c4countdown

The Collared Dove is a bird that I am growing to like more and more. I used to mistake them for pigeons, but I have now reconciled the error of my ways. Indeed, it is a common trap to fall into, but the collared dove, the rock dove, the stock dove, and the wood pigeon are all different species and it would seem that urban pigeons are various hybrids between these forms.

One of my favourite birds, though, is the common robin.

Thoughts?

Richard Brittain wrote:Indeed, it is a common trap to fall into, but the collared dove, the rock dove, the stock dove, and the wood pigeon are all different species and it would seem that urban pigeons are various hybrids between these forms.

If they're different species, how are there hybrids?

Pardon?

Richard Brittain wrote:Pardon?

Don't people define animals to be of the same species if they can breed? A hybrid can presumably only occur if they can breed. Not sure it works as a sensible definition myself (presumably the attempt is to categorise types of animal) but I know nothing about the subject.

Yes, I think that is what Reams was trying to imply also, but it is, sadly, erroneous. A hybrid can be between two species, and many examples exist (ligers, mules etc.). Anyway, I have no interest in this sort of scientific terminology. It was down to one guy 200 years ago to decide whether this creature is a different species to that creature, or a different 'race' of the same species. I don't care for such trivial categorising because it tends to limit the complexity of life. But for the record, the collared dove, the stock dove, the rock dove and wood pigeon are all officially classified as distinct species, yet are quite similar (of the same 'genus'), and all can interbreed to produce hybrids, which accounts for the great variety of what we know as 'urban pigeons'.

It does seem strange that each of these quite similar types of dove is classified as its own 'species', whereas all the hugely different breeds of dog are in fact classified as the same species. As I said, it was just down to one random guy who attempted to categorise these things in his own way. There doesn't seem to be a huge amount of logic behind the official system.

Who was the guy?

Not sure. It was probably many different random guys actually, who added different bits at different times.

I thought a species was defined by the absence of reproductive barriers, i.e. it may be possible for members of two different species to breed, but this might not be true for the children of such a union (male ligers, I believe, are infertile). Thus speciation (the formation of new species) almost always occurs by gradual genetic drift, typically of an isolated population, and only very rarely by hybridisation.

Linnaeus had the idea of categorising species into genera, orders, etc all the way up to kingdoms. The modern system of biological classification is based on the same idea, but a lot of the species and classes are completely different to what Linnaeus came up with, which is hardly surprising considering he was working in the 18th century.

Richard Brittain wrote:Yes, I think that is what Reams was trying to imply also, but it is, sadly, erroneous. A hybrid can be between two species, and many examples exist (ligers, mules etc.). Anyway, I have no interest in this sort of scientific terminology. It was down to one guy 200 years ago to decide whether this creature is a different species to that creature, or a different 'race' of the same species. I don't care for such trivial categorising because it tends to limit the complexity of life. But for the record, the collared dove, the stock dove, the rock dove and wood pigeon are all officially classified as distinct species, yet are quite similar (of the same 'genus'), and all can interbreed to produce hybrids, which accounts for the great variety of what we know as 'urban pigeons'.

It does seem strange that each of these quite similar types of dove is classified as its own 'species', whereas all the hugely different breeds of dog are in fact classified as the same species. As I said, it was just down to one random guy who attempted to categorise these things in his own way. There doesn't seem to be a huge amount of logic behind the official system.

Alas, your science is erroneous. Paul's definition of species is right. Dogs are indeed the same species (although one might question the anatomical possibility of a Great Dane/Terrier cross), and the various pigeons you name are different species. It's true that higher categories such as genus are artificial, but no current scientist would defend them as anything else -- they're just a convenient way to say what sort of organisms you're talking about. More recent work in cladistics puts the "tree of life" on a much firmer genetic footing, and a lot of traditional Linnaean taxonomy has been reworked in the light of that.

No doubt Jesus had his own reasons for introducing these apparent genetic similarities.

No. This isn't actually correct. It is true that often hybrids between different species are sterile, but it is not always the case and it doesn't seem to apply with many birds.

To quote Wikipedia (http://en.wikipedia.org/wiki/Hybrid_%28biology%29),

'Hybrids between different species within the same genus are sometimes known as interspecific hybrids or crosses...

'The offspring of an interspecific cross very often are sterile.'

The important term here is 'very often', not 'always'.

If you believe what you read, the common domestic chicken is the result of a hybrid many years ago between Red Junglefowl and Grey Junglefowl, independent species.

Also, often the hybrid species can breed with one or both of its forefathers. For example, a female mule can breed with a donkey. Therefore, there are many possible variations which can occur in resulting offspring.

