Script error: OnCollisionEnter2D This message parameter has to be of type: Collision2D The message will be ignored.

Questions & Answers
1

Vector3 velocity = Vector3.zero;
public float flapSpeed = 50f;
public float forwardSpeed = 1f;

bool didFlap = false;

Animator animator;

bool dead = false;

// Use this for initialization
void Start () {
	animator = transform.GetComponentInChildren< Animator >();
	
	if( animator == null )
	{ Debug.LogError( "Unable to find Animator!" ); }

}

//Do Graphic & Input updates here
void Update(){
	if(Input.GetKeyDown(KeyCode.Space) || Input.GetMouseButtonDown(0)) {
		didFlap = true;

	}
}

// Do physics engine updates here
void FixedUpdate () {

	if (dead)
		return;

	gameObject.GetComponent<Rigidbody2D>().AddForce(Vector2.right * forwardSpeed);

	if(didFlap) {
		gameObject.GetComponent<Rigidbody2D>().AddForce(Vector2.up * flapSpeed);
		didFlap = false;
		animator.SetTrigger("DoFlap");

	}

	if(gameObject.GetComponent<Rigidbody2D>().velocity.y >0) {
		transform.rotation = Quaternion.Euler(0, 0, 0);
	}

	if(gameObject.GetComponent<Rigidbody2D>().velocity.y >0) {
		float angle = Mathf.Lerp(0, -25, -gameObject.GetComponent<Rigidbody2D>().velocity.y / 4f );
		transform.rotation = Quaternion.Euler(0, 0, angle);
	}

}
void OnCollisionEnter2D(Collider2D collision) {**ERROR**
	animator.SetTrigger("Death");**ERROR**
	dead = true;
}

}

2

As the error suggests you are using Collider2D instead of Collision2D as the parameter type for the OnCollisionEnter2D method, try:

void OnCollisionEnter2D(Collision2D collision) {
     animator.SetTrigger("Death");
     dead = true;
 }