Classificiation of bird species, and a question

[HouseFinch]

In reading various bird guides through the years, I've noticed that species of birds tend to be merged, split, and sometimes merged again, and I wonder, why the confusion? Technically, couldn't scientists analyze the DNA of these 'conflicting' birds, and see for a fact whether or not they are the same species? An example of this would be the Gilded Flicker and the Northern Flicker: to me, they appear to be the same species, and were considered so for many years. Why the change? I'm no ornithologist, nor any type of scientist for that matter, so I apologize if this question is completely dense. 8-P

And, I don't want to raise any hackles here by bringing up bird flu, but I have a purely hypothetical question: theoretically, what would happen if bird flu entered the States and spread through its wild birds? How would this affect birders, and our hobby of feeding our feathered friends?

[dendroica_john]

On the question of merges and splits, I think there are two reasons. One is that DNA studies have not been done on all species because these are expensive and require researchers to do them. There are far more potential bird species than researchers. The second reason is that the concept of what a species is and where to draw the lines changes, sometimes favoring greater numbers of species and sometimes favoring fewer. The lines are drawn based on morphology, breeding patterns, and now DNA. Opinions change and sometimes evidence in one study gives different results from that in a previous study. Lying behind that is that speciation, while real, is somewhat artificial and is certainly not static.

On the bird flu... It should not affect backyard bird feeding since most of the spread has been among waterfowl and gamebirds.

[tomjenner]

There are differences between individuals, between different races, different species etc. DNA analysis can tell you how much genetic difference there is between two populations, but not the significance of that difference. Hypothetically, there could be a very minor difference between two populations that is controlled by only a few genes, which results in a physical characteristic or behaviour that means that the two cannot breed. In this case a minor genetic difference causes speciation, whereas a much greater difference between two other populations may not. A big genetic difference is of course more likely to mean that two populations are distinct species, but field work is also needed to confirm it.
So if the various different forms of flicker were tested, they would all be genetically different, but we would not know what the difference signifies without detailed fieldwork. Traditionally, species were determined more by whether or not they could interbreed and produce fertile offspring. In allopatric species (those that live in different places) this was sometimes done by seeing if they responded to each other songs and studies of that sort. Speciation based on this type of procedure is known as the Biological Species Concept. Nowadays, many people are now following the Phylogenetic Species Concept, which is more based on the physical and genetic differences between populations. People who follow this approach might be more willing to separate a species based on DNA data.
Personally, I think that DNA information is a valuable tool, but one that is only valid if used with field studies. I'm not much of a fan of the Phylogenetic Species Concept myself.

Tom

[Xenospiza]

It's even more complicated with DNA...
First of all, all of it is statistics: so the larger the sample size, the smaller the errors. Many papers using very small sample sizes have been followed to announce splits.
Much of the work is done on mitochondrial DNA, which is always inherited along female lines (so you get "half the information"). It has been shown that mitochondrial DNA can lead to wrong conclusions, because one type can be "conserved" better than the other. Other genes can lead to other conclusions – if multiple genes lead to similar conclusions, the conclusions are stronger.
DNA can show many interesting things about the evolutionary history of birds, but delimiting species should not be its goal (even though that's the thing birders want to hear).

[Xenospiza]

Considering avian flu (I've noticed suddenly Americans are stirring in this discussion – has it been in the news recently?), check the "Avian flu towards the UK" thread!
If the federal and state governments would be smart, it should have no effect on birdwatching (only on farming and poultry exports)... but what's the chance of that?

[HouseFinch]

Considering avian flu (I've noticed suddenly Americans are stirring in this discussion – has it been in the news recently?), check the "Avian flu towards the UK" thread!

Unfortunately, yes, it has been on the news a lot over here: personally, I think they are overemphasizing it, and making people paranoid. So typical for the media. I'm not too worried, I just thought I'd bring up that question, since I was pondering it the other day.

So apparently DNA doesn't have all the answers then: that makes sense. Analyzing strands of genetic code does seem as though it would be a painstakingly difficult process. But in a way it's annoying for us birders, if every so often bird species are changed, split, and merged, meaning we have to buy new guides every ten years. :'D

[Tim Allwood]

The Sibley and Monroe classification was based on DNA-DNA hybrisation techiques - basically the closer the relationship between species, the better their opposite strands of DNA match when 'mixed' together. Results were better at higher taxa levels i think. Has recently been superceded by a taxonomy by Joel Cracraft (I think) that changed rather a few things... this Cracraft taxonomy isn't in use in birding circles.

Tim

[Xenospiza]

In birding circles, most people are annoyed by each change involving the order in their guide!