Also: http://en.wikipedia.org/wiki/Lonicera_fly

Richard Brittain wrote:No. This isn't actually correct. It is true that often hybrids between different species are sterile, but it is not always the case and it doesn't seem to apply with many birds.

To quote Wikipedia (http://en.wikipedia.org/wiki/Hybrid_%28biology%29),

'Hybrids between different species within the same genus are sometimes known as interspecific hybrids or crosses...

'The offspring of an interspecific cross very often are sterile.'

The important term here is 'very often', not 'always'.

I think this is what's known as "hedging your bets" (which Wikipedia is often guilty of.) Anyway, the birds you named are not in the same genus. Intergeneric hybrids can occur but it's unusual amongst animals. Maybe it happens in birds, which would answer my question, although I can't find any sources either way.

So, you agree with me. Good.

Richard Brittain wrote:So, you agree with me. Good.

I don't know how you managed to infer that, but whatever keeps you happy mate.

Do you trust the Encyclopedia Britannica? Their definiton (http://www.britannica.com/eb/article-9041687/hybrid) of a hybrid states that: 'The parents may be of different species, genera, or (rarely) families.'

So, this does answer your question 'If they're different species, how are there hybrids?' The answer is 'Hybrids can clearly occur between different species, genera and even occasionally families.'

Your point that the birds I mentioned are not of the same genus is half-correct though, I admit I made a mistake there. The Stock Dove, Rock Dove and Wood Pigeon are all of the same genus (Columba) but the Collared Dove is of a slightly different genus (Streptopelia). They are all of the same family (Columbidae), and we have just confirmed anyway that inter-generic hybridisation is possible (assuming you trust the Encyclopedia Britannica).

In other words, you agree with me now.

Richard Brittain wrote:Do you trust the Encyclopedia Britannica? Their definiton (http://www.britannica.com/eb/article-9041687/hybrid) of a hybrid states that: 'The parents may be of different species, genera, or (rarely) families.'

So, this does answer your question 'If they're different species, how are there hybrids?' The answer is 'Hybrids can clearly occur between different species, genera and even occasionally families.'

Yep.

Richard Brittain wrote: Your point that the birds I mentioned are not of the same genus is half-correct though, I admit I made a mistake there. The Stock Dove, Rock Dove and Wood Pigeon are all of the same genus (Columba) but the Collared Dove is of a slightly different genus (Streptopelia). They are all of the same family (Columbidae), and we have just confirmed anyway that inter-generic hybridisation is possible (assuming you trust the Encyclopedia Britannica).

In other words, you agree with me now.

Yep.

More bird facts please?

One magpie will give you sorrow, but two will give you joy.

The common pheasant, stalwart of English culture, was only actually introduced here about 1500 years ago, and originates in Asia. (I'm not sure if I believe this)

Richard Brittain wrote:One magpie will give you sorrow, but two will give you joy.

Oh, like lesbians?

Richard Brittain wrote:The common pheasant, stalwart of English culture, was only actually introduced here about 1500 years ago, and originates in Asia. (I'm not sure if I believe this)

Next you'll be telling me that the Royal family, that other stalwart of English culture, were imported from France less than 1000 years ago!

Madness.

Corby brought up the subject of ducks in another thread, and on that subject, one of the most striking and brilliant ducks of the British Isles is the Mandarin Duck, which can be found in lakes throughout the country:



These ducks are another import from China, but they are widespread in Britain. I have seen quite a few of them around, they are quite a sight to behold, normally found singly or in a pair near a larger congregation of mallards or other more common ducks.

Richard Brittain wrote:Corby brought up the subject of ducks in another thread

Did not! It was O'Donnell.

An interesting fact* is that ducks sleep in formation. They're apparently capable of shutting down one half of their brain whilst keeping the other fully active, so the outermost ducks can keep one eye open and watch for danger while the rest sleep properly. Occasionally they'll swap positions to allow the "guard ducks" to have a proper snooze. I've never observed this behaviour myself, but I'd like to think that this is what ducks get up to when we're not looking.

*told to me by a notorious bullshitter, so it could easily be an excellent lie

I've never actually heard that, but it makes sense.

Richard Brittain wrote:I've never actually heard that, but it makes sense.

Does it? Surely if there's enough of them, the guard ducks could be fully awake and then once they've done their shift go to sleep properly themselves.

Edit - http://www.straightdope.com/classics/a990702a.html - Apparently it is true, but ducks' quacks do echo before anyone is retarded enough to ask.

Just for the record, The Straight Dope is an awesome thing, and I suggest everybody follows in my footsteps and reads every article ever.