ACTIVE AND PASSIVE FLIGHT , LOCOMOTION OF BIRDS IN AIR

There are Two Modes Of Flight :

1) Passive Flight

"The GLIDING of Birds Without the Utilization of Energy or little Utilization is Known As Passive Flight."

This process takes place through AEROFOILS 

What is Aerofoil?

Well , Aerofoil is a Smooth surface which can Move or traverse through air at a particular angle to the Airflow , Air Currents or AirStream.

The Wings act as Aerofoils in Passive Flight.The Pressure Gradient is developed such that The bird is given a lift.The Shape Of wings Matters , 

Narrow And Long wings can Behave or Act as Aerofoils .

The Birds Which undergo Passive Flight are : Seagulls,Eagles, Vultures,Storks e.t.c.

The Point worth Remembering is That The extent of the Lift depends upon The Angle Kept relative to the Airstream.

2)  Active Flight 

"The Flying Process due to the Utilization of Energy is Called Active Flight . A bird undergoes Active Flight when Air Currents can no longer support to lift the Body "

Why Do birds flap Wings ?

Birds flap Wings To generate Pressure gradient just like that of Passive Flight, but this time not by airstream , but by own effort.

As the Flapping proceeds, the air flows over the upper surface more fastly than the lower surface.

The Pressure Equation Of Physics say that:

"Where the pressure is low , the speed is high"

According to it , the Pressure Above the Wings decreases and The Body Gets The Lift due to net pressure acting upwards, present Below the wings .

The Wing shape matters here too.

The Birds Which cannot undergo Passive flight bave BROAD AND SHORT Wings.Examples are Garden Birds ,Parrots , Falcon e.t.c.