Sunday, 25 May 2014

How to make Razorbill colour rings

Making Razorbill colour rings - Introduction to the problem
Skomer has had a colour ringing study on adult Razorbills (Alca torda) for the past 44 years. It seems to have worked really well, despite the obvious problems of them wearing the rings away. Razorbills walk on their tarsi, and so any rings placed there get worn very quickly. This is why the metal rings used are specially shaped, to reduced the wear that occurs to the inscribed unique number. 

Razorbills walk on their tarsus.
Rings must be shaped to avoid excessive wear.

Part of my job is to catch new adults each year and colour ring them. This means that the numbers of colour ringed adults remains relatively constant, and adult survival statistics can be calculated. These rings do not come preformed, and I therefore needed to make them myself. 

Having never made colour rings before, I tried to do a bit of research to see if there was any information on making triangular colour rings. I failed to find any, and so thought this blog post might be of use to anyone else wishing to make Razorbill or Guillemot colour rings. It took a bit of trial and error, but I've found the following method is the best for making rings of consistent size and shape.

Making the colour rings:

Step 1
Use a closed Razorbill special and push it as far up a pair of pliers as possible. I used needle nose pliers, but a pair with more square edges would be long as the Razorbill special fits over them. 

Mark the point at which the ring fits across the pliers. This will give you a gauge of where the pliers match the internal width of a Razorbill special and ensure all the colour rings you make have the same internal dimension.

1) Push Razorbill special onto the pliers until they can go no further
2) Mark the point at which the ring reaches

It's important to mark both sides of the pliers at this point, and to mark them in a form that wont get rubbed off when submerged in boiling water. I scratched the mark in with my penknife. Make sure the marks made on both sides of the pliers line up (seems obvious but I did it wrong the first time). You can then see where the colour ring plastic needs to go whichever way you hold the pliers.

Step 2
If you have to cut your own colour ring strips (as I did), then 45mm seems to be the best length. This allows enough spare for a good overlap, but ensures the internal triangle doesn't become too large. When placing 2 rings on 1 tarsus the width must be less than 8mm. Razorbill tarsi are remarkably short and anything wider than this will not allow 2 rings to fit on one tarsus. Make sure the ends are rounded off so there's nothing sharp for the bird to catch its leg on.

Colour ring strip: 8 x 45mm should make good rings

Step 3
Line this strip up with both marks on one side of the pliers, leaving a little bit poking out of one side (picture 4). This extra bit will form a small overlap inside the finished colour ring.

3) Line up with marks on 1 side of the pliers

Then ensure the strip is lined up with the marks on the other side of the pliers. This should mean that the plastic is perpendicular to the mid-line of the pliers and will make it easier to line the edges up with each other when you form the ring.

4) Ensure the strip is perpendicular to the mid-line of the pliers

Step 4
Now heat the strip in boiling water until it goes soft and malleable

5) Heat in boiling water until soft

Step 5
Once the plastic is soft, quickly wrap it around the pliers to form an "e" shape. Ensure all the edges of the plastic are parallel so there is no twist in the ring. With these tapered pliers it was easy to follow the line of the pliers so the edges didn't line up. Make sure this doesn't happen.

Also make sure there is quite a bit of extra sticking out beyond the curved part you've just formed. This extra will form an overlap once the colour ring is finished.

6) Wrap the plastic around to form an "e"

Step 6
Once the plastic has cooled slightly (enough to hold its shape), readjust the grip to bring the two ends together. Again, make sure all the edges are lined up and there is no twist in the ring.

7) Readjust grip to bring 2 ends together

Step 7
This is the tricky bit that takes a bit of practise to form a nicely shaped ring. Reheat the plastic until it's soft. Then bring it out and quickly squeeze the two sides together, applying even pressure, to form the triangular shape. I couldn't take a picture of this as it requires two hands, but it's quite obvious when you get it right.

Make sure that you fold the extra bit of plastic up to form the overlapping section seen in picture 8, on the left of the ring. If you apply too much pressure then this extra bit causes a kink in the internal triangle. Too little pressure, or uneven pressure, and you don't get a good triangular shape. Also if you apply the pressure in the wrong direction then you end up with a right angle triangle rather than an isosceles triangle. As you're pinching the two sides, try and get the top of the triangle over the mid-line of the pliers. This should ensure you form a nice isosceles shape, rather than a triangle skewed to one side.

This part took a bit of practise to get right, so try it a few times to get comfortable with the technique. Due to the shape of the pliers, I sometimes found that one side of the bottom of the triangle was the right width, but the other was too thin because it had followed the taper of the pliers. In this case, turn the formed ring around and force the pliers into the thinner side. Then gently reheat and repeat the pinching process. This should mean that both sides of the triangle are the same width and match the internal dimensions of a Razorbill special.

8) Pinch sides together to form isosceles triangle

Final Step
Repeat steps 3-7 until you are happy with the shape. Compare the finished colour ring to the closed metal ring to make sure the shape is correct, and the internal dimensions are the same as the Razorbill special.

This method ensures that the bottom of the ring (the part at the back of the Razorbill tarsus) is double thickness, and should increase the time it remains on the Razorbill. Some of my study adults have lost colour rings, presumably because they have been worn through and fallen off. By making the bottom double thickness, it extends the time it will take for the bird to wear them through, and so they will remain on the leg longer.

9a) The finished ring with a double bottom layer
9b) The finished ring with an overlap for gluing

The extra bit of plastic left outside the pliers in Step 3 forms the internal fold, and ensures the double thickness extends across the full width of the bottom of the ring. The extra plastic left in Step 5 produces the overlap seen in picture 9b. This can then be glued easily after placing the ring on a Razorbill, and ensures the ring cannot open up after release.

I also recommend making lots of spare rings to take into the field, ideally of variable widths. Some of the Razorbills I've ringed have exceptionally short tarsi and I've had to pick narrower rings to go on these birds.

I hope this has been informative for anyone who wishes to use colour rings on Razorbills. The technique can also be used to create colour rings for Guillemots when using a closed Guillemot special as the template ring.

Please feel free to leave comments if any of this doesn't make sense, or you have any suggestions for improvements to the technique. I will have to do this for a few seasons so any improvements would be much appreciated.

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