show the information required to build a ‘flight map’ on Google Maps, such as the one on the Woodcock Watch website.

'Program' is the unique program number that our project has been allocated and ‘PTT' is the identification number for each bird’s satellite tag.

'Location class' provides an indication of the accuracy of the data. A number denotes a position which is accurate to within 1km and a letter indicates a margin of error too large to display on the map.

All the data we receive from these files is automatically processed by a computer program every 24 hours. As new files are received the program scans them for the appropriate location data so the map you see on the Woodcock Watch website is updated accordingly.

Simple!

Please help us continue our woodcock research