Just how important is supplementary food to the success of the Red Kite reintroduction?

Arron Watson

When I first became involved with this project, I was told that part of it would involve measuring the stable isotopes of feathers. My reaction was probably the same as most people’s…what’s that? I read a few journals and was amazed at the potential of what can be represented in terms of evidence to a scientific investigation, or proof of the past; so what exactly is it?

Isotopic elements are found in everything from food to soil, from plants to humans. Being able to understand the different amount of these elements allows researchers to compare the amounts or ratios through samples of dynamic (blood and muscle) and fixed (hair, and feathers) tissues from the organisms that are involved. The heavy isotopic elements which include carbon and nitrogen can be analysed as well as lighter isotopic elements, like metals, which can be looked at to understand if pollutions has been absorbed. This sort of investigation in Australia has been used on aquatic insects and looked at metal levels in their blood that related to the water pollution in the environment, thus giving evidence to suggest there was pollution within that area where mining had been prevalent.

Other examples of investigations include looking at species food chains or food webs, predator-prey interactions, migration of birds and mammals and looking in to the past at fossil samples to find out what the planet was like thousands of years ago. There are other important uses of SIA for solving crimes within the police – this is through the use of forensics and being able to analyse bones and hair, archaeology and geology, climate change and hydrology but – how does it work?

Tiny samples (0.2-0.09 of a gram) of each individual are taken – whether it be hair, feathers or muscle  -that are then placed in tiny capsules and put inside a machine called a mass spectrometer. This machine separates all of the atoms and is able to decide how much carbon, nitrogen, oxygen and hydrogen there is; along with deciding what trace elements there are like different metals. The results are then placed within a computer which can then compare the different samples and decide what the information means.

For example, if in my investigation we want to know what the Red Kite has been eating by comparing the carbon ratio of say chicken to the carbon ratio of a rabbit and see which ratio is prominent within the feather, we can then determine if they have eaten wild, or supplementary fed foods just from the elements inside the feather (and a very expensive piece of equipment). The info-graphic below gives an idea of how the basic process works without going into greater detail. Later in my blog I will be able to show you some basic graphs to gain a better understanding of the depth of information that can be gained from such a small sample.

The potential for this investigation could be able to understand what exactly a Red Kite has eaten for the past X amount of time, across a long transect of locations including Scotland, the midlands and the South of England. It is thought that not many, if any, people feed Red Kites in the Highlands compared to a large amount (as discussed in my previous blog) of supplementary fed in Reading. This would and should mean that the results from the SIA will show different isotopic ratios because of their different diet, however we will not know until week 4 when I have interpreted the results.

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