re.another difficult question

Jerky motion apparently helps birds
monitor depth perception.  If it is close it will move faster than
a distant object. (Like posts next to the road flashing past when you are
driving a car, and the landscape in the distance moves slower.)

So tying in with your post Graeme, perhaps
the tail and jerky motion stirs up the insects and also allows birds to
judge the distance of the insects so they can catch them once stirred.

I think pied plumage helps heat distribution
and regulation, but this is just a guess. 

Peter

"Lyndy or Graeme" <>
Sent by:

25/02/2004 02:18 PM

To
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Subject	[BIRDING-AUS] re.another difficult question

We must think convergence and then functional values.
What habitat qualities 
may be the same for all locations which will select for black and white,
long tail, jerky motion? What fundtional values do these characters give?
Off the top of my head, water enables riparian vegetation which leads to
shade and light mottling. Maybe black and white is good camaflage for this
light condition.
Riparian veg. and water leads to insects. Jery motion may simply be good
for 
locating and catching small insects. Long tail may be a suitable morphology
for rapid direction change, jerky motion.
Or something completely different.
Graeme

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