I know it's unusual but not unheard of. We are suffering from a plague of raptors (sparrow-hawks, buzzards and even peregrine falcons) which have taken 33 white doves so far and we are desperate - as are the remaining pigeons!

Can you suggest a suitable dye which will work on live pigeons to turn them into something the hawks don't recognize - ideally green, blue, red, orange. Obviously pigeon friendly - and water-proof enough that we don't have to re-dye them every time it rains.

We would be very grateful if you have any ideas.

The first priority is that the dyes should not be toxic to the pigeons, and the second is that its application should not be traumatic for them. The best recipes for dyeing feathers which are no longer on the birds call for boiling water, which will not do at all.

The safest dyes to use are food colorings. The easiest way to apply them is in an air brush. I've seen airbrushed food dye being used in costuming people, with very effective results. I imagine that the food dyes were at full strength, as they came in little bottles from the grocery store, but I do not know for certain. Food dyes are acid dyes, and will do a good job of dyeing feathers permanently if applied in boiling water, but it is worth trying to see how well they will work at safer room temperatures. They are apt to run in the rain, though.

The main alternative would be paint, rather than dye. Paint is a combination of a pigment with a glue, whereas dye has a natural affinity toward the fiber it is used for. Many paints do not require the use of heat at all. A water-based paint, would, of course, be less toxic than an oil-based paint. Fabric paints are softer and thinner than artists' acrylic paints, and therefore would have less effect on the function of the feathers in flying. Many fabric paints will stay permanently without heat-setting, as long as they have enough time to dry before they are rained upon.

Since both hair and feathers are made of proteins, hair dye should also be considered. I did not think of this immediately due to my bias towards textile dyes, but this is probably the best solution overall. The toxicity of hair dye should be low, and it does not require heat to set it. It is also quite easy to find in local shops. The darker hair colors would probably be more suitable than the brilliant colors of food dyes for rendering the doves more difficult to see. The food dyes can be mixed to make duller shades, of course, but having the dye ready-mixed in dark brown would save trouble.

As a biologist, I must ask whether you have any evidence that a change in color will affect the hawks' perception of their prey. Is one color better than another? Without data, I would have guessed that any bright color might be a risk, and that the goal would be to dye the pigeons a darker color that would be more difficult to pick out against their background, ideally one with splotches or bars to break up their outline.

This is certainly an interesting question. I would be very interested in whether dyeing turns out to be helpful.