Ignore collision at the start of the game.

I am trying to create a neuroevolution AI for flappy bird. The problem is when i create a population for 50 birds. They collide with each other at the start of the game. However i have ignored the collision through
the following code but it’s not working at the start.

private void OnCollisionEnter2D(Collision2D collision2D)
{

    if (collision2D.gameObject.tag == "ignore")
    {
        Physics2D.IgnoreCollision(collision2D.collider, gameObject.GetComponent<Collider2D>());
        return;
    }
    else
    {
        isDead = true;
        anim.SetTrigger("Die");
        Destroy(gameObject);
    }

    

}

Just found out the answer for it myself. I just replaced the collisionenter2d with triggerEnter2D. I guess trigger function is called before start.