What's the deal with birds?

[KingMerv00]

Why do birds move the way they do?

Smaller birds like robins sparrows etc move with quick jerks, seemingly incapable of slow muscle movement while larger birds like owls can. What's the deal?

Why do chickens and pigeons bob their heads when they walk?

 

[Dr Adequate]

Why do chickens and pigeons bob their heads when they walk?

What a pigeon is doing there is holding its head still (w.r.t. to its surroundings) while it moves its body forwards. It then jerks its head quickly forwards to catch up. Presumably it makes things easier for its visual processing system if it keeps its head still most of the time.

 

[StaticEngine]

What I want to know is, since dinosaurs were so huge, why are birds so small?

I know, evolutionary pressures.

 

[Dr Adequate]

What I want to know is, since dinosaurs were so huge...

Not all of them were. Last I heard, the smallest known dinosaur is Compsognathus, which was no bigger than a chicken.

 

[El_Spectre]

Not all of them were. Last I heard, the smallest known dinosaur is Compsognathus, which was no bigger than a chicken.

I read somewhere (no, I don't have a source, sorry) that the little species actually outnumbered the big boys, but we just don't hear much about them.

Of course, the general public doesn't realize that there were several species of tyrannosaur, allosaur, etc.

 

[Eos of the Eons]

What I want to know is, since dinosaurs were so huge, why are birds so small?

I know, evolutionary pressures.

If Mammoths were so huge, then why are mice and bats so small? Look at the habitats and how they live. Then look at their food sources. How well can a large flying animal be supported in the world today? It's not really "evolutionary pressures" as much as it is environmental.

It makes sense that larger dinosaurs dissappeared first. Since mammals have filled the niches, there is no way larger reptiles can make such a huge comeback again.

The only true constant in that sense is change. The world changes, and animals must adapt or die.

 

[Soapy Sam]

I dunno, Eos- big crocodiles are doing very nicely, thanks- especially in OZ where they enjoy a diet of beef-fattened tourist.
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If we imagine all the mammals in the world, from heffelumps to shrews and suppose there was probably something dinosaurian analogous to most of them, then think about which would be more likely to be preserved for 100MY- a mouse skeleton , or an elephant one- (and there are arguments for both).
The truth is we have likely barely scratched the surface of the dinosaurs and the creatures they shared the world with. We have no real idea how many species or even genera appeared, flourished and vanished during their period of dominance.

And until very recently- historical times- there were many types of extremely big, flightless bird in the world.

And we all know what happens to big birds that can't fly, don't we , children?

 

[Eos of the Eons]

My T-Rex scoffs at your puny croc!

 

[epepke]

Why do birds move the way they do?

Smaller birds like robins sparrows etc move with quick jerks, seemingly incapable of slow muscle movement while larger birds like owls can. What's the deal?

Why do chickens and pigeons bob their heads when they walk?

I read a study on this once.

Birds with eyes on the side of their heads appear to use parallax to judge the distance of objects. The bobbing provides different points of view. Birds with eyes on the front have significant overlap and stereo vision.