Random Entry of Object

At present I am developing Bird Hunting game in 2D.
For which I want to create animation like bird come into screen from random position.
I know about creating animation at design time but at present I want to create run time animation.

So how to achieve this? Small suggestion become enough for me.

The fastes way to do this, is to instantiate bird at random position and set his endPosition.

GameObject instantiatedBird=GameObject.Instantiate(birdPrefab,Random.insideUnitSphere,Quaternion.identity);

Then in BirdLogic you would do this

public Vector3 endPosition; // bird's target position
Vector3 startPosition;
float time=0; // 

void Start() {
	startPosition = transform.position; // remember start position
void Update() {
	time=Mathf.Clamp01(time); // make sure time is between 0 and 1
	transform.position = Vector3.Lerp(startPosition, endPosition, time);

If you wish to set the bird’s rotation according to the direction he moves, add this to the Update function:

transform.rotation = Quaternion.LookRotation(endPosition-transform.position);