This is probably two different subjects, but I'm guessing that the mechanics are the same.

 

Why do some spieces of birds (geese for example), always seem to fly in a triangle formation? How do they decide who leads the formation?

 

Lastly, how do schools of fish (sardines etc), and flocks of small birds, decide their next direction and is there a lead fish, or bird, as such?

Flocks of birds fly in a triangle because that fomation is easier. The lead bird creates turbulence in the air which helps the following birds to fly using less energy. When the lead bird gets tired it goes back and another replaces it (it's harder to fly lead).

The lead bird creates turbulence in the air which helps the following birds to fly using less energy. When the lead bird gets tired it goes back and another replaces it (it's harder to fly lead).

 

Reminds me of tour de france )

 

 

As far as school of fish are concerned, they tend to stay in schools so that its really hard to catch a single individual ( Its even hard in an aquarium forget open ocean ). The school tries to move as a single fish, so there may not be a single fish leading it but perhaps a bunch of them. How they manage to coordinate ? I have no idea

"Placement of eyes on the side of the head allows the fish to readily see what is next to them and move accordingly. However, sight is not the only factor used in schooling. Fish are able to establish their placement and direction in a school are by using hearing, lateral line, sight, and even the sense of smell. "

http://freshaquarium.about.com/cs/beginnerinfo/a/schooling.htm

Fish sense changes in water pressure with their lateral line. So they immediately detect when the fish next to them change direction.

Reminds me of tour de france )

The school tries to move as a single fish' date=' so there may not be a single fish leading it but perhaps a bunch of them. How they manage to coordinate ? I have no idea[/quote']

In schooling fish (e.g. mackerel) there is a direct physical link between mechanisms of perception and mechanisms of motor function. Percieved changes in relative velocity or direction of surrounding members of the school triggers a motor response that brings the individual 'into phase' with the school, i.e. attempts to eliminate the relative differences in velocity and direction between it and those surrounding it.

 

Humans also have this mechanism. Residual though it may be, you can still see examples of its action in human social interaction. It's called 'mirroring' behaviour.

 

You could check this out if you are interested:

 

Dijksterhuis, A., Bargh, J. A., & Miedema, J. (2000). Of men and mackerels: Attention, subjective experience, and automatic social behavior. In H. Bless & J. P. Forgas (Eds.), The message within: The role of subjective experience in social cognition and behavior (pp. 37-51). Philadelphia: Psychology Press/Taylor & Francis.