> [Birds] are ... characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
Notice that when you put all of those traits together, you get the ability to lead a lifestyle centered around long-range migratory flight.
One or a few species evolved this particular set of traits, which gave them the ability to forage incredibly long ranges in search of food, in a landscape that was—at the scales other dinosaurs could travel—increasingly inhospitable to life. This small set of species then took over the habitats of every other dinosaur species as they died out, and then speciated into all modern birds. It was a sort of evolutionary bottleneck point.
In other words, "birds" are essentially defined as the set of theropod species that survived the K-T extinction. Birds happen to all have many unique traits in common, because these traits were adaptive through the rapid change of environment that killed off the other dinosaurs.
> "birds" are essentially defined as the set of theropod species that survived the K-T extinction
The problem with that is that this bird would not be considered a bird, since it didn't survive the K-T extinction. It is considered a bird because it is bird-like enough. (and the concept of "bird" is a man-made category...and there would be a lot of blurriness if you look at species that lived at the same time as (other) dinosaurs.
You're right, insofar as "bird" is not jargon, or in 1:1 correspondence with jargon, in any scientific discipline. There's just theropods, some of which happened to survive, where people call the descendant species of those particular theropod species birds. There's no rule specifying whether those theropod species themselves are birds, or whether species that are 99% like them but happened to die off due to pure bad luck are birds, etc.—because we don't need such a rule for anything.
If we did, though—if "bird" was jargon under some branch of science, the way that "fruit" is jargon in culinary science†—then I would guess that the criterion for it would be something like "a theropod with adaptations that would make it likely to survive the K-T extinction, all else being equal", making both the ancestor theropods to current birds qualify, as well as the bird in the article. But, well, nobody needs that definition for anything, so it can't really be argued what the definition "really is."
"Birds" is a taxon (Aves is the scientific name for it). In modern biology, all taxa are defined to be "monophyletic lineages" or "clades", which means that in principle they comprise one ancestral population and all descendants. No taxon would be defined nowadays as you define it since your definition does not necessarily identify a clade. A valid monophyletic taxon might be coincident with a set of organisms identified by a definition such as yours, however.
Although, interestingly the article describes the find as belonging to an ancient group of toothed birds, so perhaps the Wikipedia description needs a tweak?
All toothed birds are extinct. Some birds today have serrations on their beaks that might look like teeth, but they're not really teeth in an anatomical sense.
Also, we only consider the extinction to be "over" (the point at which we can declare who is and is not a survivor) when the only theropods left were birds, so this definition is circular. This is the problem with trying to derive necessary and sufficient conditions for things like "birdness", the concept was constructed by pattern matching, not analytically, so rarely will an analytic definition capture everything that the common sense understanding encompasses.
We're not talking about the same "pattern matching" because even those examples are pattern matching. You have breeds of dogs and a dog is either one breed or another or it's a hybrid/mutt. But at what point in the process of creating a new breed do you switch from handling hybrids of existing breeds to handling purebreds of your new breed? No single generation seems like it could be enough to make the difference, since the puppy is just as similar to its parents as the puppies of any other generation, but on the scale of many generations, a new breed clearly emerges. It's analogous to the paradox of the heap [1].
Derek Parfit's Reasons and Persons engages with this problem as it applies to personal identity with his "spectrum cases".
That was kind of the point of my definition, actually—it's easier to predict what type of thing is a bird if you think of "bird" as "the clade rooted on all the theropods that fit through a particular evolutionary sieve" rather than a category with certain characteristics. Not all modern birds have those characteristics. But those characteristics are what allowed the prototypal "birds" to survive where other dinosaurs did not. Their descendants went on to adapt in various other ways, but we still consider them all "birds" for reasons of genetic lineage back to those original birds.
Yes, they evolved later (generally under non-mammalian island biogeographies which produced evolutionary pressures which meant that being large and foraging nocturnally had benefit over retaining flight).
This happens all the time -- imagine the evolutionary pressures on proto-cetaceans. Now imagine writing a comment discounting the benefits of land-dwelling because some paths returned to the sea.
All birds had a common ancestor species. Anything that's a descendant of that ancestor species is a bird.
The actual ancestor hasn't been found, but it can be determined by genome studies, and by comparing known details (usually from the skeleton, because that is the only thing available from most fossils).
Essentially they collect a lot of traits of many species. If you assume that more closely related species have more traits in common a computer program can then figure out the most likely evolutionary tree.
In that tree, anything in the bird branch below the "bird ancestor" node is a bird.
Richard Feynman - Names Don't Constitute Knowledge
&
Alan Watts: Bigger Wiggle
It seems those two have said something about which you are saying now: people by default try to understand by compartmentalizing ideas in little boxes. A lot of the time they don't even know what's in the box, they just know the name that's on it and what the stuff inside tends to look like.
That's just a shortcut we take to manage our limited resources.
Works for me. I've been to Tengchong twice over the last 16 years and it's a very interesting area historically: the British used to have a trading base there for Burma-China trade, and there is a lot of local geothermal activity, hot springs, lakes, old architecture, nature, etc. Relevant quotes from https://github.com/globalcitizen/taoup ...
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt. - Bertrand Russell (1950)
A smart machine is a profoundly paradoxical entity, but a paradox is not a supernatural act. A paradox is a symptom of a breakdown in two competing definitional systems. - Bruce Sterling (1995)
Once you've got some words looking back at you, you can take two or three — or throw them away and look for others. - Bernard Malamud
Writing is nature's way of letting you know how sloppy your thinking is. - Guindon
The main rule of writing is that if you do it with enough assurance and confidence, you're allowed to do whatever you like. - 'Neil Gaiman on open source', Peter Hilton
When I use a word, it means just what I choose it to mean - neither more nor less. - Humpty Dumpty ("in a rather scornful tone"), 'Through the Looking-Glass, and What Alice Found There' (1871), Lewis Carroll
A rose by any other name will end up as a cabbage. - Sam Gardiner
A language is a dialect with an army and a navy. - Max Weinreich
Words build bridges in to unexplored regions. - Adolf Hitler
Furious activity is no substitute for understanding. - H. H. Williams
Blind monkey at the typewriter. - Robert Burnham Jr., Astronomer (1983)
The change happened very gradually over millions of years. The answer to that question is similar to the Sorites paradox, or the paradox of the heap of sand.
If you have a heap of sand, and remove grains of sand one at a time, at which point does the heap stop being a heap?
Well according to many people birds today are dinosaurs. (they are indisputably members of "Dinosauria")
But as with pretty much everything, there would have been a long period where they were on the border of being birds. Categories in biology always have blurry boundaries. And those boundaries will of course adjust as we get more fossils and other information.
