In a paper in the Journal of Analytical Atomic Spectrometry [JAAS] (in case you haven’t read your latest issue), I learned that bird migration patterns in Europe are still kind of hazy, despite the long standing and often intense interest on the part of birders and conservationists. It’s just not an easy problem. Not being a birder myself, I didn’t know this, nor did I have much interest in migratory patters of birds prior to bird flu. Now many of us have a newfound interest in it. Which is why a new method to figure out migratory bird patterns caught my eye.
The usual methods are both labor and resource intensive. You can band the birds and do a capture - recapture statistical analysis, or try putting little transmitters on them or even do a complete census of migratory stop-over areas. A recent idea is to use chemical analyses to indicate a geographic origin, but the more common elements (carbon, hydrogen, etc.) haven’t been very precise, geographically, and use of trace elements frequently required invasive techniques, for example, bone samples. One of the more interesting trace elements is strontium, which often takes the place of calcium in bone and is also potentially informative about the location where a bird spent time because it also reflects geochemistry. For all the chemical analyses, it’s not the amount of strontium itself, but the ratio of stable isotopes, in the case of strontium, the isotopes strontium-87 and strontium-86.
What’s an isotope ? The word comes from the Greek iso- for "the same" and topos, for "place." Chemical isotopes are chemical species that are "in the same place." The location referred to is the same place in the periodic table of the elements. Different isotopes of the same chemical species (atoms of the same element) have the same chemistry, which is what their location in the periodic table says, but differ in another way, their atomic weight. By examining the ratio of the number of atoms of strontium of two different atomic weights, weights 87 and 86, information is gained on the geochemistry of the location where the bird spent time.
Having to use bird bone is not ideal. Bird feathers would be better. And that’s what the paper by Font et al. in JAAS did — measure the strontium isotope ratios in the feathers of a bird species, the Sedge Warbler. There isn’t a lot of strontium in the feathers of a bird, although what there is seems to reflect the location where the bird was when it grew its feathers. Using highly sensitive analytical techniques (hence the description of the method in a specialized analytical chemistry journal), the authors were able distinguish birds from different locations. But there seems to be a long way to go before this method would be practical and well enough specified to be useful (see the discussion section of the paper).
The many obstacles notwithstanding, the autor naturally has high hopes for her method :
"By determining migration pathways, the arrival of potential vectors of diseases from infected areas can be anticipated," said Font. "Knowledge of migratory routes also helps evaluate the likelihood that individual avian influenza outbreaks could be related to migratory bird movements rather than anthropogenic activities, such as poultry movements, which are believed to be the main vector of avian influenza in most outbreaks," she added. (Royal Society of Chemistry news release)
It would be nice. Maybe someday. What this demonstrates, I think, is that Necessity is the Mother of Invention. We know too well that not all of Necessity’s offspring grow up to be productive members of society. This one seems still to be in pre-school.
